International Journal of Molecular Sciences

17 pages, 3875 KiB

Open AccessArticle

Tal2c Activates the Expression of OsF3H_04g to Promote Infection as a Redundant TALE of Tal2b in Xanthomonas oryzae pv. oryzicola

by Tao Wu, Haimiao Zhang, Yunya Bi, Yue Yu, Haifeng Liu, Hong Yang, Bin Yuan, Xinhua Ding and Zhaohui Chu

Int. J. Mol. Sci. 2021, 22(24), 13628; https://doi.org/10.3390/ijms222413628 - 20 Dec 2021

Cited by 10 | Viewed by 2720

Abstract

Xanthomonas oryzae delivers transcription activator-like effectors (TALEs) into plant cells to facilitate infection. Following economic principles, the redundant TALEs are rarely identified in Xanthomonas. Previously, we identified the Tal2b, which activates the expression of the rice 2-oxoglutarate-dependent dioxygenase gene OsF3H_03g to promote [...] Read more.

Xanthomonas oryzae delivers transcription activator-like effectors (TALEs) into plant cells to facilitate infection. Following economic principles, the redundant TALEs are rarely identified in Xanthomonas. Previously, we identified the Tal2b, which activates the expression of the rice 2-oxoglutarate-dependent dioxygenase gene OsF3H_03g to promote infection in the highly virulent strain of X. oryzae pv. oryzicola HGA4. Here, we reveal that another clustered TALE, Tal2c, also functioned as a virulence factor to target rice OsF3H_04g, a homologue of OsF3H_03g. Transferring Tal2c into RS105 induced expression of OsF3H_04g to coincide with increased susceptibility in rice. Overexpressing OsF3H_04g caused higher susceptibility and less salicylic acid (SA) production compared to wild-type plants. Moreover, CRISPR–Cas9 system-mediated editing of the effector-binding element in the promoters of OsF3H_03g or OsF3H_04g was found to specifically enhance resistance to Tal2b- or Tal2c-transferring strains, but had no effect on resistance to either RS105 or HGA4. Furthermore, transcriptome analysis revealed that several reported SA-related and defense-related genes commonly altered expression in OsF3H_04g overexpression line compared with those identified in OsF3H_03g overexpression line. Overall, our results reveal a functional redundancy mechanism of pathogenic virulence in Xoc in which tandem Tal2b and Tal2c specifically target homologues of host genes to interfere with rice immunity by reducing SA. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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17 pages, 3891 KiB

Open AccessArticle

Disruption of OsPHD1, Encoding a UDP-Glucose Epimerase, Causes JA Accumulation and Enhanced Bacterial Blight Resistance in Rice

by Yu Gao, Xiaojiao Xiang, Yingxin Zhang, Yongrun Cao, Beifang Wang, Yue Zhang, Chen Wang, Min Jiang, Wenjing Duan, Daibo Chen, Xiaodeng Zhan, Shihua Cheng, Qunen Liu and Liyong Cao

Int. J. Mol. Sci. 2022, 23(2), 751; https://doi.org/10.3390/ijms23020751 - 11 Jan 2022

Cited by 6 | Viewed by 2176

Abstract

Lesion mimic mutants (LMMs) have been widely used in experiments in recent years for studying plant physiological mechanisms underlying programmed cell death (PCD) and defense responses. Here, we identified a lesion mimic mutant, lm212-1, which cloned the causal gene by a map-based [...] Read more.

Lesion mimic mutants (LMMs) have been widely used in experiments in recent years for studying plant physiological mechanisms underlying programmed cell death (PCD) and defense responses. Here, we identified a lesion mimic mutant, lm212-1, which cloned the causal gene by a map-based cloning strategy, and verified this by complementation. The causal gene, OsPHD1, encodes a UDP-glucose epimerase (UGE), and the OsPHD1 was located in the chloroplast. OsPHD1 was constitutively expressed in all organs, with higher expression in leaves and other green tissues. lm212-1 exhibited decreased chlorophyll content, and the chloroplast structure was destroyed. Histochemistry results indicated that H₂O₂ is highly accumulated and cell death is occurred around the lesions in lm212-1. Compared to the wild type, expression levels of defense-related genes were up-regulated, and resistance to bacterial pathogens Xanthomonas oryzae pv. oryzae (Xoo) was enhanced, indicating that the defense response was activated in lm212-1, ROS production was induced by flg22, and chitin treatment also showed the same result. Jasmonic acid (JA) and methyl jasmonate (MeJA) increased, and the JA signaling pathways appeared to be disordered in lm212-1. Additionally, the overexpression lines showed the same phenotype as the wild type. Overall, our findings demonstrate that OsPHD1 is involved in the regulation of PCD and defense response in rice. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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19 pages, 8473 KiB

Open AccessArticle

Salicylic Acid Is Required for Broad-Spectrum Disease Resistance in Rice

by Bingbing Liang, Han Wang, Ce Yang, Luyao Wang, Linlu Qi, Zejian Guo and Xujun Chen

Int. J. Mol. Sci. 2022, 23(3), 1354; https://doi.org/10.3390/ijms23031354 - 25 Jan 2022

Cited by 24 | Viewed by 4212

Abstract

Rice plants contain high basal levels of salicylic acid (SA), but some of their functions remain elusive. To elucidate the importance of SA homeostasis in rice immunity, we characterized four rice SA hydroxylase genes (OsSAHs) and verified their roles in SA [...] Read more.

Rice plants contain high basal levels of salicylic acid (SA), but some of their functions remain elusive. To elucidate the importance of SA homeostasis in rice immunity, we characterized four rice SA hydroxylase genes (OsSAHs) and verified their roles in SA metabolism and disease resistance. Recombinant OsSAH proteins catalyzed SA in vitro, while OsSAH3 protein showed only SA 5-hydroxylase (SA5H) activity, which was remarkably higher than that of other OsSAHs that presented both SA3H and SA5H activities. Amino acid substitutions revealed that three amino acids in the binding pocket affected SAH enzyme activity and/or specificity. Knockout OsSAH2 and OsSAH3 (sahKO) genes conferred enhanced resistance to both hemibiotrophic and necrotrophic pathogens, whereas overexpression of each OsSAH gene increased susceptibility to the pathogens. sahKO mutants showed increased SA and jasmonate levels compared to those of the wild type and OsSAH-overexpressing plants. Analysis of the OsSAH3 promoter indicated that its induction was mainly restricted around Magnaporthe oryzae infection sites. Taken together, our findings indicate that SA plays a vital role in immune signaling. Moreover, fine-tuning SA homeostasis through suppression of SA metabolism is an effective approach in studying broad-spectrum disease resistance in rice. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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11 pages, 1574 KiB

Open AccessArticle

Ac/Ds-Induced Receptor-like Kinase Genes Deletion Provides Broad-Spectrum Resistance to Bacterial Blight in Rice

by Qiong Mei, Yu Wen Fu, Tian Miao Li and Yuan Hu Xuan

Int. J. Mol. Sci. 2022, 23(9), 4561; https://doi.org/10.3390/ijms23094561 - 20 Apr 2022

Cited by 3 | Viewed by 2487

Abstract

Rice bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) seriously affects rice yield production. The discovery and application of broad-spectrum resistance genes are of great advance for disease resistance breeding. Previously, we identified that multiple receptor-like kinase (RLK) family gene [...] Read more.

Rice bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) seriously affects rice yield production. The discovery and application of broad-spectrum resistance genes are of great advance for disease resistance breeding. Previously, we identified that multiple receptor-like kinase (RLK) family gene deletions induced by the Ac/Ds system resulted in a lesion mimic symptom. In this study, the mutant #29 showed that this lesion mimic symptom was isolated. Further analysis identified that four RLK genes (RLK19-22) were deleted in the #29 mutant. The #29 mutant exhibited broad-spectrum resistance to Xoo and subsequent analyses identified that pathogenesis-related genes PR1a, PBZ1, and cellular H₂O₂ levels were significantly induced in the mutant compared to wild-type plants. A genetic analysis revealed that reconstruction of RLK20, RLK21, or RLK22 rescued the lesion mimic symptom of the #29 mutant, indicating that these three RLKs are responsible for broad-spectrum resistance in rice. Further yeast two hybrid and bimolecular fluorescence complementation assays demonstrated that RLK20 interacts with RBOHB, which is a ROS producer in plants. Compared to wild-type plants, the #29 mutant was more, while #29/RLK20ox was less, susceptible to MV (methyl-viologen), an ROS inducer. Co-expression of RLK20 and RBOHB reduced RBOHB-promoted H₂O₂ accumulation in the cells. Taken together, our research indicated that the RLKs may inhibit RBOHB activity to negatively regulate rice resistance to Xoo. These results provide the theoretical basis and valuable information about the target genes necessary for the successful breeding of rice cultivars resistant to bacterial blight. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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20 pages, 3124 KiB

Open AccessArticle

The Rice ILI2 Locus Is a Bidirectional Target of the African Xanthomonas oryzae pv. oryzae Major Transcription Activator-like Effector TalC but Does Not Contribute to Disease Susceptibility

by Hinda Doucouré, Florence Auguy, Servane Blanvillain-Baufumé, Sandrine Fabre, Marc Gabriel, Emilie Thomas, Fleur Dambreville, Coline Sciallano, Boris Szurek, Ousmane Koita, Valérie Verdier and Sébastien Cunnac

Int. J. Mol. Sci. 2022, 23(10), 5559; https://doi.org/10.3390/ijms23105559 - 16 May 2022

Cited by 2 | Viewed by 2302

Abstract

Xanthomonas oryzae pv. oryzae (Xoo) strains that cause bacterial leaf blight (BLB) limit rice (Oryza sativa) production and require breeding more resistant varieties. Transcription activator-like effectors (TALEs) activate transcription to promote leaf colonization by binding to specific plant host [...] Read more.

Xanthomonas oryzae pv. oryzae (Xoo) strains that cause bacterial leaf blight (BLB) limit rice (Oryza sativa) production and require breeding more resistant varieties. Transcription activator-like effectors (TALEs) activate transcription to promote leaf colonization by binding to specific plant host DNA sequences termed effector binding elements (EBEs). Xoo major TALEs universally target susceptibility genes of the SWEET transporter family. TALE-unresponsive alleles of clade III OsSWEET susceptibility gene promoter created with genome editing confer broad resistance on Asian Xoo strains. African Xoo strains rely primarily on the major TALE TalC, which targets OsSWEET14. Although the virulence of a talC mutant strain is severely impaired, abrogating OsSWEET14 induction with genome editing does not confer equivalent resistance on African Xoo. To address this contradiction, we postulated the existence of a TalC target susceptibility gene redundant with OsSWEET14. Bioinformatics analysis identified a rice locus named ATAC composed of the INCREASED LEAF INCLINATION 2 (ILI2) gene and a putative lncRNA that are shown to be bidirectionally upregulated in a TalC-dependent fashion. Gain-of-function approaches with designer TALEs inducing ATAC sequences did not complement the virulence of a Xoo strain defective for SWEET gene activation. While editing the TalC EBE at the ATAC loci compromised TalC-mediated induction, multiplex edited lines with mutations at the OsSWEET14 and ATAC loci remained essentially susceptible to African Xoo strains. Overall, this work indicates that ATAC is a probable TalC off-target locus but nonetheless documents the first example of divergent transcription activation by a native TALE during infection. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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19 pages, 6207 KiB

Open AccessArticle

Genome-Wide Association Study Identifies a Rice Panicle Blast Resistance Gene, Pb2, Encoding NLR Protein

by Yao Yu, Lu Ma, Xinying Wang, Zhi Zhao, Wei Wang, Yunxin Fan, Kunquan Liu, Tingting Jiang, Ziwei Xiong, Qisheng Song, Changqing Li, Panting Wang, Wenjing Ma, Huanan Xu, Xinyu Wang, Zijing Zhao, Jianfei Wang, Hongsheng Zhang and Yongmei Bao

Int. J. Mol. Sci. 2022, 23(10), 5668; https://doi.org/10.3390/ijms23105668 - 18 May 2022

Cited by 11 | Viewed by 2871

Abstract

Rice blast is one of the main diseases in rice and can occur in different rice growth stages. Due to the complicated procedure of panicle blast identification and instability of panicle blast infection influenced by the environment, most cloned rice resistance genes are [...] Read more.

Rice blast is one of the main diseases in rice and can occur in different rice growth stages. Due to the complicated procedure of panicle blast identification and instability of panicle blast infection influenced by the environment, most cloned rice resistance genes are associated with leaf blast. In this study, a rice panicle blast resistance gene, Pb2, was identified by genome-wide association mapping based on the panicle blast resistance phenotypes of 230 Rice Diversity Panel 1 (RDP1) accessions with 700,000 single-nucleotide polymorphism (SNP) markers. A genome-wide association study identified 18 panicle blast resistance loci (PBRL) within two years, including 9 reported loci and 2 repeated loci (PBRL2 and PBRL13, PBRL10 and PBRL18). Among them, the repeated locus (PBRL10 and PBRL18) was located in chromosome 11. By haplotype and expression analysis, one of the Nucleotide-binding domain and Leucine-rich Repeat (NLR) Pb2 genes was highly conserved in multiple resistant rice cultivars, and its expression was significantly upregulated after rice blast infection. Pb2 encodes a typical NBS-LRR protein with NB-ARC domain and LRR domain. Compared with wild type plants, the transgenic rice of Pb2 showed enhanced resistance to panicle and leaf blast with reduced lesion number. Subcellular localization of Pb2 showed that it is located on plasma membrane, and GUS tissue-staining observation found that Pb2 is highly expressed in grains, leaf tips and stem nodes. The Pb2 transgenic plants showed no difference in agronomic traits with wild type plants. It indicated that Pb2 could be useful for breeding of rice blast resistance. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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23 pages, 3771 KiB

Open AccessArticle

The Rice Malectin Regulates Plant Cell Death and Disease Resistance by Participating in Glycoprotein Quality Control

by Huijing Feng, Tiancheng Qiu, Changfa Yin, Xiaosheng Zhao, Guangyuan Xu, Linlu Qi, Yan Zhang, Youliang Peng and Wensheng Zhao

Int. J. Mol. Sci. 2022, 23(10), 5819; https://doi.org/10.3390/ijms23105819 - 22 May 2022

Cited by 6 | Viewed by 3007

Abstract

In animals, malectin is well known to play an essential role in endoplasmic reticulum quality control (ERQC) by interacting with ribophorin I, one unit of the oligosaccharyltransferase (OST) complex. However, the functions of malectin in plants remain largely unknown. Here, we demonstrate the [...] Read more.

In animals, malectin is well known to play an essential role in endoplasmic reticulum quality control (ERQC) by interacting with ribophorin I, one unit of the oligosaccharyltransferase (OST) complex. However, the functions of malectin in plants remain largely unknown. Here, we demonstrate the rice OsMLD1 is an ER- and Golgi-associated malectin protein and physically interacts with rice homolog of ribophorin I (OsRpn1), and its disruption leads to spontaneous lesion mimic lesions, enhanced disease resistance, and prolonged ER stress. In addition, there are many more N-glycosites and N-glycoproteins identified from the mld1 mutant than wildtype. Furthermore, OsSERK1 and OsSERK2, which have more N-glycosites in mld1, were demonstrated to interact with OsMLD1. OsMLD1 can suppress OsSERK1- or OsSERK2-induced cell death. Thus, OsMLD1 may play a similar role to its mammalian homologs in glycoprotein quality control, thereby regulating cell death and immunity of rice, which uncovers the function of malectin in plants. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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14 pages, 3036 KiB

Open AccessArticle

Cytokinin Confers Brown Planthopper Resistance by Elevating Jasmonic Acid Pathway in Rice

by Xiao Zhang, Daoming Liu, Dong Gao, Weining Zhao, Huaying Du, Zeyu Qiu, Jie Huang, Peizheng Wen, Yongsheng Wang, Qi Li, Wenhui Wang, Haosen Xu, Jun He, Yuqiang Liu and Jianmin Wan

Int. J. Mol. Sci. 2022, 23(11), 5946; https://doi.org/10.3390/ijms23115946 - 25 May 2022

Cited by 15 | Viewed by 2552

Abstract

Plants have evolved a sophisticated defense system that employs various hormone pathways to defend against attacks by insect pests. Cytokinin (CK) plays an important role in plant growth and stress tolerance, but the role of CKs in plant–insect interaction remains largely unclear. Here, [...] Read more.

Plants have evolved a sophisticated defense system that employs various hormone pathways to defend against attacks by insect pests. Cytokinin (CK) plays an important role in plant growth and stress tolerance, but the role of CKs in plant–insect interaction remains largely unclear. Here, we report that CKs act as a positive regulator in rice resistance against brown planthopper (BPH), a devastating insect pest of rice. We found that BPH feeding promotes CK biosynthesis and signaling in rice. Exogenous application of CKs significantly increased the rice resistance to BPH. Increasing endogenous CKs by knocking out cytokinin oxidase/dehydrogenase (OsCKXs) led to enhanced resistance to BPH. Moreover, the levels of the plant hormone jasmonic acid (JA) and the expression of JA-responsive genes were elevated by CK treatment and in OsCKXs knockout plants. Furthermore, JA-deficient mutant og1 was more susceptible to BPH, and CK-induced BPH resistance was suppressed in og1. These results indicate that CK-mediated BPH resistance is JA-dependent. Our findings provide the direct evidence for the novel role of CK in promoting insect resistance, and demonstrate that CK-induced insect resistance is JA-dependent. These results provide important guidance for effective pest management strategies in the future. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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15 pages, 2682 KiB

Open AccessArticle

Transcriptome Analysis Reveals Crosstalk between the Abscisic Acid and Jasmonic Acid Signaling Pathways in Rice-Mediated Defense against Nilaparvata lugens

by Jitong Li, Lin Chen, Xu Ding, Wenyan Fan and Jinglan Liu

Int. J. Mol. Sci. 2022, 23(11), 6319; https://doi.org/10.3390/ijms23116319 - 5 Jun 2022

Cited by 12 | Viewed by 2901

Abstract

The brown planthopper (BPH) impacts both rice yield and quality. The exogenous application of abscisic acid (ABA) and jasmonic acid (JA) has been previously shown to induce rice resistance to BPH; however, the regulation of rice-mediated defense by these plant growth regulators is [...] Read more.

The brown planthopper (BPH) impacts both rice yield and quality. The exogenous application of abscisic acid (ABA) and jasmonic acid (JA) has been previously shown to induce rice resistance to BPH; however, the regulation of rice-mediated defense by these plant growth regulators is unclear. We applied exogenous JA and ABA to rice and analyzed molecular responses to BPH infestation. Nine RNA libraries were sequenced, and 6218 differentially expressed genes (DEGs) were generated and annotated. After ABA + BPH and JA + BPH treatments, 3491 and 2727 DEGs, respectively, were identified when compared with the control (BPH alone). GO enrichment and KEGG pathway analysis showed that the expression of several JA pathway genes (OsAOS2, encoding allene oxide synthase; OsOPR, 12-oxo-phytodienoic acid reductase; and OsACOX, acy1-CoA oxidase) were significantly up-regulated after ABA + BPH treatment. Furthermore, exogenous JA increased the expression of genes involved in ABA synthesis. Meanwhile, the expression levels of genes encoding WRKY transcription factors, myelocytomatosis protein 2 (MYC2) and basic leucine zippers (bZIPs) were up-regulated significantly, indicating that ABA and JA might function together to increase the expression of transcription factors during the rice defense response. The DEGs identified in this study provide vital insights into the synergism between ABA and JA and further contribute to the mechanistic basis of rice resistance to BPH. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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11 pages, 2411 KiB

Open AccessArticle

Overexpression of OsGF14f Enhances Quantitative Leaf Blast and Bacterial Blight Resistance in Rice

by Yamei Ma, Jianyuan Yang, Jingfang Dong, Shaohong Zhang, Wu Yang, Junliang Zhao, Tifeng Yang, Luo Chen, Lian Zhou, Jian Wang, Jiansong Chen, Wenhui Li, Wei Wu, Qing Liu and Bin Liu

Int. J. Mol. Sci. 2022, 23(13), 7440; https://doi.org/10.3390/ijms23137440 - 4 Jul 2022

Cited by 4 | Viewed by 1967

Abstract

Although it is known that rice 14-3-3 family genes are involved in various defense responses, the functions of OsGF14f in response to diseases have not been reported. Here, we showed that the transcription of OsGF14f was significantly induced by leaf blast infection, and [...] Read more.

Although it is known that rice 14-3-3 family genes are involved in various defense responses, the functions of OsGF14f in response to diseases have not been reported. Here, we showed that the transcription of OsGF14f was significantly induced by leaf blast infection, and the overexpression of OsGF14f quantitatively enhanced resistance to leaf blast and bacterial blight in rice. Further analysis showed that the expression levels of salicylic acid (SA) pathway-associated genes (PAL1, NH1, PR1a and PR10) in the OsGF14f-overexpressing plants, were higher than those in wild-type plants after inoculation with the blast isolate (Magnaporthe oryzae Barr). In addition, the expression level of OsGF14f was significantly induced after SA treatment, and higher endogenous SA levels were observed in the OsGF14f-overexpressing plants compared with that in wild-type plants, especially after blast challenge. Taken together, these results suggest that OsGF14f positively regulates leaf blast and bacterial blight resistance in rice via the SA-dependent signaling pathway. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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12 pages, 1607 KiB

Open AccessArticle

Malectin Domain Protein Kinase (MDPK) Promotes Rice Resistance to Sheath Blight via IDD12, IDD13, and IDD14

by Zhibo Cui, Caiyun Xue, Qiong Mei and Yuanhu Xuan

Int. J. Mol. Sci. 2022, 23(15), 8214; https://doi.org/10.3390/ijms23158214 - 26 Jul 2022

Cited by 4 | Viewed by 2146

Abstract

Sheath blight (ShB) caused by Rhizoctonia solani is a major disease of rice, seriously affecting yield; however, the molecular defense mechanism against ShB remains unclear. A previous transcriptome analysis of rice identified that R. solani inoculation significantly induced MDPK. Genetic studies using [...] Read more.

Sheath blight (ShB) caused by Rhizoctonia solani is a major disease of rice, seriously affecting yield; however, the molecular defense mechanism against ShB remains unclear. A previous transcriptome analysis of rice identified that R. solani inoculation significantly induced MDPK. Genetic studies using MDPK RNAi and overexpressing plants identified that MDPK positively regulates ShB resistance. This MDPK protein was found localized in the endoplasmic reticulum (ER) and Golgi apparatus. Yeast one-hybrid assay, electrophoresis mobility shift assay (EMSA), and chromatin immunoprecipitation (ChIP) showed that the intermediate domain proteins IDD12, IDD13, and IDD14 bind to the MDPK promoter. Moreover, IDD14 was found to interact with IDD12 and IDD13 to form a transcription complex to activate MDPK expression. The three IDDs demonstrated an additive effect on MDPK activation. Further genetic studies showed that the IDD13 and IDD14 single mutants were more susceptible to ShB but not IDD12, while IDD12, IDD13, and IDD14 overexpressing plants were less susceptible than the wild-type plants. The IDD12, IDD13, and IDD14 mutants also proved the additive effect of the three IDDs on MDPK expression, which regulates ShB resistance in rice. Notably, MDPK overexpression maintained normal yield levels in rice. Thus, our study proves that IDD12, IDD13, and IDD14 activate MDPK to enhance ShB resistance in rice. These results improve our knowledge of rice defense mechanisms and provide a valuable marker for resistance breeding. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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14 pages, 2043 KiB

Open AccessArticle

Nanosheet-Facilitated Spray Delivery of dsRNAs Represents a Potential Tool to Control Rhizoctonia solani Infection

by Xijun Chen, Tong Shi, Tao Tang, Chen Chen, You Liang and Shimin Zuo

Int. J. Mol. Sci. 2022, 23(21), 12922; https://doi.org/10.3390/ijms232112922 - 26 Oct 2022

Cited by 8 | Viewed by 2220

Abstract

Rhizoctonia solani is one of the important pathogenic fungi causing several serious crop diseases, such as maize and rice sheath blight. Current methods used to control the disease mainly depend on spraying fungicides because there is no immunity or high resistance available in [...] Read more.

Rhizoctonia solani is one of the important pathogenic fungi causing several serious crop diseases, such as maize and rice sheath blight. Current methods used to control the disease mainly depend on spraying fungicides because there is no immunity or high resistance available in crops. Spraying double-strand RNA (dsRNA) for induced-gene silencing (SIGS) is a new potentially sustainable and environmentally friendly tool to control plant diseases. Here, we found that fluorescein-labelled EGFP-dsRNA could be absorbed by R. solani in co-incubation. Furthermore, three dsRNAs, each targeting one of pathogenicity-related genes, RsPG1, RsCATA, and RsCRZ1, significantly downregulated the transcript levels of the target genes after co-incubation, leading to a significant reduction in the pathogenicity of the fungus. Only the spray of RsCRZ1 dsRNA, but not RsPG1 or RsCATA dsRNA, affected fungal sclerotium formation. dsRNA stability on leaf surfaces and its efficiency in entering leaf cells were significantly improved when dsRNAs were loaded on layered double hydroxide (LDH) nanosheets. Notably, the RsCRZ1-dsRNA-LDH approach showed stronger and more lasting effects than using RsCRZ1-dsRNA alone in controlling pathogen development. Together, this study provides a new potential method to control crop diseases caused by R. solani. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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16 pages, 4841 KiB

Open AccessArticle

Genome-Wide Association Study Identifies a Rice Panicle Blast Resistance Gene Pb3 Encoding NLR Protein

by Lu Ma, Yao Yu, Changqing Li, Panting Wang, Kunquan Liu, Wenjing Ma, Wei Wang, Yunxin Fan, Ziwei Xiong, Tingting Jiang, Jingran Zhang, Zhixue Wang, Jianfei Wang, Hongsheng Zhang and Yongmei Bao

Int. J. Mol. Sci. 2022, 23(22), 14032; https://doi.org/10.3390/ijms232214032 - 14 Nov 2022

Cited by 9 | Viewed by 2472

Abstract

Rice blast is a worldwide fungal disease that seriously affects the yield and quality of rice. Identification of resistance genes against rice blast disease is one of the effective ways to control this disease. However, panicle blast resistance genes, which are useful in [...] Read more.

Rice blast is a worldwide fungal disease that seriously affects the yield and quality of rice. Identification of resistance genes against rice blast disease is one of the effective ways to control this disease. However, panicle blast resistance genes, which are useful in the fields, have rarely been studied due to the difficulty in phenotypic identification and the environmental influences. Here, panicle blast resistance-3 (Pb3) was identified by a genome-wide association study (GWAS) based on the panicle blast resistance phenotypes of 230 Rice Diversity Panel I (RDP-I) accessions with 700,000 single-nucleotide polymorphism (SNP) markers. A total of 16 panicle blast resistance loci (PBRLs) within three years including one repeated locus PBRL3 located in chromosome 11 were identified. In addition, 7 genes in PBRL3 were identified as candidate genes by haplotype analysis, which showed significant differences between resistant and susceptible varieties. Among them, one nucleotide-binding domain and Leucine-rich Repeat (NLR) gene Pb3 was highly conserved in multiple resistant rice cultivars, and its expression was significantly induced after rice blast inoculation. Evolutionary analysis showed that Pb3 was a typical disease resistance gene containing coiled-coil, NB-ARC, and LRR domains. T-DNA insertion mutants and CRISPR lines of Pb3 showed significantly reduced panicle blast resistance. These results indicate that Pb3 is a panicle blast resistance gene and GWAS is a rapid method for identifying panicle blast resistance in rice. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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17 pages, 2385 KiB

Open AccessArticle

Identification of Elite R-Gene Combinations against Blast Disease in Geng Rice Varieties

by Peng Gao, Mingyou Li, Xiaoqiu Wang, Zhiwen Xu, Keting Wu, Quanyi Sun, Haibo Du, Muhammad Usama Younas, Yi Zhang, Zhiming Feng, Keming Hu, Zongxiang Chen and Shimin Zuo

Int. J. Mol. Sci. 2023, 24(4), 3984; https://doi.org/10.3390/ijms24043984 - 16 Feb 2023

Cited by 7 | Viewed by 1935

Abstract

Rice blast, caused by the Magnaporthe oryzae fungus, is one of the most devastating rice diseases worldwide. Developing resistant varieties by pyramiding different blast resistance (R) genes is an effective approach to control the disease. However, due to complex interactions among [...] Read more.

Rice blast, caused by the Magnaporthe oryzae fungus, is one of the most devastating rice diseases worldwide. Developing resistant varieties by pyramiding different blast resistance (R) genes is an effective approach to control the disease. However, due to complex interactions among R genes and crop genetic backgrounds, different R-gene combinations may have varying effects on resistance. Here, we report the identification of two core R-gene combinations that will benefit the improvement of Geng (Japonica) rice blast resistance. We first evaluated 68 Geng rice cultivars at seedling stage by challenging with 58 M. oryzae isolates. To evaluate panicle blast resistance, we inoculated 190 Geng rice cultivars at boosting stage with five groups of mixed conidial suspensions (MCSs), with each containing 5–6 isolates. More than 60% cultivars displayed moderate or lower levels of susceptibility to panicle blast against the five MCSs. Most cultivars contained two to six R genes detected by the functional markers corresponding to 18 known R genes. Through multinomial logistics regression analysis, we found that Pi-zt, Pita, Pi3/5/I, and Pikh loci contributed significantly to seedling blast resistance, and Pita, Pi3/5/i, Pia, and Pit contributed significantly to panicle blast resistance. For gene combinations, Pita+Pi3/5/i and Pita+Pia yielded more stable pyramiding effects on panicle blast resistance against all five MCSs and were designated as core R-gene combinations. Up to 51.6% Geng cultivars in the Jiangsu area contained Pita, but less than 30% harbored either Pia or Pi3/5/i, leading to less cultivars containing Pita+Pia (15.8%) or Pita+Pi3/5/i (5.8%). Only a few varieties simultaneously contained Pia and Pi3/5/i, implying the opportunity to use hybrid breeding procedures to efficiently generate varieties with either Pita+Pia or Pita+Pi3/5/i. This study provides valuable information for breeders to develop Geng rice cultivars with high resistance to blast, especially panicle blast. Full article

(This article belongs to the Special Issue Molecular Genetics of Rice Disease Resistance)

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