Search Results (97)

Male sterility is an important trait in heterosis utilization and marigold (Tagetes erecta L.) breeding. Currently, most male-sterile lines used in production are derived from natural mutations. ABORTED MICROSPORES (AMS) is an important gene that regulates tapetum and microspore development. Therefore, the effect of AMS on fertility was studied. TeAMS was located in the nucleus and exhibited self-activation activity. TeAMS was highly expressed in the flower buds of T. erecta. The expression of this gene in fertile plants was higher than that in sterile plants, and the expression level gradually increased with the development of flower buds. The expression level of TeAMS was highest in the flower buds with a diameter of 1.2 cm at the floret differentiation stage, while the expression level was extremely low in the flower buds with a diameter of 1.6 cm. The expression trend of TeAMS in sterile plants was opposite to that in fertile plants. At the inflorescence primordium differentiation stage, flower buds with a diameter of 0.2 cm had the highest expression level, and the stem tip had the lowest expression level. In tobacco (Nicotiana tabacum L.), overexpression of the TeAMS gene resulted in shortened floral tubes, increased thousand-seed weight, a reduced flowering period, and decreased flower numbers. The pollen viability of transgenic tobacco was significantly lower than that of the wild type, and the pollen grains were smaller and showed irregular shapes. The pollen wall was dry and shrunk. Some pollen germinal furrows were distorted, and a few were almost invisible. Silencing TeAMS resulted in a longer flowering period in tobacco, reduced thousand-seed weight, and high pollen viability. Pollen morphology in silenced lines showed no significant differences compared to the wild-type and empty vector controls. Only a few pollen grains were smaller, shriveled, and shrunken. Therefore, the TeAMS gene plays an important role in regulating the fertility of marigolds. This study provides a theoretical foundation for breeding marigold male-sterile lines. Full article

Ogura cytoplasmic male sterility (CMS) in Chinese cabbage (Brassica rapa) is characterized by complete pollen abortion, wherein stamens fail to produce viable pollen while pistils retain normal fertility. This maternally inherited trait is valuable for hybrid breeding. This study employed integrated analysis of miRNA, transcriptome, and degradome sequencing data aligned to the Chinese cabbage reference genome to elucidate the molecular function of bra-miR9569 in Ogura CMS pollen fertility and explore its associated pathways. Subsequently, a bra-miR9569 overexpression vector was constructed and transformed into Arabidopsis thaliana. Phenotypic characterization of transgenic Arabidopsis lines, combined with anther viability assessment and quantification of ATP content and reactive oxygen species (ROS) levels in Chinese cabbage, was performed to analyze the effects of bra-miR9569. Our findings demonstrate that mutation of the mitochondrial gene orf138 in Ogura CMS lines leads to upregulation of bra-miR9569. This microRNA negatively regulates the expression of the ATP-related gene AHA6, resulting in reduced H⁺-ATPase activity. The consequent energy deficiency triggers cellular content degradation, ultimately causing failure of pollen wall formation and pollen abortion. Full article

To elucidate the molecular mechanisms underlying anther abortion in celery male sterile lines, this study investigates the morphological differences of floral organs and differential gene expression patterns between two lines at the flowering stage. Using the male sterile line of celery ‘QCBU-001’ and the fertile line ‘Jinnan Shiqin’ as materials, anther structure was analyzed by paraffin sections, and related genes were detected using transcriptome sequencing and qRT-PCR. The results indicated that the anther locules were severely shrunken at maturity in the sterile lines. The callose deficiency led to abnormal development of microspores, preventing the formation of mature pollen grains and ultimately leading to complete anther abortion. The transcriptome results revealed that 3246 genes were differentially expressed in sterile and fertile lines, which were significantly enriched in pathways such as starch and sucrose metabolism and phenylpropanoid biosynthesis. Additionally, differential expression patterns of transcription factor families (MYB, bHLH, AP2, GRAS, and others) suggested their potential involvement in regulating anther abortion. Notably, the expression level of callose synthase gene AgGSL2 was significantly downregulated in sterile anthers, which might be an important cause of callose deficiency and pollen sterility. This study not only provides a theoretical basis for elucidating the molecular mechanism underlying male sterility in celery but also lays a foundation for the utilization and improvement of male sterile lines in vegetable hybrid breeding. Full article

N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) and N-phenyl-1,2,3-thidiazole-5ylurea (TDZ) are plant growth regulators used for seedless treatment in grape. In this study, the flowers of ‘Shine Muscat’ (Vitis labruscana Bailey × V. vinifera L.) were treated with 3, 5, and 10 mg/L CPPU and TDZ one week before flowering. The results showed that both CPPU and TDZ treatments reduced the pollen germination rate and caused abnormal stamen and pollen grain phenotypes, resembling the male sterility observed in ‘Y_14’ (a novel grapevine germplasm derived from the self-progeny of ‘Shine Muscat’). Using RNA-seq technology, the stamens of flowers treated with 10 mg/L CPPU (CPPU_10), 10 mg/L TDZ (TDZ_10), and the control (CK) were analyzed. A total of 520 and 722 differentially expressed genes (DEGs) were identified in CPPU and TDZ treatments, respectively. GO and KEGG analyses revealed that the common pathways leading to pollen abortion in both treatments were primarily associated with hydrolase activity (acting on glycosyl bonds), phenylpropanoid biosynthesis, pentose and glucuronate interconversions, and ABC transporters. By comparing the DEGs across the three groups (Y_14 vs. SM, CPPU_10 vs. CK, TDZ_10 vs. CK), 16 DEGs exhibited similar expression patterns. Further tissue-specific expression analysis identified nine genes that were highly expressed in stamens and shared the same expression pattern in sterile lines. These findings provide a foundation for further studies on the impact of CPPU and TDZ treatments on grape stamen fertility. Full article

Background: The aim of this study was to develop a genetic transformation system to construct an overexpression vector for the mitochondrial gene atp6 in tobacco, thereby providing a foundation to investigate the functional roles of mitochondrial genes in this species. Methods: A full-length coding sequence (CDS) of the atp6 gene from a sterile line was cloned, along with the mitochondrial leader peptide sequence of atp2-1 from tobacco, using cDNA from kenaf UG93A anthers as a template. An overexpression vector for plants was constructed by employing In-Fusion technology, and wild-type tobacco plants were transformed via Agrobacterium-mediated transformation. Transgenic tobacco plants were then subjected to resistance screening and PCR validation. Results: The overexpression vector PBI121-atp2-1-atp6-EGFP, which includeds the mitochondrial leader peptide sequence, was successfully constructed. PCR validation using two pairs of primers targeting different sites on the overexpression vector confirmed the stable expression of the target gene in six transgenic tobacco plants (H1, H3, H4, H5, H7, and H8) via both primer pairs. A phenotypic analysis and iodine–potassium iodide (I₂-KI) staining of pollen grains from transgenic tobacco plants revealed the presence of shriveled and malformed pollen grains with reduced viability. These findings suggest that the atp6A gene, including the mitochondrial signal peptide, induces pollen abortion in tobacco. Conclusions: The genetic transformation system developed for the vector overexpressing the atp6 mitochondrial gene from kenaf provides a valuable framework to investigate the molecular regulatory mechanisms underlying the role of the atp6 gene in kenaf cytoplasmic male sterility (CMS). Full article

Lilies are one of the most popular ornamental flowers in the world. However, the abundant pollen produced in their anthers causes significant inconvenience for producers and consumers. Pollen abortion induced by molecular breeding techniques is one of the effective ways to solve this problem. In this study, the LoTDF1 gene, which is involved in regulating lily anther development, was identified and cloned from lily anthers based on transcriptome data. The open reading frame of LoTDF1 is 936 bp and encodes a protein with 311 amino acids. Multiple sequence alignment and phylogenetic tree analysis revealed that the LoTDF1 protein contained a conserved R2R3 domain, belonging to the MYB transcription factor family. Subcellular localization and transcriptional activation assays demonstrated that LoTDF1 localized to the nucleus and functioned as a transcription activator. The transcriptional activation domain was located within the last 195 amino acids (117–311a) of the C-terminus, and there may be more than one transcriptional activation domain in the region. The expression level of the LoTDF1 gene was highest during the pollen mother cell (PMC) stage of lily anther development (2 cm anther), followed by the tetrad stage (4 cm anther). In situ hybridization experiments further confirmed that LoTDF1 transcripts were predominantly localized in PMCs, tapetal cells, middle layer cells, dyads, and tetrads. The experiment data suggest that LoTDF1 plays a critical role in regulating early anther development in lily. LoTDF1 could be a promising candidate gene for molecular breeding strategies aimed at developing pollen-free lily cultivars to enhance commercial and consumer appeal. Full article

Paeonia ludlowii is a threatened and valuable germplasm in the cultivated tree peony gene pool, with distinctive traits such as tall stature, pure yellow flowers, and scarlet foliage in autumn. However, the crossability barrier limits gene transfer from P. ludlowii to cultivated tree peony. Therefore, our study investigated the reasons for the lack of crossability between P. ludlowii and Paeonia ostii ‘Fengdan’. Distant cross pollination (DH) resulted in the formation of many calloses at the ends of the pollen tubes, which grew non-polar, twisted, entangled, and often stopped in the style. Pollen tubes elongated the fastest in self-pollination (CK), and pollen tubes elongated faster and fewer pollen tube abnormalities were observed in stigmas treated with KCl solution before pollination (KH) than in DH. During pollen–pistil interactions, the absence of stigma exudates, high levels of H₂O₂, O₂⁻, MDA, ^•OH, ABA, and MeJA, and lower levels of BR and GA₃ may negatively affect pollen germination and pollen tube elongation in the pistil of P. ostii ‘Fengdan’. Pollen tubes in CK and KH penetrated the ovule into the embryo sac at 24 h after pollination, whereas only a few pollen tubes in DH penetrated the ovule at 36 h after pollination. Pre-embryo abnormalities and the inhibition of free nuclear endosperm division resulted in embryo abortion in most of the fruits of DH and many fruits of KH, which occurred between 10 and 20 days after pollination, whereas embryos in CK developed well. Early embryo abortion and endosperm abortion in most of the fruits of DH and KH led to seed abortion. Seed abortion in KH and DH was mainly due to an insufficient supply of auxins and gibberellins and lower content of soluble protein and soluble sugars. The cross failure between P. ludlowii and P. ostii ‘Fengdan’ is mostly caused by a pre-fertilization barrier. KH treatment can effectively promote pollen tube growth and facilitate normal development of hybrid embryos. These findings provide new insights into overcoming the interspecific hybridization barrier between cultivated tree peony varieties and wild species. Full article

Cocoa (Theobroma cacao L.) relies on insect pollination for fruit production, making it essential to understand the pollinators involved. This study aimed to identify the insects associated with cocoa pollination and their relationship with effective natural pollination in a cocoa agroforestry system in Yopal, Colombia. Indirect (wood traps) and direct (manual aspiration in flowers) methods were used to capture pollinators. The number of captured insects was correlated with the percentage of pollinated, fertilized, aborted, and transitioning flowers using Pearson’s correlation coefficient. Additionally, the natural transfer of pollen was assessed by evaluating the coverage of near-opening flowers and staining pollen grains on the stigma under natural conditions. This study identified Diptera from the Ceratopogonidae family, specifically the genera Forcipomyia and Dasyhelea, as key pollinators. The findings highlight the presence of these pollinators in the Yopal cocoa agroforestry system and suggest the need for further pollinator capture and identification efforts on local farms. A positive correlation was found between the number of pollinating insects and the percentage of fertilized flowers, emphasizing the crucial role of these insects in cocoa pollination and the importance of promoting their presence to optimize fruit production. Full article

Salinity negatively affects flower production and fertility in tomato but the underlying mechanisms are not fully understood. One hypothesis is that salinity affects sugar partitioning by reducing photosynthesis, which in turn affects source–sink relationships and hence the development of reproductive structures. This study investigates how salt stress alters sugar composition in leaves, flowers, and phloem sap of Solanum lycopersicum and its halophyte relative Solanum chilense, and how this may explain the effects on flower production and fertility. Salt stress increased flower abortion and reduced sepal length in S. lycopersicum, while decreasing pollen grain number in S. chilense. Photosynthetic nitrogen use efficiency was also reduced in S. lycopersicum. Salinity raised myo-inositol and sucrose concentrations in S. lycopersicum leaves but only slightly altered sugar concentrations in flowers. The concentration of sucrose in the foliar exudates was higher in S. chilense as compared to S. lycopersicum, suggesting a higher export of sucrose from the leaves. These findings suggest that S. lycopersicum maintains better metabolic function under salt stress, while S. chilense sustains sugar import to sink organs. Correlations between reproductive traits and sugar dynamics indicate that sugar distribution contributes to reproductive development under salinity stress. Full article

Cytoplasmic male sterility (CMS) and dominant genic male sterility (DGMS) both result in the inability to produce or release functional pollen, making them pivotal systems in the hybridization breeding programs of Brassica crops such as cabbage (B. oleracea var. capitata). However, the underling molecular mechanisms are still largely unexplored. This study integrated transcriptomic and metabolomic analyses of cabbage DGMS line, Ogura CMS line, and the maintainer line to uncover the molecular mechanisms underlying these sterility types. The joint analysis predominantly identified significantly enriched pathways, including carbohydrate metabolism, flavonoid biosynthesis, and phenylpropanoid pathways between the MS lines and the maintainer. Especially, the CMS line exhibited a broader range of metabolic perturbations, with a total of 3556 significantly differentially expressed genes (DEGs) and 439 differentially accumulated metabolites (DAMs) detected, particularly in the vitamin B6 metabolism pathway, which showed significant alterations. Given the differences in the inactivation period of microspores in CMS and DGMS lines, we found that DEGs unique to DGMS and maintainer line, such as BoGRPs and BoLTPs, primarily regulate fertility development before the unicellular stage. The DEGs shared between CMS_vs_maintainer and DGMS_vs_maintainer mainly govern microspore development after release from the tetrad, such as BoHXK1 and BoIDH. Additionally, the DEGs unique to CMS_vs_maintainer may contribute to other damage in floral organs beyond male fertility, potentially leading to severe bud abortion, such as BoPNPO. These findings provide a comprehensive framework for understanding the molecular mechanisms of male sterility and offer valuable insights into future breeding strategies in cruciferous vegetables. Full article

Olive (Olea europaea L.) trees produce many more flowers than fruit. In an “on” year, an adult olive tree may produce as many as 500,000 flowers, but 98% of them will drop soon after bloom as unfertilized flowers or juvenile fruit. This waste of resources that could be better invested in fruit reaching maturation requires an explanation. Several, not mutually exclusive, hypotheses explaining the possible significance of heavy flowering followed by massive and premature flower and fruit abscission are analyzed and compared based on previously published works and recent observations on olive reproductive biology. The results suggest that olive trees selectively abort fruits to enhance the quality of the seeds in the surviving fruits. Additionally, a considerable proportion of flowers appears to contribute to the male fitness of the plant by increasing pollen export. Conversely, the hypotheses attributing to resource limitation, pollination deficits, pollinator attraction, or extra flowers functioning as an ovary reserve, must be rejected for explaining the ultimate functions of massive flower production. Implications for olive orchard management are discussed. Full article

Cytoplasmic male sterile (CMS) systems have great potential in hybrid seed production in many plants. However, the incompatibility between the cytoplasmic and nuclear genes and the availability of fewer CMS lines limit the system’s application in cotton heterosis. Therefore, the present study sequenced the mitochondrial (mt) genomes of a novel cotton (Gossypium hirsutum L.) CMS line J4A and its cytoplasmic nuclear homologous maintainer line J4B to investigate the mechanism underlying CMS and improve its application. A novel CMS gene, orf116b, was identified in the CMS line. Ectopic expression of orf116b in Escherichia coli suppressed growth, while its overexpression in Arabidopsis, rice, tobacco, and cotton led to complete or partial male sterility. Further analysis of anthers revealed mt disruption in J4A with higher levels of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), but lower levels of ATP and ribosomal protein (RP) than in J4B. Finally, a membrane-based yeast two-hybrid (MYTH) assay and bimolecular fluorescence complementation (BiFC) assays demonstrated that orf116b probably interacts with an anther-specific protein, LAT52. These observations collectively proved that orf116b is associated with early and stable pollen abortion in cotton, providing a foundation for further research on cotton fertility restoration and heterosis breeding. Full article

×Leymotrigia bergrothii is a presumed hybrid of Leymus arenarius and Elytrigia repens. This article investigates the hybrid origin and genome composition of this species. These plants are sterile, do not undergo pollination, and do not produce seeds; occasionally, underdeveloped stamens containing abortive pollen grains form in individual spikelets. The karyotype analysis of root meristem cells revealed a diploid chromosome number of 49 in ×L. bergrothii, reported here for the first time. Subsequently, we examined the intragenomic polymorphism of the transcribed spacer ITS1 in several species of Elytrigia, Elymus, Leymus, Hordeum, and Psathyrostachys, and compared the ribotype patterns of these species with those of ×L. bergrothii. It is shown that the St-ribotype variants found in Elytrigia repens and Elytrigia pseudocaesia, as well as the ribotypes of the La family, which dominate in the genome of Leymus arenarius, correspond to major ribotypes in ×L. bergrothii. The ribotypes of the St and La families are present in the nuclear genome of ×L. bergrothii in almost equal proportions. A comparison of intron and exon sequences of the trnL gene in the chloroplast DNA of Leymus arenarius, Elytrigia repens, and ×L. bergrothii showed that this region in ×L. bergrothii is identical or very close to that of Elytrigia repens, suggesting that Elytrigia repens was the cytoplasmic donor to ×L. bergrothii. Thus, our study confirms the hypothesis that this species represents a sterile first-generation hybrid of Leymus arenarius and Elytrigia repens, reproducing vegetatively. Full article

Male sterility (MS) caused by aborted pollen is a vital germplasm resource. In this study, metabolomic, transcriptomic, and proteomic analyses were performed to investigate the molecular regulatory mechanism of cytoplasmic male sterility (CMS) in the flower buds of the male sterile line 09-05A and its maintainer line, 09-05B, of Brassica juncea. Our metabolomic analysis revealed that 41 metabolites involved in pollen development and male fertility formation were differentially accumulated between 09-05A and 09-05B at the bi-nucleate stage of B. juncea. Integrated omics indicated that the expression of key genes and proteins in the amino acid and phenylpropanoid metabolic pathways was remarkably downregulated in the flower buds of 09-05A. Furthermore, the abnormal expression of key transcription factor (TF) genes related to tapetum development and pollen wall formation may affect pollen development in the 09-05A CMS line. The results indicated that the downregulated expression level of critical genes and proteins in amino acid metabolism; phenylpropanoid synthesis; and TF genes, such as shikimate kinase, phenylalanine ammonia-lyase, and MYB103, may have led to impaired tapetum and pollen wall development, thereby causing pollen abortion in 09-05A. This study provides new insights into the metabolic and molecular regulatory mechanisms underlying the formation of CMS in B. juncea and lays a foundation for detailed studies on the identity and characteristics of MS-related genes. Full article

The pollen wall protects pollen during dispersal and is critical for pollination recognition. In the Poaceae family, the pollen exine stereostructure exhibits a high degree of conservation with similar patterns across species. However, there remains controversy regarding the conservation of key factors involved in its formation among various Poaceae species. EPAD1, as a gene specific to the Poaceae family, and its orthologous genes play a conserved role in pollen wall formation in wheat and rice. However, they do not appear to have significant functions in maize. To further confirm the conserved function of EPAD1 in Poaceae, we performed an analysis on four EPAD1 orthologs from two distinct sub-clades within the Poaceae family. The two functional redundant barley EPAD1 genes (HvEPAD1 and HvEPAD2) from the BOP clade, along with the single copy of sorghum (SbEPAD1) and millet (SiEPAD1) from the PACMAD clade were examined. The CRISPR-Cas9-generated mutants all exhibited defects in pollen wall formation, consistent with previous findings on EPAD1 in rice and wheat. Interestingly, in barley, hvepad2 single mutant also showed apical spikelets abortion, aligning with a decreased expression level of HvEPAD1 and HvEPAD2 from the apical to the bottom of the spike. Our finding provides evidence that EPAD1 orthologs contribute to Poaceae specific pollen exine pattern formation via maintaining primexine integrity despite potential variations in copy numbers across different species. Full article