Search Results (49)

Visual odometry (VO), including keypoint detection, correspondence establishment, and pose estimation, is a crucial technique for determining motion in machine vision, with significant applications in augmented reality (AR), autonomous driving, and visual simultaneous localization and mapping (SLAM). For feature-based VO, the repeatability of keypoints affects the pose estimation. The convolutional neural network (CNN)-based detectors extract high-level features from images, thereby exhibiting robustness to viewpoint and illumination changes. Compared with descriptor matching, optical flow tracking exhibits better real-time performance. However, mainstream CNN-based detectors rely on the “joint detection and descriptor” framework to realize matching, making them incompatible with optical flow tracking. To obtain keypoints suitable for optical flow tracking, we propose a self-supervised detector based on transfer learning named OFPoint, which jointly calculates pixel-level positions and confidences. We use the descriptor-based detector simple learned keypoints (SiLK) as the pre-trained model and fine-tune it to avoid training from scratch. To achieve multi-scale feature fusion in detection, we integrate the multi-scale attention mechanism. Furthermore, we introduce the maximum discriminative probability loss term, ensuring the grayscale consistency and local stability of keypoints. OFPoint achieves a balance between accuracy and real-time performance when establishing correspondences on HPatches. Additionally, we demonstrate its effectiveness in VO and its potential for graphics applications such as AR. Full article

The potential role of reactive oxygen species (ROS) is studied in the male gametophytes of petunia (Petunia hybrida E. Vilm.) grown in vivo with a focus on its germination, growth support in the progamic stage of fertilization, and the function of the mechanism underlying S-RNase-based self-incompatibility. Exogenous treatment with H₂O₂ influences the in vivo germination and polar growth of pollen tubes (PTs), which manifests as the acceleration or inhibition of these processes depending on its concentration, time interval after pollination, and pollination variant. The H₂O₂ treatment of the stigma somewhat stimulates the PT elongation in the late stages of self-incompatible pollination (4–8 h) versus the strong PT inhibition observed during the first hour of germination. A different pattern is observable in cross-compatible pollination: the H₂O₂ treatment of pistils inhibits PT growth during the overall pollination at all tested concentrations. Treatment of pistils with the NADPH oxidase inhibitor diphenylene iodonium chloride (DPI) strongly inhibited the growth of PTs in both pollination variants. In addition, DCF-DA staining confirms that ROS are formed in pollen, PTs, stigma of nonpollinated pistil, and the pistil itself in all pollination variants. The PT growth during the function of the self-incompatibility mechanism is arrested at high ROS concentrations, which is presumably associated with the SI-induced programmed cell death. Our results demonstrate that ROS are a necessary component of pollen, PTs, exudate, and stigma cells and contribute to successful reproduction. This study provides a deeper insight into the ROS functions during the PT growth in an in vivo system. Full article

Self-incompatibility (SI) is a complex mechanism that prevents plants from self-fertilizing to preserve and promote genetic variability. The angiosperm species have developed two different SI systems, the sporophytic (SSI) and the gametophytic (GSI) systems. SI is a significant impediment to steady fruit production in fruit tree species of the Rosaceae. In Rosaceae, GSI is genetically regulated via a single locus, named the ‘S-locus’, which includes a minimum of two polymorphic and relatively intercorrelated S genes: a pistil-expressed S-RNase gene and several pollen-expressed SFBB (S-locus F-Box Brothers) or SFB (S haplotype-specific F-box protein). This necessitates the interaction of S-RNases with the male determinants. Although genetic and molecular analyses of S genes have shown that mutations in both pistils and pollen-specific components induce self-compatibility in many species and cultivars, other genes or molecules outside the S-locus can co-participate in the male gamete rejection in GSI. However, we highlight and synthesize the most recent knowledge on different mechanisms of GSI in Rosaceae in this current review. Full article

Self-incompatibility (SI) poses a significant reproductive barrier, severely impacting the yield, quality, and economic value of Camellia oleifera. In this study, methyl jasmonate (MeJA) was employed as an exogenous stimulus to alleviate SI in C. oleifera. The research findings revealed that an exogenous dose of 1000 μmol·L⁻¹ MeJA enhanced the germination and tube growth of C. oleifera self-pollen and greatly improved ovule penetration (18.75%) and fertilization (15.81%), ultimately increasing fruit setting (18.67%). It was discovered by transcriptome analysis that the key genes (CAD, C4H) involved in the lignin production process exhibited elevated expression levels in self-pistils treated with MeJA. Further analysis showed that the lignin concentration in the MeJA-treated pistils was 31.70% higher compared with the control group. As verified by pollen germination assays in vitro, lignin in the appropriate concentration range could promote pollen tube growth. Gene expression network analysis indicated that transcription factor bHLH may be pivotal in regulating lignin biosynthesis in response to MeJA, which in turn affects pollen tubes. Further transient knockdown of bHLH (Co_33962) confirmed its important role in C. oleifera pollen tube growth. In summary, the application of MeJA resulted in the stimulation of self-pollen tube elongation and enhanced fruit setting in C. oleifera, which could be associated with the differential change in genes related to lignin synthesis and the increased lignin content. Full article

Self-incompatibility (SI) systems in plants prevent self-pollination and mating among relatives, enhancing genetic diversity in nature but posing challenges in almond production and breeding. S-allele composition alongside the flowering periods of these cultivars enables the anticipation of cross-compatibility and optimal cultivar combinations for the allocation of pollinating trees in production. In the current study, 65 materials containing 61 almond (Prunus dulcis) germplasm resources, of which two were hybrids and the remaining four were peach (Prunus persica) germplasms, were used for the S-RNase genotype. The results showed that 55 genomic samples were amplified by PCR to obtain double-banded types, which identified their complete S-RNase genotypes, while the rest of the samples amplified only a single band, identifying one S-RNase gene in the S gene. A total of 30 S-RNase genes were identified in Prunus dulcis, Prunus webbii, Prunus persica, Prunus armeniaca, Prunus salicina, and Prunus cerasifera. Sequence analysis revealed polymorphisms spanning from 313 to 2031 bp within the amplified fragment sequence. The S₅₇-RNase gene exhibited the highest frequency at 31.75% among the identified materials, with S₁S₅₇, S₁₀S₅₇, and S₇S₅₇ being the predominant S genotypes. A new S-RNase gene, named S₆₅, was identified with a sequencing length of 1483 bp. Its deduced amino acid sequence shared 98.24% similarity with the amino acid sequence of the S-RNase gene on GenBank, with the highest homology. Furthermore, according to the findings, 65 materials belong to eight S genotype cross-incompatibility groups (CIG) and one semi-compatibility or compatibility group (0). Among them, most of the seven main almond germplasm resources and 35 cultivars can be cross-pollinated. The results of the study can lay the foundation for pollinator tree allocation and breeding hybrid parent selection in almond production. Full article

Alfalfa (Medicago sativa L.) is an important forage crop worldwide, but molecular genetics and breeding research in this species are hindered by its self-incompatibility (SI). Although the mechanisms underlying SI have been extensively studied in other plant families, SI in legumes, including alfalfa, remains poorly understood. Here, we determined that self-pollinated pollen tubes could germinate on the stigma of alfalfa, grow through the style, and reach the ovarian cavity, but the ovules collapsed ~48 h after self-pollination. A transcriptomic analysis of dissected pistils 24 h after self-pollination identified 941 differently expressed genes (DEGs), including 784 upregulated and 157 downregulated genes. A gene ontology (GO) analysis showed that the DEGs were highly enriched in functions associated with the regulation of pollen tube growth and pollen germination. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that pentose and glucuronate interconversion, plant hormone signal transduction, the spliceosome, and ribosomes might play important roles in SI. Our co-expression analysis showed that F-box proteins, serine/threonine protein kinases, calcium-dependent protein kinases (CDPKs), bHLHs, bZIPs, and MYB-related family proteins were likely involved in the SI response. Our study provides a catalog of candidate genes for further study to understand SI in alfalfa and related legumes. Full article

Acacia mangium is well known as a valuable commercial tree species in the Acacia genus. A. mangium was recently found to be self-incompatible (SI), but its SI mechanism is not clear, which has hindered the progress of genetic improvement of A. mangium with strong resistance. To confirm the SI type of A. mangium, pollen germination was observed via fluorescence microscopy at 0 h, 3 h, 6 h, 9 h, 12 h, and 24 h after self-pollination. We found over ninety percent of the pollen grains produced no pollen tube growth on the stigma/style. To further explore the SI molecular mechanism of A. mangium, tests of the transcriptome and metabolome were carried out after self-pollination. Observations of pollen germination after self-pollination using fluorescence microscopy suggested that the SI type of A. mangium is gametophytic self-incompatibility (GSI). A combined transcriptomic and metabolomic analysis showed that DEGs (differentially expressed genes) related to SI (6 S-glycoproteins, 93 F-box proteins, 69 26S proteasomes, 38 calcium-dependent protein kinases/calmodulin and 41 thioredoxin genes) were significantly enriched in six KEGG (sulfur metabolism, tyrosine metabolism, phenylalanine metabolism, butanoate metabolism, and valine, leucine, and isoleucine degradation). Further analysis of these six pathways revealed the enrichment of SI-related DEGs corresponding to succinate, methylmalonate, and 3-hydroxypropane. These three metabolites were significantly downregulated. The analysis of transcripts and metabolites suggested that transcripts of SI-related gene families (thioredoxin and F-box protein) were significantly upregulated under the regulation of transcription factors (TFs) after self-pollination, leading to a decrease in metabolites (such as succinate, methylmalonate, and 3-hydroxypropionate). We also further speculated that TFs (MYB, HB-HD-ZIP, AP2/ERF-ERF, and bZIP) and gene families (thioredoxin and F-box protein) were important factors related to the SI of A. mangium. Full article

Self-incompatible pitaya varieties have low fruit-setting rates under natural conditions, leading to higher production costs and hindering industrial prosperity. Through transcriptome sequencing, we obtained the 36,900 longest transcripts (including 9167 new transcripts) from 60 samples of flowers. Samples were collected pre- and post-pollination (at 0 h, 0.5 h, 2 h, 4 h, and 12 h) from two varieties of pitaya (self-compatible Jindu No. 1 and self-incompatible Cu Sha). Using the RNA-Seq data and comparison of reference genomes, we annotated 28,817 genes in various databases, and 1740 genes were optimized in their structure for annotation. There were significant differences in the expression of differentially expressed genes (DEGs) in the pitaya stigmas under different pollination types, especially at the late post-pollination stage, where the expression of protease genes increasedal significantly under cross-pollination. We identified DEGs involved in the ribosomal, ubiquitination-mediated, and phyto-signaling pathways that may be involved in pitaya SI regulation. Based on the available transcriptome data and bioinformatics analysis, we tentatively identified HuS-RNase2 as a candidate gynogenetic S gene in the pitaya GSI system. Full article

Research into molecular mechanisms of self-incompatibility (SI) in plants can be observed in representatives of various families, including Solanaceae. Earlier studies of the mechanisms of S-RNase-based SI in petunia (Petunia hybrida E. Vilm.) demonstrate that programmed cell death (PCD) is an SI factor. These studies suggest that the phytohormon cytokinin (CK) is putative activator of caspase-like proteases (CLPs). In this work, data confirming this hypothesis were obtained in two model objects—petunia and tomato (six Solanaceae representatives). The exogenous zeatin treatment of tomato and petunia stigmas before a compatible pollination activates CLPs in the pollen tubes in vivo, as shown via the intravital imaging of CLP activities. CK at any concentration slows down the germination and growth of petunia and tomato male gametophytes both in vitro and in vivo; shifts the pH of the cytoplasm (PHc) to the acid region, thereby creating the optimal conditions for CLP to function and inhibiting the F-actin formation and/or destructing the cytoskeleton in pollen tubes to point foci during SI-induced PCD; and accumulates in style tissues during SI response. The activity of the ISOPENTENYLTRANSFERASE 5 (IPT5) gene at this moment exceeds its activity in a cross-compatible pollination, and the levels of expression of the CKX1 and CKX2 genes (CK OXIDASE/DEHYDROGENASE) are significantly lower in self-incompatible pollination. All this suggests that CK plays a decisive role in the mechanism underlying SI-induced PCD. Full article

To address the complex challenges faced by our planet such as rapidly changing climate patterns, food and nutritional insecurities, and the escalating world population, the development of hybrid vegetable crops is imperative. Vegetable hybrids could effectively mitigate the above-mentioned fundamental challenges in numerous countries. Utilizing genetic mechanisms to create hybrids not only reduces costs but also holds significant practical implications, particularly in streamlining hybrid seed production. These mechanisms encompass self-incompatibility (SI), male sterility, and gynoecism. The present comprehensive review is primarily focused on the elucidation of fundamental processes associated with floral characteristics, the genetic regulation of floral traits, pollen biology, and development. Specific attention is given to the mechanisms for masculinizing and feminizing cucurbits to facilitate hybrid seed production as well as the hybridization approaches used in the biofortification of vegetable crops. Furthermore, this review provides valuable insights into recent biotechnological advancements and their future utilization for developing the genetic systems of major vegetable crops. Full article

The Camellia oil tree (Camellia oleifera Abel.) is an important nonwood forest species in China, and the majority of its cultivars are late-acting self-incompatibility (LSI) types. Although several studies have examined the mechanism of LSI, the process is quite complicated and unclear. In this study, pollen tube growth and fruit setting of two Camellia oil tree cultivars Huashuo (HS) and Huajin (HJ) were investigated after non and self-pollination, and transcriptomic analysis of the ovaries was performed 48 h after self-pollination to identify the potential genes implicated in the LSI of Camellia oil trees. The results showed that the fruit set of HS was significantly higher than that of HJ after self-pollination. Transcriptomic analysis revealed that plant hormone signal transduction, the phosphatidylinositol signaling system, ATP-binding cassette (ABC) transporters, reactive oxygen species (ROS) metabolism, and Ca²⁺ signaling were mainly contributed in the LSI of reaction of Camellia oil tree. Moreover, nine RNase T2 genes were identified from the transcriptome analysis, which also showed that CoRNase7 participated in the self-incompatibility reaction in HS. Based on phylogenetic analysis, CoRNase6 was closely related to S-RNase from coffee, and CoRNase7 and CoRNase8 were closely related to S-RNase from Camellia sinensis. The 9 RNase T2 genes successfully produced proteins in prokaryotes. Subcellular localization indicated that CoRNase1 and CoRNase5 were cytoplasmic proteins, while CoRNase7 was a plasma membrane protein. These results screened the main metabolic pathways closely related to LSI in Camellia oil tree, and SI signal transduction might be regulated by a large molecular regulatory network. The discovery of T2 RNases provided evidence that Camellia oil tree might be under RNase-based gametophytic self-incompatibility. Full article

Heavy metal-associated proteins (HMPs) participate in heavy metal detoxification. Although HMPs have been identified in several plants, no studies to date have identified the HMPs in Brassica rapa (B. rapa). Here, we identified 85 potential HMPs in B. rapa by bioinformatic methods. The promoters of the identified genes contain many elements associated with stress responses, including response to abscisic acid, low-temperature, and methyl jasmonate. The expression levels of BrHMP14, BrHMP16, BrHMP32, BrHMP41, and BrHMP42 were upregulated under Cu²⁺, Cd²⁺, Zn²⁺, and Pb²⁺ stresses. BrHMP06, BrHMP30, and BrHMP41 were also significantly upregulated after drought treatment. The transcripts of BrHMP06 and BrHMP11 increased mostly under cold stress. After applying salt stress, the expression of BrHMP02, BrHMP16, and BrHMP78 was induced. We observed increased BrHMP36 expression during the self-incompatibility (SI) response and decreased expression in the compatible pollination (CP) response during pollen–stigma interactions. These changes in expression suggest functions for these genes in HMPs include participating in heavy metal transport, detoxification, and response to abiotic stresses, with the potential for functions in sexual reproduction. We found potential co-functional partners of these key players by protein–protein interaction (PPI) analysis and found that some of the predicted protein partners are known to be involved in corresponding stress responses. Finally, phosphorylation investigation revealed many phosphorylation sites in BrHMPs, suggesting post-translational modification may occur during the BrHMP-mediated stress response. This comprehensive analysis provides important clues for the study of the molecular mechanisms of BrHMP genes in B. rapa, especially for abiotic stress and pollen–stigma interactions. Full article

Brassica vegetables are very important to human beings. Self-incompatibility (SI) is a common phenomenon in Brassica. Breeding by SI lines is an important way to utilize heterosis of Brassica vegetables. It is believed that the SI inheritance in Brassica species is controlled by three linkage genes on the S-locus, including SRK (S-locus receptor kinase), SCR (S-locus cystine-rich protein)/SP11 (S-locus protein 11), and SLG (S-locus glycoprotein). SRK is the female determinant and SCR/SP11 is the pollen S gene. The expression of SLG is necessary for SRK, and it enhances the SRK-mediated SI reaction. In addition to these three S-locus genes, some other functional molecules also have significant regulatory effects on SI, such as ARC1 (arm repeat containing 1), MLPK (M-locus protein kinase), Exo70A1 (exocyst compounds), THLl/THL2 (thioredoxin H-like), MOD (aquaporin), SLR (S-locus-related glycoprotein), BPCI (pollen calcium-binding protein I), etc. SI is also associated with the dominant/recessive relationship between S alleles. Here, the genetic elements and molecular mechanisms of SI, mainly in Brassica vegetables, are reviewed. Full article

In Brassicaceae, the papillary cells of the stigma are the primary site of the self-incompatibility (SI) responses. SI preserves the genetic diversity by selectively rejecting irrelevant or incompatible pollen, thus promoting cross fertilization and species fitness. Mechanisms that regulate SI responses in Brassica have been studied mainly on the mature stigma that often undermines how stigma papillary cells attain the state of SI during development. To understand this, we integrated PacBio SMRT-seq with Illumina RNA-seq to construct a de novo full-length transcriptomic database for different stages of stigma development in ornamental kale. A total of 48,800 non-redundant transcripts, 31,269 novel transcripts, 24,015 genes, 13,390 alternative splicing, 22,389 simple sequence repeats, 21,816 complete ORF sequences, and 4591 lncRNAs were identified and analyzed using PacBio SMRT-seq. The Illumina RNA-seq revealed 15,712 differentially expressed genes (DEGs) and 8619 transcription factors. The KEGG enrichment analysis of 4038 DEGs in the “incompatibility” group revealed that the flavonoid and fatty acid biosynthesis pathways were significantly enriched. The cluster and qRT-PCR analysis indicated that 11 and 14 candidate genes for the flavonoid and fatty acid biosynthesis pathways have the lowest expression levels at stigma maturation, respectively. To understand the physiological relevance of the downregulation of fatty acid biosynthesis pathways, we performed inhibitor feeding assays on the mature stigma. The compatible pollination response was drastically reduced when mature stigmas were pre-treated with a fatty acid synthase inhibitor. This finding suggested that fatty acid accumulation in the stigmas may be essential for compatible pollination and its downregulation during maturity must have evolved as a support module to discourage the mounting of self-incompatible pollen. Full article

S-RNase plays vital roles in the process of self-incompatibility (SI) in Rutaceae plants. Data have shown that the rejection phenomenon during self-pollination is due to the degradation of pollen tube RNA by S-RNase. The cytoskeleton microfilaments of pollen tubes are destroyed, and other components cannot extend downwards from the stigma and, ultimately, cannot reach the ovary to complete fertilisation. In this study, four S-RNase gene sequences were identified from the ‘XiangShui’ lemon genome and ubiquitome. Sequence analysis revealed that the conserved RNase T2 domains within S-RNases in ‘XiangShui’ lemon are the same as those within other species. Expression pattern analysis revealed that S₃-RNase and S₄-RNase are specifically expressed in the pistils, and spatiotemporal expression analysis showed that the S₃-RNase expression levels in the stigmas, styles and ovaries were significantly higher after self-pollination than after cross-pollination. Subcellular localisation analysis showed that the S₁-RNase, S₂-RNase, S₃-RNase and S₄-RNase were found to be expressed in the nucleus according to laser confocal microscopy. In addition, yeast two-hybrid (Y2H) assays showed that S₃-RNase interacted with F-box, Bifunctional fucokinase/fucose pyrophosphorylase (FKGP), aspartic proteinase A1, RRP46, pectinesterase/pectinesterase inhibitor 51 (PME51), phospholipid:diacylglycerol acyltransferase 1 (PDAT1), gibberellin receptor GID1B, GDT1-like protein 4, putative invertase inhibitor, tRNA ligase, PAP15, PAE8, TIM14-2, PGIP1 and p24beta2. Moreover, S₃-RNase interacted with TOPP4. Therefore, S₃-RNase may play an important role in the SI of ‘XiangShui’ lemon. Full article