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Frontiers in Genetics 2024The gene plays an essential role in the gametophytic self-incompatibility (GSI) system of . It codes for the stylar-expressed S-RNase protein which inhibits the growth...
The gene plays an essential role in the gametophytic self-incompatibility (GSI) system of . It codes for the stylar-expressed S-RNase protein which inhibits the growth of incompatible pollen tubes through cytotoxicity and the induction of programmed cell death in the pollen tube. While research on the GSI system has primarily focused on the gene, there is still a lack of insight into its spatiotemporal expression profile and the factors that regulate it. Previous studies have suggested that expression in the style is influenced by pollination and is dependent on the compatibility type. We here continue on this basic hypothesis by analyzing the spatiotemporal expression of the alleles in "Conference" styles in response to different types of pollination; namely, upon full- and semi-compatible pollination and upon incompatible selfing. The results revealed that temporal dynamics of expression are influenced by the pollen's compatibility type, indicating the presence of a signaling mechanism between pollen and style to control production during pollen tube growth. In our experiment, expression continuously decreased after cross-pollination and in the unpollinated control. However, after a fully incompatible pollination, expression remained constant. Finally, semi-compatible pollination showed a initially constant expression for both alleles followed by a strong decrease in expression. Based on these results and previous findings, we propose a regulatory mechanism to explain the effect of pollination and the associated compatibility type on expression in the style. This proposed mechanism could be used as a starting point for future research.
PubMed: 38655055
DOI: 10.3389/fgene.2024.1360332 -
Ecology and Evolution Apr 2024In heterostylous plants, short-tongued pollinators are often ineffective/inefficient owing to the limitations imposed by a long corolla tube. However, it is unclear how...
In heterostylous plants, short-tongued pollinators are often ineffective/inefficient owing to the limitations imposed by a long corolla tube. However, it is unclear how disassortative pollen transfer is achieved in small flowers. We investigated the pollination pattern and floral morph variation by analyzing heterostylous syndrome, pollinator groups, and pollen deposition after a single visitation in two populations with short-corolla-tubular small flowers. The predominant pollinators in the Hutubi population were pollen-seeking short-tongued syrphids, which can only transfer pollen between high-level sexual organs. In the Xishan population, nectar-seeking short-tongued insects were efficient pollinators with symmetrical disassortative pollen transfer between high- and low-level sexual organs, whereas long-tongued pollinators had a low efficiency between high-level sexual organs due to the low contact probability with the stigma of long-styled flowers (L-morph), which no longer offered the same advantage observed in tubular flowers. Asymmetrical disassortative pollination may cause the female fitness of short-styled (S-morph) individuals in the Hutubi and L-morph individuals in the Xishan population to suffer greater selection pressure and exhibit a higher degree of floral morph variation. exhibits an unusual pollination pattern in which the small flowers with short corolla tubes make it possible for short-tongued insects to become effective pollinators. However, factors such as the position of stigma-anther within the flower, pollinator species and their preference further caused asymmetrical disassortative pollen transfer. Therefore, more factors should be considered when evaluating the effectiveness of short- and long-tongued insects in pollination service.
PubMed: 38651164
DOI: 10.1002/ece3.11284 -
The Plant Cell Apr 2024Protein S-acylation catalyzed by protein S-acyl transferases (PATs) is a reversible lipid modification regulating protein targeting, stability, and interaction profiles....
Protein S-acylation catalyzed by protein S-acyl transferases (PATs) is a reversible lipid modification regulating protein targeting, stability, and interaction profiles. PATs are encoded by large gene families in plants, and many proteins including receptor-like cytoplasmic kinases (RLCKs) and receptor-like kinases (RLKs) are subject to S-acylation. However, few PATs have been assigned substrates, and few S-acylated proteins have known upstream enzymes. We report that Arabidopsis (Arabidopsis thaliana) class A PATs redundantly mediate pollen tube guidance and participate in the S-acylation of POLLEN RECEPTOR KINASE1 (PRK1) and LOST IN POLLEN TUBE GUIDANCE1 (LIP1), a critical RLK or RLCK for pollen tube guidance, respectively. PAT1, PAT2, PAT3, PAT4, and PAT8, collectively named PENTAPAT for simplicity, are enriched in pollen and show similar subcellular distribution. Functional loss of PENTAPAT reduces seed set due to male gametophytic defects. Specifically, pentapat pollen tubes are compromised in directional growth. We determine that PRK1 and LIP1 interact with PENTAPAT, and their S-acylation is reduced in pentapat pollen. The plasma membrane (PM) association of LIP1 is reduced in pentapat pollen, whereas point mutations reducing PRK1 S-acylation affect its affinity with its interacting proteins. Our results suggest a key role of S-acylation in pollen tube guidance through modulating PM receptor complexes.
PubMed: 38635962
DOI: 10.1093/plcell/koae109 -
Plant Biology (Stuttgart, Germany) Jun 2024Most Aristolochiaceae species studied so far are from temperate regions, bearing self-compatible protogynous trap flowers. Although self-incompatibility has been...
Most Aristolochiaceae species studied so far are from temperate regions, bearing self-compatible protogynous trap flowers. Although self-incompatibility has been suggested for tropical species, the causes of self-sterility in this family remain unknown. To fill this gap, we studied the pollination of the tropical Aristolochia esperanzae, including the physical and physiological anti-selfing mechanisms. Floral visitors trapped inside flowers were collected to determine the pollinators. Protogyny was characterized by observing the temporal expression of sexual phases and stigmatic receptivity tests. The breeding system was investigated using hand-pollination treatments. Pollen tube growth was observed using epifluorescence to identify the self-incompatibility mechanism. Flies were the most frequent visitors found inside A. esperanzae trap flowers, with individuals from the family Ulidiidae being potential pollinators since they carried pollen. The characteristic flower odour and presence of larvae indicate that A. esperanzae deceives flies through oviposition-site mimicry. Although this species showed incomplete protogyny, stigmatic receptivity decreased during the male phase, avoiding self-pollination. Fruits developed only after cross- and open pollination, indicating that the population is non-autonomous, non-apomictic, and self-sterile. This occurred through a delay in the growth of geitonogamous pollen tubes to the ovary and lower ovule penetration, indicating a late-acting self-incompatibility mechanism. Our findings expand the number of families in which late-acting self-incompatibility has been reported, demonstrating that it is more widespread than previously thought, especially when considering less-studied tropical species among the basal angiosperms.
Topics: Pollination; Flowers; Aristolochia; Animals; Self-Incompatibility in Flowering Plants; Pollen Tube; Fruit; Pollen; Diptera
PubMed: 38634401
DOI: 10.1111/plb.13649 -
Plants (Basel, Switzerland) Mar 2024is master regulator of the molecular network involved in pollen tube attraction. Until recently, it was unclear how this gene exhibits exclusively synergid...
is master regulator of the molecular network involved in pollen tube attraction. Until recently, it was unclear how this gene exhibits exclusively synergid cell-specific expression in ovule. Our recent study has established that a 16-bp-long element is crucial for its synergid cell-specific expression in ovule, and an 84-bp-long fragment harboring is sufficient to drive the process. In this study, we have developed a workflow to predict functional roles of potential transcription factors (TFs) putatively binding to the promoter region, taking promoter as a test subject. After sequential assessment of co-expression pattern, network analysis, and potential master regulator identification, we have proposed a multi-TF model for regulation. Our study suggests that ANL2, GT-1, and their respective homologs could be direct regulators of and indicates that TCP15, TCP16, FRS9, and HB34 are likely master regulators of the majority of the TFs involved in its regulation. Comprehensive studies in the future are expected to offer more insights into such propositions. Developed workflow can be used while designing similar regulome-related studies for any other species and genes.
PubMed: 38611536
DOI: 10.3390/plants13071007 -
Plants (Basel, Switzerland) Mar 2024Alfalfa ( L.) is an important forage crop worldwide, but molecular genetics and breeding research in this species are hindered by its self-incompatibility (SI). Although...
Alfalfa ( 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.
PubMed: 38592914
DOI: 10.3390/plants13060875 -
International Journal of Molecular... Mar 2024() genes play key roles in plant root and pollen tube growth, phytohormone responses, and abiotic stress responses. genes in have not yet been explored. Here, genes...
() genes play key roles in plant root and pollen tube growth, phytohormone responses, and abiotic stress responses. genes in have not yet been explored. Here, genes were found to be distributed across eight chromosomes in and were classified into three subfamilies. Promoter sequence analysis of revealed the presence of -elements characteristic of promoters, and these -elements play a role in regulating abiotic stress tolerance and stress-related hormone responses. Organ-specific expression profiling demonstrated that were ubiquitously expressed in all organs, especially the roots, suggesting that they play a role in diverse biological processes. Gene expression analysis revealed that the expression of was significantly up-regulated under osmotic stress and salt stress. RT-qPCR analysis revealed that the expression of was significantly down-regulated under various types of abiotic stress. Protein-protein interaction (PPI) network analysis revealed interactions between RopGEF11, the homolog of , and the VPS34 protein in , as well as interactions between , the homolog of in Arabidopsis, and the ABI1, HAB1, PP2CA, and CPK4 proteins. VPS34, ABI1, HAB1, PP2CA, and CPK4 have previously been shown to confer resistance to unfavorable environments. Overall, our findings suggest that and play significant roles in regulating abiotic stress tolerance. These findings will aid future studies aimed at clarifying the functional characteristics of .
Topics: Brassica rapa; Stress, Physiological; Salt Stress; Multigene Family; Gene Expression Profiling; Phylogeny; Gene Expression Regulation, Plant; Plant Proteins
PubMed: 38542514
DOI: 10.3390/ijms25063541 -
Plant Physiology Jun 2024In flowering plants, male gametes are immotile and carried by dry pollen grains to the female organ. Dehydrated pollen is thought to withstand abiotic stress when grains...
In flowering plants, male gametes are immotile and carried by dry pollen grains to the female organ. Dehydrated pollen is thought to withstand abiotic stress when grains are dispersed from the anther to the pistil, after which sperm cells are delivered via pollen tube growth for fertilization and seed set. Yet, the underlying molecular changes accompanying dehydration and the impact on pollen development are poorly understood. To gain a systems perspective, we analyzed published transcriptomes and proteomes of developing Arabidopsis thaliana pollen. Waves of transcripts are evident as microspores develop to bicellular, tricellular, and mature pollen. Between the "early"- and "late"-pollen-expressed genes, an unrecognized cluster of transcripts accumulated, including those encoding late-embryogenesis abundant (LEA), desiccation-related protein, transporters, lipid-droplet associated proteins, pectin modifiers, cysteine-rich proteins, and mRNA-binding proteins. Results suggest dehydration onset initiates after bicellular pollen is formed. Proteins accumulating in mature pollen like ribosomal proteins, initiation factors, and chaperones are likely components of mRNA-protein condensates resembling "stress" granules. Our analysis has revealed many new transcripts and proteins that accompany dehydration in developing pollen. Together with published functional studies, our results point to multiple processes, including (1) protect developing pollen from hyperosmotic stress, (2) remodel the endomembrane system and walls, (3) maintain energy metabolism, (4) stabilize presynthesized mRNA and proteins in condensates of dry pollen, and (5) equip pollen for compatibility determination at the stigma and for recovery at rehydration. These findings offer novel models and molecular candidates to further determine the mechanistic basis of dehydration and desiccation tolerance in plants.
Topics: Pollen; Arabidopsis; Gene Expression Regulation, Plant; Arabidopsis Proteins; Dehydration; RNA, Messenger; Transcriptome; Gene Expression Profiling
PubMed: 38530638
DOI: 10.1093/plphys/kiae177 -
Frontiers in Plant Science 2024Self-incompatibility (SI) is a genetic mechanism common in flowering plants to prevent self-fertilization. Among citrus species, several pummelo, mandarin, and...
Self-incompatibility (SI) is a genetic mechanism common in flowering plants to prevent self-fertilization. Among citrus species, several pummelo, mandarin, and mandarin-like accessions show SI behavior. In these species, SI is coupled with a variable degree of parthenocarpy ensuring the production of seedless fruits, a trait that is highly appreciated by consumers. In , recent evidences have shown the presence of a gametophytic SI system based on () ability to impair self-pollen tube growth in the upper/middle part of the style. In the present study, we combined PCR analysis and next-generation sequencing technologies, to define the presence of and in the -genotype of the (Hort. ex Tan.), the self-incompatible 'Comune' clementine and its self-compatible natural mutant 'Monreal'. The reference genome of 'Monreal' clementine is presented for the first time, providing more robust results on the genetic sequence of the newly discovered SNP discovery analysis coupled with the annotation of the variants detected enabled the identification of 7,781 SNPs effecting 5,661 genes in 'Monreal' compared to the reference genome of . Transcriptome analysis of unpollinated pistils at the mature stage from both clementine genotypes revealed the lack of expression of in 'Monreal' suggesting its involvement in the loss of the SI response. RNA-seq analysis followed by gene ontology studies enabled the identification of 2,680 differentially expressed genes (DEGs), a significant number of those is involved in oxidoreductase and transmembrane transport activity. Merging of DNA sequencing and RNA data led to the identification of 164 DEGs characterized by the presence of at least one SNP predicted to induce mutations with a high effect on their amino acid sequence. Among them, four candidate genes referring to two -like MADS-box proteins, to and to -like protein 12 were validated. Moreover, the transcription factor appeared to contain a binding site for the 2.0-kb upstream sequences of the and genes. These results provide useful information about the genetic bases of SI indicating that SNPs present in their sequence could be responsible for the differential expression and the regulation of and consequently of the SI mechanism.
PubMed: 38501136
DOI: 10.3389/fpls.2024.1360087 -
Plant Physiology and Biochemistry : PPB Mar 2024In staple crops, such as rice (Oryza sativa L.), pollen plays a crucial role in seed production. However, the molecular mechanisms underlying rice pollen germination and...
In staple crops, such as rice (Oryza sativa L.), pollen plays a crucial role in seed production. However, the molecular mechanisms underlying rice pollen germination and tube growth remain underexplored. Notably, we recently uncovered the redundant expression and mutual interaction of two rice genes encoding cyclic nucleotide-gated channels (CNGCs), OsCNGC4 and OsCNGC5, in mature pollen. Building on these findings, the current study focused on clarifying the functional roles of these two genes in pollen germination and tube growth. To overcome functional redundancy, we produced gene-edited rice plants with mutations in both genes using the CRISPR-Cas9 system. The resulting homozygous OsCNGC4 and OsCNGC5 gene-edited mutants (oscngc4/5) exhibited significantly lower pollen germination rates than the wild type (WT), along with severely reduced fertility. Transcriptome analysis of the double oscngc4/5 mutant revealed downregulation of genes related to receptor kinases, transporters, and cell wall metabolism. To identify the direct regulators of OsCNGC4, which form a heterodimer with OsCNGC5, we screened a yeast two-hybrid library containing rice cDNAs from mature anthers. Subsequently, we identified two calmodulin isoforms (CaM1-1 and CaM1-2), NETWORKED 2 A (NET2A), and proline-rich extension-like receptor kinase 13 (PERK13) proteins as interactors of OsCNGC4, suggesting its roles in regulating Ca channel activity and F-actin organization. Overall, our results suggest that OsCNGC4 and OsCNGC5 may play critical roles in pollen germination and elongation by regulating the Ca gradient in growing pollen tubes.
Topics: Oryza; Cyclic Nucleotide-Gated Cation Channels; Germination; Pollen; Pollen Tube; Calmodulin; Phosphotransferases; Nucleotides, Cyclic
PubMed: 38493663
DOI: 10.1016/j.plaphy.2024.108522