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Zhang W, Zhang Q, Xing Y, Cao Q, Qin L, Fang K. Effect of boron toxicity on pollen tube cell wall architecture and the relationship of cell wall components of Castanea mollissima Blume. FRONTIERS IN PLANT SCIENCE 2022; 13:946781. [PMID: 35958218 PMCID: PMC9361862 DOI: 10.3389/fpls.2022.946781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 07/04/2022] [Indexed: 06/15/2023]
Abstract
Boron (B) is essential to plant development. However, excessive B is toxic to plants. This research was performed to evaluate the effects of B toxicity on cell wall architecture of Chinese chestnut (Castanea mollissima Blume) pollen tubes with emphasis on the relationship among pectins, cellulose, and callose. Results showed that 0.8 mM H3BO3 inhibited pollen germination and led to abnormal morphology of the pollen tubes. B toxicity also affected the distribution of cell wall components of the pollen tube. In control pollen tube, esterified and acid pectins were distributed unevenly, with the former mainly at the tip and the latter on the distal region. Cellulose was distributed uniformly on the surface with less at the tip; callose reduced gradually from base to sub-tip of the pollen tubes and no callose at the tip of the tube was detected. B toxicity led to the deposition of esterified and acid pectins, cellulose, and callose at the tip of the pollen tube. Results from scanning electron microscopy and transmission electron microscopy showed that B toxicity also altered pollen tube wall ultrastructure. The results from enzymatic treatment illustrated that there existed a close relationship among pectins, cellulose, and callose. B toxicity also altered the relationship. In a word, B toxicity altered deposition and relationship of pectins, cellulose, and callose of pollen tube wall.
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Cai G. The legacy of kinesins in the pollen tube thirty years later. Cytoskeleton (Hoboken) 2022; 79:8-19. [PMID: 35766009 PMCID: PMC9542081 DOI: 10.1002/cm.21713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 06/06/2022] [Accepted: 06/27/2022] [Indexed: 11/10/2022]
Abstract
The pollen tube is fundamental in the reproduction of seed plants. Particularly in angiosperms, we now have much information about how it grows, how it senses extracellular signals, and how it converts them into a directional growth mechanism. The expansion of the pollen tube is also related to dynamic cytoplasmic processes based on the cytoskeleton (such as polymerization/depolymerization of microtubules and actin filaments) or motor activity along with the two cytoskeletal systems and is dependent on motor proteins. While a considerable amount of information is available for the actomyosin system in the pollen tube, the role of microtubules in the transport of organelles or macromolecular structures is still quite uncertain despite that 30 years ago the first work on the presence of kinesins in the pollen tube was published. Since then, progress has been made in elucidating the role of kinesins in plant cells. However, their role within the pollen tube is still enigmatic. In this review, I will postulate some roles of kinesins in the pollen tube 30 years after their initial discovery based on information obtained in other plant cells in the meantime. The most concrete hypotheses predict that kinesins in the pollen tube enable the short movement of specific organelles or contribute to generative cell or sperm cell transport, as well as mediate specific steps in the process of endocytosis.
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Lara-Mondragón CM, Dorchak A, MacAlister CA. O-glycosylation of the extracellular domain of pollen class I formins modulates their plasma membrane mobility. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:3929-3945. [PMID: 35383367 PMCID: PMC9232206 DOI: 10.1093/jxb/erac131] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 03/31/2022] [Indexed: 06/09/2023]
Abstract
In plant cells, linkage between the cytoskeleton, plasma membrane, and cell wall is crucial for maintaining cell shape. In highly polarized pollen tubes, this coordination is especially important to allow rapid tip growth and successful fertilization. Class I formins contain cytoplasmic actin-nucleating formin homology domains as well as a proline-rich extracellular domain and are candidate coordination factors. Here, using Arabidopsis, we investigated the functional significance of the extracellular domain of two pollen-expressed class I formins: AtFH3, which does not have a polar localization, and AtFH5, which is limited to the growing tip region. We show that the extracellular domain of both is necessary for their function, and identify distinct O-glycans attached to these sequences, AtFH5 being hydroxyproline-arabinosylated and AtFH3 carrying arabinogalactan chains. Loss of hydroxyproline arabinosylation altered the plasma membrane localization of AtFH5 and disrupted actin cytoskeleton organization. Moreover, we show that O-glycans differentially affect lateral mobility in the plasma membrane. Together, our results support a model of protein sub-functionalization in which AtFH5 and AtFH3, restricted to specific plasma membrane domains by their extracellular domains and the glycans attached to them, organize distinct subarrays of actin during pollen tube elongation.
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Kaur D, Moreira D, Coimbra S, Showalter AM. Hydroxyproline- O-Galactosyltransferases Synthesizing Type II Arabinogalactans Are Essential for Male Gametophytic Development in Arabidopsis. FRONTIERS IN PLANT SCIENCE 2022; 13:935413. [PMID: 35774810 PMCID: PMC9237623 DOI: 10.3389/fpls.2022.935413] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 05/17/2022] [Indexed: 05/25/2023]
Abstract
In flowering plants, male reproductive function is determined by successful development and performance of stamens, pollen grains, and pollen tubes. Despite the crucial role of highly glycosylated arabinogalactan-proteins (AGPs) in male gamete formation, pollen grain, and pollen tube cell walls, the underlying mechanisms defining these functions of AGPs have remained elusive. Eight partially redundant Hyp-galactosyltransferases (named GALT2-GALT9) genes/enzymes are known to initiate Hyp-O-galactosylation for Hyp-arabinogalactan (AG) production in Arabidopsis thaliana. To assess the contributions of these Hyp-AGs to male reproductive function, we used a galt2galt5galt7galt8galt9 quintuple Hyp-GALT mutant for this study. Both anther size and pollen viability were compromised in the quintuple mutants. Defects in male gametogenesis were observed in later stages of maturing microspores after meiosis, accompanied by membrane blebbing and numerous lytic vacuoles. Cytological and ultramicroscopic observations revealed that pollen exine reticulate architecture and intine layer development were affected such that non-viable collapsed mature pollen grains were produced, which were devoid of cell content and nuclei, with virtually no intine. AGP immunolabeling demonstrated alterations in cell wall architecture of the anther, pollen grains, and pollen tube. Specifically, the LM2 monoclonal antibody (which recognized β-GlcA epitopes on AGPs) showed a weak signal for the endothecium, microspores, and pollen tube apex. Pollen tube tips also displayed excessive callose deposition. Interestingly, expression patterns of pollen-specific AGPs, namely AGP6, AGP11, AGP23, and AGP40, were determined to be higher in the quintuple mutants. Taken together, our data illustrate the importance of type-II AGs in male reproductive function for successful fertilization.
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Ropitaux M, Hays Q, Baron A, Fourmois L, Boulogne I, Vauzeilles B, Lerouge P, Mollet JC, Lehner A. Dynamic imaging of cell wall polysaccharides by metabolic click-mediated labeling of pectins in living elongating cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:916-924. [PMID: 35165972 DOI: 10.1111/tpj.15706] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
Protein tracking in living plant cells has become routine with the emergence of reporter genes encoding fluorescent tags. Unfortunately, this imaging strategy is not applicable to glycans because they are not directly encoded by the genome. Indeed, complex glycans result from sequential additions and/or removals of monosaccharides by the glycosyltransferases and glycosidases of the cell's biosynthetic machinery. Currently, the imaging of cell wall polymers mainly relies on the use of antibodies or dyes that exhibit variable specificities. However, as immunolocalization typically requires sample fixation, it does not provide access to the dynamics of living cells. The development of click chemistry in plant cell wall biology offers an alternative for live-cell labeling. It consists of the incorporation of a carbohydrate containing a bio-orthogonal chemical reporter into the target polysaccharide using the endogenous biosynthetic machinery of the cell. Once synthesized and deposited in the cell wall, the polysaccharide containing the analog monosaccharide is covalently coupled to an exogenous fluorescent probe. Here, we developed a metabolic click labeling approach which allows the imaging of cell wall polysaccharides in living and elongating cells without affecting cell viability. The protocol was established using the pollen tube, a useful model to follow cell wall dynamics due to its fast and tip-polarized growth, but was also successfully tested on Arabidopsis root cells and root hairs. This method offers the possibility of imaging metabolically incorporated sugars of viable and elongating cells, allowing the study of the long-term dynamics of labeled extracellular polysaccharides.
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Jiang Y, Lu Q, Huang S. Functional non-equivalence of pollen ADF isovariants in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:1068-1081. [PMID: 35233873 DOI: 10.1111/tpj.15723] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 02/24/2022] [Accepted: 02/26/2022] [Indexed: 06/14/2023]
Abstract
ADF/cofilin is a central regulator of actin dynamics. We previously demonstrated that two closely related Arabidopsis class IIa ADF isovariants, ADF7 and ADF10, are involved in the enhancement of actin turnover in pollen, but whether they have distinct functions remains unknown. Here, we further demonstrate that they exhibit distinct functions in regulating actin turnover both in vitro and in vivo. We found that ADF7 binds to ADP-G-actin with lower affinity, and severs and depolymerizes actin filaments less efficiently in vitro than ADF10. Accordingly, in pollen grains, ADF7 more extensively decorates actin filaments and is less freely distributed in the cytoplasm compared to ADF10. We further demonstrate that ADF7 and ADF10 show distinct intracellular localizations during pollen germination, and they have non-equivalent functions in promoting actin turnover in pollen. We thus propose that cooperation and labor division of ADF7 and ADF10 enable pollen cells to achieve exquisite control of the turnover of different actin structures to meet different cellular needs.
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Scholz P, Pejchar P, Fernkorn M, Škrabálková E, Pleskot R, Blersch K, Munnik T, Potocký M, Ischebeck T. DIACYLGLYCEROL KINASE 5 regulates polar tip growth of tobacco pollen tubes. THE NEW PHYTOLOGIST 2022; 233:2185-2202. [PMID: 34931304 DOI: 10.1111/nph.17930] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 12/06/2021] [Indexed: 06/14/2023]
Abstract
Pollen tubes require a tightly regulated pectin secretion machinery to sustain the cell wall plasticity required for polar tip growth. Involved in this regulation at the apical plasma membrane are proteins and signaling molecules, including phosphoinositides and phosphatidic acid (PA). However, the contribution of diacylglycerol kinases (DGKs) is not clear. We transiently expressed tobacco DGKs in pollen tubes to identify a plasma membrane (PM)-localized isoform, and then to study its effect on pollen tube growth, pectin secretion and lipid signaling. In order to potentially downregulate DGK5 function, we overexpressed an inactive variant. Only one of eight DGKs displayed a confined localization at the apical PM. We could demonstrate its enzymatic activity and that a kinase-dead variant was inactive. Overexpression of either variant led to differential perturbations including misregulation of pectin secretion. One mode of regulation could be that DGK5-formed PA regulates phosphatidylinositol 4-phosphate 5-kinases, as overexpression of the inactive DGK5 variant not only led to a reduction of PA but also of phosphatidylinositol 4,5-bisphosphate levels and suppressed related growth phenotypes. We conclude that DGK5 is an additional player of polar tip growth that regulates pectin secretion probably in a common pathway with PI4P 5-kinases.
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Kaashyap M, Ford R, Mann A, Varshney RK, Siddique KHM, Mantri N. Comparative Flower Transcriptome Network Analysis Reveals DEGs Involved in Chickpea Reproductive Success during Salinity. PLANTS (BASEL, SWITZERLAND) 2022; 11:434. [PMID: 35161414 PMCID: PMC8838858 DOI: 10.3390/plants11030434] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 02/03/2022] [Accepted: 02/03/2022] [Indexed: 05/27/2023]
Abstract
Salinity is increasingly becoming a significant problem for the most important yet intrinsically salt-sensitive grain legume chickpea. Chickpea is extremely sensitive to salinity during the reproductive phase. Therefore, it is essential to understand the molecular mechanisms by comparing the transcriptomic dynamics between the two contrasting genotypes in response to salt stress. Chickpea exhibits considerable genetic variation amongst improved cultivars, which show better yields in saline conditions but still need to be enhanced for sustainable crop production. Based on previous extensive multi-location physiological screening, two identified genotypes, JG11 (salt-tolerant) and ICCV2 (salt-sensitive), were subjected to salt stress to evaluate their phenological and transcriptional responses. RNA-Sequencing is a revolutionary tool that allows for comprehensive transcriptome profiling to identify genes and alleles associated with stress tolerance and sensitivity. After the first flowering, the whole flower from stress-tolerant and sensitive genotypes was collected. A total of ~300 million RNA-Seq reads were sequenced, resulting in 2022 differentially expressed genes (DEGs) in response to salt stress. Genes involved in flowering time such as FLOWERING LOCUS T (FT) and pollen development such as ABORTED MICROSPORES (AMS), rho-GTPase, and pollen-receptor kinase were significantly differentially regulated, suggesting their role in salt tolerance. In addition to this, we identify a suite of essential genes such as MYB proteins, MADS-box, and chloride ion channel genes, which are crucial regulators of transcriptional responses to salinity tolerance. The gene set enrichment analysis and functional annotation of these genes in flower development suggest that they can be potential candidates for chickpea crop improvement for salt tolerance.
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Zhang MJ, Zhao TY, Ouyang XK, Zhao XY, Dai X, Gao XQ. Pollen-specific gene SKU5-SIMILAR 13 enhances growth of pollen tubes in the transmitting tract in Arabidopsis. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:696-710. [PMID: 34626184 DOI: 10.1093/jxb/erab448] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 10/08/2021] [Indexed: 06/13/2023]
Abstract
Pollen tube growth and penetration in female tissues are essential for the transfer of sperm to the embryo sac during plant pollination. Despite its importance during pollination, little is known about the mechanisms that mediate pollen tube growth in female tissues. In this study, we identified an Arabidopsis thaliana pollen/pollen tube-specific gene, SKU5-SIMILAR 13 (SKS13), which was critical for the growth of pollen tubes in the transmitting tract. The SKS13 protein was distributed throughout the cytoplasm and pollen tube walls at the apical region. In comparison with wild-type pollen tubes, those of the sks13 mutants burst more frequently when grown in vitro. Additionally, the growth of sks13 pollen tubes was retarded in the transmitting tract, thereby resulting in decreased male fertility. The accumulation of pectin and cellulose in the cell wall of sks13 pollen tubes was altered, and the content of jasmonic acid (JA) in sks13 pollen was reduced. The pollen tubes treated with an inhibitor of JA biosynthesis grew much more slowly and had an altered distribution of pectin, which is similar to the pollen tube phenotypes of the SKS13 mutation. Our results suggest that SKS13 is essential for pollen tube growth in the transmitting tract by mediating the biosynthesis of JA that modifies the components of pollen tube cell walls.
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Yu J, Wang B, Fan W, Fan S, Xu Y, Liu C, Lv T, Liu W, Wu L, Xian L, Li T. Polyamines Involved in Regulating Self-Incompatibility in Apple. Genes (Basel) 2021; 12:1797. [PMID: 34828403 PMCID: PMC8620888 DOI: 10.3390/genes12111797] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 11/08/2021] [Accepted: 11/09/2021] [Indexed: 12/30/2022] Open
Abstract
Apple exhibits typical gametophytic self-incompatibility, in which self-S-RNase can arrest pollen tube growth, leading to failure of fertilization. To date, there have been few studies on how to resist the toxicity of self-S-RNase. In this study, pollen tube polyamines were found to respond to self-S-RNase and help pollen tubes defend against self-S-RNase. In particular, the contents of putrescine, spermidine, and spermine in the pollen tube treated with self-S-RNase were substantially lower than those treated with non-self-S-RNase. Further analysis of gene expression of key enzymes in the synthesis and degradation pathways of polyamines found that the expression of DIAMINE OXIDASE 4 (MdDAO4) as well as several polyamine oxidases such as POLYAMINE OXIDASES 3 (MdPAO3), POLYAMINE OXIDASES 4 (MdPAO4), and POLYAMINE OXIDASES 6 (MdPAO6) were significantly up-regulated under self-S-RNase treatment, resulting in the reduction of polyamines. Silencing MdPAO6 in pollen tubes alleviates the inhibitory effect of self-S-RNase on pollen tube growth. In addition, exogenous polyamines also enhance pollen tube resistance to self-S-RNase. Transcriptome sequencing data found that polyamines may communicate with S-RNase through the calcium signal pathway, thereby regulating the growth of the pollen tubes. To summarize, our results suggested that polyamines responded to the self-incompatibility reaction and could enhance pollen tube tolerance to S-RNase, thus providing a potential way to break self-incompatibility in apple.
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A Decade of Pollen Phosphoproteomics. Int J Mol Sci 2021; 22:ijms222212212. [PMID: 34830092 PMCID: PMC8619407 DOI: 10.3390/ijms222212212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/01/2021] [Accepted: 11/08/2021] [Indexed: 12/15/2022] Open
Abstract
Angiosperm mature pollen represents a quiescent stage with a desiccated cytoplasm surrounded by a tough cell wall, which is resistant to the suboptimal environmental conditions and carries the genetic information in an intact stage to the female gametophyte. Post pollination, pollen grains are rehydrated, activated, and a rapid pollen tube growth starts, which is accompanied by a notable metabolic activity, synthesis of novel proteins, and a mutual communication with female reproductive tissues. Several angiosperm species (Arabidopsis thaliana, tobacco, maize, and kiwifruit) were subjected to phosphoproteomic studies of their male gametophyte developmental stages, mostly mature pollen grains. The aim of this review is to compare the available phosphoproteomic studies and to highlight the common phosphoproteins and regulatory trends in the studied species. Moreover, the pollen phosphoproteome was compared with root hair phosphoproteome to pinpoint the common proteins taking part in their tip growth, which share the same cellular mechanisms.
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Westermann J. Two Is Company, but Four Is a Party-Challenges of Tetraploidization for Cell Wall Dynamics and Efficient Tip-Growth in Pollen. PLANTS (BASEL, SWITZERLAND) 2021; 10:plants10112382. [PMID: 34834745 PMCID: PMC8623246 DOI: 10.3390/plants10112382] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/01/2021] [Accepted: 11/03/2021] [Indexed: 05/27/2023]
Abstract
Some cells grow by an intricately coordinated process called tip-growth, which allows the formation of long tubular structures by a remarkable increase in cell surface-to-volume ratio and cell expansion across vast distances. On a broad evolutionary scale, tip-growth has been extraordinarily successful, as indicated by its recurrent 're-discovery' throughout evolutionary time in all major land plant taxa which allowed for the functional diversification of tip-growing cell types across gametophytic and sporophytic life-phases. All major land plant lineages have experienced (recurrent) polyploidization events and subsequent re-diploidization that may have positively contributed to plant adaptive evolutionary processes. How individual cells respond to genome-doubling on a shorter evolutionary scale has not been addressed as elaborately. Nevertheless, it is clear that when polyploids first form, they face numerous important challenges that must be overcome for lineages to persist. Evidence in the literature suggests that tip-growth is one of those processes. Here, I discuss the literature to present hypotheses about how polyploidization events may challenge efficient tip-growth and strategies which may overcome them: I first review the complex and multi-layered processes by which tip-growing cells maintain their cell wall integrity and steady growth. I will then discuss how they may be affected by the cellular changes that accompany genome-doubling. Finally, I will depict possible mechanisms polyploid plants may evolve to compensate for the effects caused by genome-doubling to regain diploid-like growth, particularly focusing on cell wall dynamics and the subcellular machinery they are controlled by.
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Tian X, Wang X, Li Y. Myosin XI-B is involved in the transport of vesicles and organelles in pollen tubes of Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1145-1161. [PMID: 34559914 DOI: 10.1111/tpj.15505] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 09/09/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
The movement of organelles and vesicles in pollen tubes depends on F-actin. However, the molecular mechanism through which plant myosin XI drives the movement of organelles is still controversial, and the relationship between myosin XI and vesicle movement in pollen tubes is also unclear. In this study, we found that the siliques of the myosin xi-b/e mutant were obviously shorter than those of the wild-type (WT) and that the seed set of the mutant was severely deficient. The pollen tube growth of myosin xi-b/e was significantly inhibited both in vitro and in vivo. Fluorescence recovery after photobleaching showed that the velocity of vesicle movement in the pollen tube tip of the myosin xi-b/e mutant was lower than that of the WT. It was also found that peroxisome movement was significantly inhibited in the pollen tubes of the myosin xi-b/e mutant, while the velocities of the Golgi stack and mitochondrial movement decreased relatively less in the pollen tubes of the mutant. The endoplasmic reticulum streaming in the pollen tube shanks was not significantly different between the WT and the myosin xi-b/e mutant. In addition, we found that myosin XI-B-GFP colocalized obviously with vesicles and peroxisomes in the pollen tubes of Arabidopsis. Taken together, these results indicate that myosin XI-B may bind mainly to vesicles and peroxisomes, and drive their movement in pollen tubes. These results also suggest that the mechanism by which myosin XI drives organelle movement in plant cells may be evolutionarily conserved compared with other eukaryotic cells.
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Kou X, Sun J, Wang P, Wang D, Cao P, Lin J, Chang Y, Zhang S, Wu J. PbrRALF2-elicited reactive oxygen species signaling is mediated by the PbrCrRLK1L13-PbrMPK18 module in pear pollen tubes. HORTICULTURE RESEARCH 2021; 8:222. [PMID: 34608125 PMCID: PMC8490453 DOI: 10.1038/s41438-021-00684-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 07/26/2021] [Accepted: 08/04/2021] [Indexed: 06/13/2023]
Abstract
Rapid alkalinization factors (RALFs) are cysteine-rich peptides that play important roles in a variety of biological processes, such as cell elongation and immune signaling. Recent studies in Arabidopsis have shown that RALFs regulate pollen tube growth via plasma membrane receptor-like kinases (RLKs). However, the downstream signal transduction mechanisms of RLKs in pollen tubes are unknown. Here, we identified PbrRALF2, a pear (Pyrus bretschneideri) pollen RALF peptide that inhibits pollen tube growth. We found that PbrRALF2 interacts with a malectin-like domain-containing RLK, PbrCrRLK1L13. The relative affinity between PbrRALF2 and PbrCrRLK1L13 was at the submicromolar level, which is consistent with the values of ligand-receptor kinase pairs and the physiological concentration for PbrRALF2-mediated inhibition of pollen tube growth. After binding to its extracellular domain, PbrRALF2 activated the phosphorylation of PbrCrRLK1L13 in a dose-dependent manner. We further showed that the MAP kinase PbrMPK18 is a downstream target of PbrCrRLK1L13 that mediates PbrRALF2-elicited reactive oxygen species (ROS) production. The excessive accumulation of ROS inhibits pollen tube growth. We show that MPK acts as a mediator for CrRLK1L to stimulate ROS production, which might represent a general mechanism by which RALF and CrRLK1L function in signaling pathways.
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Kim MJ, Jeon BW, Oh E, Seo PJ, Kim J. Peptide Signaling during Plant Reproduction. TRENDS IN PLANT SCIENCE 2021; 26:822-835. [PMID: 33715959 DOI: 10.1016/j.tplants.2021.02.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 02/02/2021] [Accepted: 02/17/2021] [Indexed: 05/08/2023]
Abstract
Plant signaling peptides are involved in cell-cell communication networks and coordinate a wide range of plant growth and developmental processes. Signaling peptides generally bind to receptor-like kinases, inducing their dimerization with co-receptors for signaling activation to trigger cellular signaling and biological responses. Fertilization is an important life event in flowering plants, involving precise control of cell-cell communications between male and female tissues. Peptide-receptor-like kinase-mediated signaling plays an important role in male-female interactions for successful fertilization in flowering plants. Here, we describe the recent findings on the functions and signaling pathways of peptides and receptors involved in plant reproduction processes including pollen germination, pollen tube growth, pollen tube guidance to the embryo sac, and sperm cell reception in female tissues.
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Christensen SM, Munkres I, Vannette RL. Nectar bacteria stimulate pollen germination and bursting to enhance microbial fitness. Curr Biol 2021; 31:4373-4380.e6. [PMID: 34324834 DOI: 10.1016/j.cub.2021.07.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/27/2021] [Accepted: 07/08/2021] [Indexed: 12/27/2022]
Abstract
Many organisms consume pollen, yet mechanisms of its digestion remain a fundamental enigma in pollination biology,1-3 as pollen is protected by a recalcitrant outer shell.4-8 Pollen is commonly found in floral nectar,9,10 as are nectar microbes, which are nearly ubiquitous among flowers.11-13 Nectar specialist bacteria, like Acinetobacter, can reach high densities (up to 109 cells/mL), despite the fact that floral nectar is nitrogen poor.14-17 Here, we show evidence that the genus Acinetobacter, prevalent nectar- and bee-associated bacteria,12,18-20 can induce pollen germination and bursting, gain access to protoplasm nutrients, and thereby grow to higher densities. Although induced germination had been suggested as a potential method in macroscopic pollen consumers,2,21-23 and fungal inhibition of pollen germination has been shown,24-27 direct biological induction of germination has not been empirically documented outside of plants.28-32Acinetobacter pollinis SCC47719 induced over 5× greater pollen germination and 20× greater pollen bursting than that of uninoculated pollen by 45 min. When provided with germinable pollen, A. pollinis stimulates protein release and grows to nearly twice the density compared to growth with ungerminable pollen, indicating that stimulation of germination benefits bacterial fitness. In contrast, a common nectar-inhabiting yeast (Metschnikowia)33 neither induced nor benefited from pollen germination. We conclude that Acinetobacter both specifically causes and benefits from inducing pollen germination and bursting. Further study of microbe-pollen interactions may inform many aspects of pollination ecology, including floral microbial ecology,34,35 pollinator nutrient acquisition from pollen,2,3,21,36 and cues of pollen germination for plant reproduction.37-39.
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Máthé C, Nick P, Pasternak TP. Editorial: How Cells Build Plants: Regulatory Mechanisms for Integrated Functioning of Plant Cells and the Whole Plant Body. FRONTIERS IN PLANT SCIENCE 2021; 12:706892. [PMID: 34295348 PMCID: PMC8291082 DOI: 10.3389/fpls.2021.706892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2021] [Accepted: 06/11/2021] [Indexed: 06/13/2023]
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Jia Q, Zhang S, Lin Y, Zhang J, Li L, Chen H, Zhang Q. Phospholipase Dδ regulates pollen tube growth by modulating actin cytoskeleton organization in Arabidopsis. PLANT SIGNALING & BEHAVIOR 2021; 16:1915610. [PMID: 33853512 PMCID: PMC8205101 DOI: 10.1080/15592324.2021.1915610] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 04/07/2021] [Accepted: 04/07/2021] [Indexed: 05/19/2023]
Abstract
The actin cytoskeleton plays pivotal roles in pollen tube growth by regulating organelle movement, cytoplasmic streaming, and vesicle trafficking. Previous studies have reported that plasma membrane-localized phospholipase Dδ (PLDδ) binds to cortical microtubules and negatively regulates plant stress tolerance. However, it remains unknown whether or how PLDδ regulates microfilament organization. In this study, we found that loss of PLDδ function led to a significant increase in pollen tube growth, whereas PLDδ overexpression resulted in pollen tube growth inhibition. We also found that wild-type PLDδ, rather than Arg 622-mutated PLDδ, complemented the pldδ phenotype in pollen tubes. In vitro biochemical assays demonstrated that PLDδ binds directly to F-actin, and immunofluorescence assays revealed that PLDδ in pollen tubes influences actin organization. Together, these results suggest that PLDδ participates in the development of pollen tube growth by organizing actin filaments.
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Breygina M, Klimenko E, Shilov E, Podolyan A, Mamaeva A, Zgoda V, Fesenko I. Hydrogen peroxide in tobacco stigma exudate affects pollen proteome and membrane potential in pollen tubes. PLANT BIOLOGY (STUTTGART, GERMANY) 2021; 23:592-602. [PMID: 33745193 DOI: 10.1111/plb.13255] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 03/12/2021] [Indexed: 06/12/2023]
Abstract
ROS are known to be accumulated in stigmas of different species and can possibly perform different functions important for plant reproduction. Here we tested the assumption that one of their functions is to control membrane potential and provoke synthesis of unique proteins in germinating pollen. We used spectrofluorometry and spectrophotometry to detect H2 O2 in stigma exudate, quantitative fluorescent microscopy of pollen tubes and flow cytometry of pollen protoplasts to reveal effects on membrane potential, and a label-free quantification approach to study pollen proteome changes after H2 O2 treatment. We found that in both growing pollen tubes and pollen protoplasts exudate causes plasmalemma hyperpolarization similar to that provoked by H2 O2 . This effect is abolished by catalase treatment and the ROS quencher, MnTMPP. Inhibitory analysis indicates probable participation of Ca2+ - and K+ -conducting channels in the observed hyperpolarization. For a deeper understanding of pollen response, we analysed proteome alterations in H2 O2 -treated pollen grains. We found 50 unique proteins and 20 differently accumulated proteins that are mainly involved in cell metabolism, energetics, protein synthesis and folding. Observed hyperpolarization and proteome alterations agree well with previously reported stimulation of pollen germination by H2 O2 and sensitivity of Ca2+ - and K+ -conducting channels to this ROS. Thus, H2 O2 is one of the active substances in tobacco stigma exudate that stimulates various physiological processes in germinating pollen.
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Ke CJ, Lin XJ, Zhang BY, Chen LY. Turgor regulation defect 1 proteins play a conserved role in pollen tube reproductive innovation of the angiosperms. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 106:1356-1365. [PMID: 33735469 DOI: 10.1111/tpj.15241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/11/2021] [Accepted: 03/16/2021] [Indexed: 06/12/2023]
Abstract
Sexual reproduction in angiosperms is siphonogamous, and the interaction between pollen tube and pistil is critical for successful fertilization. Our previous study demonstrated that mutation of the Arabidopsis turgor regulation defect 1 (TOD1) gene leads to reduced male fertility, a result of retarded pollen tube growth in the pistil. TOD1 encodes a Golgi-localized alkaline ceramidase, a key enzyme for the production of sphingosine-1-phosphate (S1P), which is involved in the regulation of turgor pressure in plant cells. However, whether TOD1s play a conserved role in the innovation of siphonogamy is largely unknown. In this study, we provide evidence that OsTOD1, which is similar to AtTOD1, is also preferentially expressed in rice pollen grains and pollen tubes. OsTOD1 knockout results in reduced pollen tube growth potential in rice pistil. Both the OsTOD1 genomic sequence with its own promoter and the coding sequence under the AtTOD1 promoter can partially rescue the attod1 mutant phenotype. Furthermore, TOD1s from other angiosperm species can partially rescue the attod1 mutant phenotype, while TOD1s from gymnosperm species are not able to complement the attod1 mutant phenotype. Our data suggest that TOD1 acts conservatively in angiosperms, and this opens up an opportunity to dissect the role of sphingolipids in pollen tube growth in angiosperms.
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Li K, Prada J, Damineli DSC, Liese A, Romeis T, Dandekar T, Feijó JA, Hedrich R, Konrad KR. An optimized genetically encoded dual reporter for simultaneous ratio imaging of Ca 2+ and H + reveals new insights into ion signaling in plants. THE NEW PHYTOLOGIST 2021; 230:2292-2310. [PMID: 33455006 PMCID: PMC8383442 DOI: 10.1111/nph.17202] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 12/23/2020] [Indexed: 05/07/2023]
Abstract
Whereas the role of calcium ions (Ca2+ ) in plant signaling is well studied, the physiological significance of pH-changes remains largely undefined. Here we developed CapHensor, an optimized dual-reporter for simultaneous Ca2+ and pH ratio-imaging and studied signaling events in pollen tubes (PTs), guard cells (GCs), and mesophyll cells (MCs). Monitoring spatio-temporal relationships between membrane voltage, Ca2+ - and pH-dynamics revealed interconnections previously not described. In tobacco PTs, we demonstrated Ca2+ -dynamics lag behind pH-dynamics during oscillatory growth, and pH correlates more with growth than Ca2+ . In GCs, we demonstrated abscisic acid (ABA) to initiate stomatal closure via rapid cytosolic alkalization followed by Ca2+ elevation. Preventing the alkalization blocked GC ABA-responses and even opened stomata in the presence of ABA, disclosing an important pH-dependent GC signaling node. In MCs, a flg22-induced membrane depolarization preceded Ca2+ -increases and cytosolic acidification by c. 2 min, suggesting a Ca2+ /pH-independent early pathogen signaling step. Imaging Ca2+ and pH resolved similar cytosol and nuclear signals and demonstrated flg22, but not ABA and hydrogen peroxide to initiate rapid membrane voltage-, Ca2+ - and pH-responses. We propose close interrelation in Ca2+ - and pH-signaling that is cell type- and stimulus-specific and the pH having crucial roles in regulating PT growth and stomata movement.
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Zhang B, Zhang C, Liu C, Fu A, Luan S. A Golgi-localized manganese transporter functions in pollen tube tip growth to control male fertility in Arabidopsis. PLANT COMMUNICATIONS 2021; 2:100178. [PMID: 34027392 PMCID: PMC8132125 DOI: 10.1016/j.xplc.2021.100178] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/23/2021] [Accepted: 03/12/2021] [Indexed: 05/12/2023]
Abstract
Manganese (Mn) serves as an essential cofactor for many enzymes in various compartments of a plant cell. Allocation of Mn among various organelles thus plays a central role in Mn homeostasis to support metabolic processes. We report the identification of a Golgi-localized Mn transporter (named PML3) that is essential for rapid cell elongation in young tissues such as emerging leaves and the pollen tube. In particular, the pollen tube defect in the pml3 loss-of-function mutant caused severe reduction in seed yield, a critical agronomic trait. Further analysis suggested that a loss of pectin deposition in the pollen tube might cause the pollen tube to burst and slow its elongation, leading to decreased male fertility. As the Golgi apparatus serves as the major hub for biosynthesis and modification of cell-wall components, PML3 may function in Mn homeostasis of this organelle, thereby controlling metabolic and/or trafficking processes required for pectin deposition in rapidly elongating cells.
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Rafińska K, Niedojadło K, Świdziński M, Niedojadło J, Bednarska-Kozakiewicz E. Spatial and Temporal Distribution of Arabinogalactan Proteins during Larix decidua Mill. Male Gametophyte and Ovule Interaction. Int J Mol Sci 2021; 22:ijms22094298. [PMID: 33919026 PMCID: PMC8122408 DOI: 10.3390/ijms22094298] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/13/2021] [Accepted: 04/16/2021] [Indexed: 12/17/2022] Open
Abstract
The role of ArabinoGalactan Proteins (AGPs) in the sexual reproduction of gymnosperms is not as well documented as that of angiosperms. In earlier studies, we demonstrated that AGPs play important roles during ovule differentiation in Larix decidua Mill. The presented results encouraged us to carry out further studies focused on the functions of these unique glycoproteins during pollen/pollen tube and ovule interactions in Larix. We identified and analyzed the localization of AGPs epitopes by JIM4, JIM8, JIM13 and LM2 antibodies (Abs) in male gametophytes and ovule tissue during pollination, the progamic phase, and after fertilization and in vitro growing pollen tubes. Our results indicated that (1) AGPs recognized by JIM4 Abs play an essential role in the interaction of male gametophytes and ovules because their appearance in ovule cells is induced by physical contact between reproductive partners; (2) after pollination, AGPs are secreted from the pollen cytoplasm into the pollen wall and contact the extracellular matrix of stigmatic tip cells followed by micropylar canal cells; (3) AGPs synthesized in nucellus cells before pollen grain germination are secreted during pollen tube growth into the extracellular matrix, where they can directly interact with male gametophytes; (4) in vitro cultured pollen tube AGPs labeled with LM2 Abs participate in the germination of pollen grain, while AGPs recognized by JIM8 Abs are essential for pollen tube tip growth.
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Zhou Y, Ding M, Duan X, Konrad KR, Nagel G, Gao S. Extending the Anion Channelrhodopsin-Based Toolbox for Plant Optogenetics. MEMBRANES 2021; 11:membranes11040287. [PMID: 33919843 PMCID: PMC8070814 DOI: 10.3390/membranes11040287] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/07/2021] [Accepted: 04/09/2021] [Indexed: 11/16/2022]
Abstract
Optogenetics was developed in the field of neuroscience and is most commonly using light-sensitive rhodopsins to control the neural activities. Lately, we have expanded this technique into plant science by co-expression of a chloroplast-targeted β-carotene dioxygenase and an improved anion channelrhodopsin GtACR1 from the green alga Guillardia theta. The growth of Nicotiana tabacum pollen tube can then be manipulated by localized green light illumination. To extend the application of analogous optogenetic tools in the pollen tube system, we engineered another two ACRs, GtACR2, and ZipACR, which have different action spectra, light sensitivity and kinetic features, and characterized them in Xenopus laevis oocytes, Nicotiana benthamiana leaves and N. tabacum pollen tubes. We found that the similar molecular engineering method used to improve GtACR1 also enhanced GtACR2 and ZipACR performance in Xenopus laevis oocytes. The ZipACR1 performed in N. benthamiana mesophyll cells and N. tabacum pollen tubes with faster kinetics and reduced light sensitivity, allowing for optogenetic control of anion fluxes with better temporal resolution. The reduced light sensitivity would potentially facilitate future application in plants, grown under low ambient white light, combined with an optogenetic manipulation triggered by stronger green light.
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Yang H, You C, Yang S, Zhang Y, Yang F, Li X, Chen N, Luo Y, Hu X. The Role of Calcium/Calcium-Dependent Protein Kinases Signal Pathway in Pollen Tube Growth. FRONTIERS IN PLANT SCIENCE 2021; 12:633293. [PMID: 33767718 PMCID: PMC7985351 DOI: 10.3389/fpls.2021.633293] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 02/15/2021] [Indexed: 05/21/2023]
Abstract
Pollen tube (PT) growth as a key step for successful fertilization is essential for angiosperm survival and especially vital for grain yield in cereals. The process of PT growth is regulated by many complex and delicate signaling pathways. Among them, the calcium/calcium-dependent protein kinases (Ca2+/CPKs) signal pathway has become one research focus, as Ca2+ ion is a well-known essential signal molecule for PT growth, which can be instantly sensed and transduced by CPKs to control myriad biological processes. In this review, we summarize the recent progress in understanding the Ca2+/CPKs signal pathway governing PT growth. We also discuss how this pathway regulates PT growth and how reactive oxygen species (ROS) and cyclic nucleotide are integrated by Ca2+ signaling networks.
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