-
Nature Communications Jan 2023Pollen tube guidance within female tissues of flowering plants can be divided into preovular guidance, ovular guidance and a connecting stage called pollen tube...
Pollen tube guidance within female tissues of flowering plants can be divided into preovular guidance, ovular guidance and a connecting stage called pollen tube emergence. As yet, no female factor has been identified to positively regulate this transition process. In this study, we show that an ovary-expressed bHLH transcription factor Cucumis sativus ALCATRAZ (CsALC) functions in pollen tube emergence in cucumber. CsALC knockout mutants showed diminished pollen tube emergence, extremely reduced entry into ovules, and a 95% reduction in female fertility. Further examination showed two rapid alkalinization factors CsRALF4 and CsRALF19 were less expressed in Csalc ovaries compared to WT. Besides the loss of male fertility derived from precocious pollen tube rupture as in Arabidopsis, Csralf4 Csralf19 double mutants exhibited a 60% decrease in female fertility due to reduced pollen tube distribution and decreased ovule targeting efficiency. In brief, CsALC regulates female fertility and promotes CsRALF4/19 expression in the ovary during pollen tube guidance in cucumber.
Topics: Cucumis sativus; Ovary; Pollen Tube; Arabidopsis; Arabidopsis Proteins; Ovule
PubMed: 36650145
DOI: 10.1038/s41467-023-35936-z -
Science Advances Oct 2016In angiosperms, pollen tubes carry two sperm cells toward the egg and central cells to complete double fertilization. In animals, not only sperm but also seminal plasma...
In angiosperms, pollen tubes carry two sperm cells toward the egg and central cells to complete double fertilization. In animals, not only sperm but also seminal plasma is required for proper fertilization. However, little is known regarding the function of pollen tube content (PTC), which is analogous to seminal plasma. We report that the PTC plays a vital role in the prefertilization state and causes an enlargement of ovules without fertilization. We termed this phenomenon as pollen tube-dependent ovule enlargement morphology and placed it between pollen tube guidance and double fertilization. Additionally, PTC increases endosperm nuclei without fertilization when combined with autonomous endosperm mutants. This finding could be applied in agriculture, particularly in enhancing seed formation without fertilization in important crops.
Topics: Arabidopsis; Mutation; Ovule; Pollen Tube; Seeds
PubMed: 27819041
DOI: 10.1126/sciadv.1600554 -
The New Phytologist Jul 2021We have recently characterised NET2A as a pollen-specific actin-binding protein that binds F-actin at the plasma membrane of growing pollen tubes. However, the role of...
We have recently characterised NET2A as a pollen-specific actin-binding protein that binds F-actin at the plasma membrane of growing pollen tubes. However, the role of NET2 proteins in pollen development and fertilisation have yet to be elucidated. To further characterise the role of Arabidopsis NET2 proteins in pollen development and fertilisation, we analysed the subcellular localisation of NET2A over the course of pollen grain development and investigated the role of the NET2 family using net2 loss-of-function mutants. We observed NET2A to localise to the F-actin cytoskeleton in developing pollen grains as it underwent striking structural reorganisations at specific stages of development and during germination and pollen tube growth. Furthermore, net2 loss-of-function mutants exhibited striking morphological defects in the early stages of pollen tube growth, arising from frequent changes to pollen tube growth trajectory. We observed defects in the cortical actin cytoskeleton and actin-driven subcellular processes in net2 mutant pollen tubes. We demonstrate that NET2 proteins are essential for normal actin-driven pollen development highlighting an important role for the NET2 family members in regulating pollen tube growth during fertilisation.
Topics: Actin Cytoskeleton; Actins; Arabidopsis; Arabidopsis Proteins; Pollen Tube; Pollination
PubMed: 33864269
DOI: 10.1111/nph.17391 -
The New Phytologist Jan 2012• Fusion of floral carpels (syncarpy) in angiosperms is thought to have allowed for significant improvements in offspring quantity and quality in syncarpous species...
• Fusion of floral carpels (syncarpy) in angiosperms is thought to have allowed for significant improvements in offspring quantity and quality in syncarpous species over gymnosperms and apocarpous (free-carpelled) angiosperms. Given the disadvantages of apocarpy, it remains an evolutionary puzzle why many angiosperm lineages with free carpels (apocarpy) have been so successful and why some lineages show reversals to apocarpy. • To investigate whether some advantages of syncarpy may accrue in other ways to apocarpous species, we reviewed previous studies of pollen-tube growth in apocarpous species and also documented pollen-tube growth in nine additional apocarpous species in six families. • Anatomical studies of a scattering of apocarpous paleodicots, monocots, and eudicots show that, after transiting the style, 'extra' pollen tubes exit fully fertilized carpels and grow to other carpels with unfertilized ovules. In many species this occurs via openings in the simple carpels, as we report here for Sagittaria potamogetifolia, Sagittaria pygmaea, Sedum lineare, and Schisandra sphenanthera. • The finding that extra-gynoecial pollen-tube growth is widespread in apocarpous species eliminates the possibility of a major fitness cost of apocarpy relative to syncarpy and may help to explain the persistence of, and multiple reversals to, apocarpy in the evolutionary history of angiosperms.
Topics: Adaptation, Physiological; Data Collection; Phylogeny; Pollen Tube; Sagittaria
PubMed: 21955061
DOI: 10.1111/j.1469-8137.2011.03912.x -
The Plant Journal : For Cell and... Aug 2020HYDROXYPROLINE O-ARABINOSYLTRANSFERASEs (HPATs) initiate a post-translational protein modification (Hyp-Ara) found abundantly on cell wall structural proteins. In...
HYDROXYPROLINE O-ARABINOSYLTRANSFERASEs (HPATs) initiate a post-translational protein modification (Hyp-Ara) found abundantly on cell wall structural proteins. In Arabidopsis thaliana, HPAT1 and HPAT3 are redundantly required for full pollen fertility. In addition to the lack of Hyp-Ara in hpat1/3 pollen tubes (PTs), we also found broadly disrupted cell wall polymer distributions, particularly the conversion of the tip cell wall to a more shaft-like state. Mutant PTs were slow growing and prone to rupture and morphological irregularities. In a forward mutagenesis screen for suppressors of the hpat1/3 low seed-set phenotype, we identified a missense mutation in exo70a2, a predicted member of the vesicle-tethering exocyst complex. The suppressed pollen had increased fertility, fewer morphological defects and partially rescued cell wall organization. A transcriptional null allele of exo70a2 also suppressed the hpat1/3 fertility phenotype, as did mutants of core exocyst complex member sec15a, indicating that reduced exocyst function bypassed the PT requirement for Hyp-Ara. In a wild-type background, exo70a2 reduced male transmission efficiency, lowered pollen germination frequency and slowed PT elongation. EXO70A2 also localized to the PT tip plasma membrane, consistent with a role in exocyst-mediated secretion. To monitor the trafficking of Hyp-Ara modified proteins, we generated an HPAT-targeted fluorescent secretion reporter. Reporter secretion was partially dependent on EXO70A2 and was significantly increased in hpat1/3 PTs compared with the wild type, but was reduced in the suppressed exo70a2 hpat1/3 tubes.
Topics: Arabidopsis; Arabidopsis Proteins; Cell Wall; Hydroxyproline; Mutation; Pentosyltransferases; Pollen Tube
PubMed: 32391581
DOI: 10.1111/tpj.14808 -
Plant Physiology Jul 2016Root hair cells and pollen tubes, like fungal hyphae, possess a typical tip or polar cell expansion with growth limited to the apical dome. Cell expansion needs to be... (Review)
Review
Root hair cells and pollen tubes, like fungal hyphae, possess a typical tip or polar cell expansion with growth limited to the apical dome. Cell expansion needs to be carefully regulated to produce a correct shape and size. Polar cell growth is sustained by oscillatory feedback loops comprising three main components that together play an important role regulating this process. One of the main components are reactive oxygen species (ROS) that, together with calcium ions (Ca(2+)) and pH, sustain polar growth over time. Apoplastic ROS homeostasis controlled by NADPH oxidases as well as by secreted type III peroxidases has a great impact on cell wall properties during cell expansion. Polar growth needs to balance a focused secretion of new materials in an extending but still rigid cell wall in order to contain turgor pressure. In this review, we discuss the gaps in our understanding of how ROS impact on the oscillatory Ca(2+) and pH signatures that, coordinately, allow root hair cells and pollen tubes to expand in a controlled manner to several hundred times their original size toward specific signals.
Topics: Calcium; Cell Membrane; Cell Polarity; Cytoplasm; Homeostasis; Hydrogen-Ion Concentration; Peroxidases; Plant Cells; Plant Proteins; Plant Roots; Pollen Tube; Reactive Oxygen Species
PubMed: 27208283
DOI: 10.1104/pp.16.00191 -
The Plant Journal : For Cell and... Mar 2021Successful delivery of sperm cells to the embryo sac in higher plants is mediated by pollen tube growth. The molecular mechanisms underlying pollen germination and tube...
Successful delivery of sperm cells to the embryo sac in higher plants is mediated by pollen tube growth. The molecular mechanisms underlying pollen germination and tube growth in crop plants remain rather unclear, although these mechanisms are crucial to plant reproduction and seed formation. By screening pollen-specific gene mutants in rice (Oryza sativa), we identified a T-DNA insertional mutant of Germinating modulator of rice pollen (GORI) that showed a one-to-one segregation ratio for wild type (WT) to heterozygous. GORI encodes a seven-WD40-motif protein that is homologous to JINGUBANG/REN4 in Arabidopsis. GORI is specifically expressed in rice pollen, and its protein is localized in the nucleus, cytosol and plasma membrane. Furthermore, a homozygous mutant, gori-2, created through CRISPR-Cas9 clearly exhibited male sterility with disruption of pollen tube germination and elongation. The germinated pollen tube of gori-2 exhibited decreased actin filaments and altered pectin distribution. Transcriptome analysis revealed that 852 pollen-specific genes were downregulated in gori-2 compared with the WT, and Gene Ontology enrichment analysis indicated that these genes are strongly associated with cell wall modification and clathrin coat assembly. Based on the molecular features of GORI, phenotypical observation of the gori mutant and its interaction with endocytic proteins and Rac GTPase, we propose that GORI plays key roles in forming endo-/exocytosis complexes that could mediate pollen tube growth in rice.
Topics: Gene Expression Regulation, Plant; Germination; Oryza; Plant Proteins; Pollen Tube; RNA-Seq
PubMed: 33345419
DOI: 10.1111/tpj.15139 -
Plant Signaling & Behavior Sep 2016In order to provide more insight into the function of aquaporins during pollination, we characterized NIP4;1 and NIP4;2, 2 pollen-specific aquaporins of Arabidopsis...
In order to provide more insight into the function of aquaporins during pollination, we characterized NIP4;1 and NIP4;2, 2 pollen-specific aquaporins of Arabidopsis thaliana. NIP4;1 and NIP4;2 displayed high amino acid identity. RT-PCR and GUS promoter analysis showed that they have different expression patterns. NIP4;1 is expressed at low levels in mature pollen, while NIP4;2 is highly expressed only during pollen tube growth. Single T-DNA nip4;1 and nip4;2 mutants and double amiRNA nip4;1 nip4;2 knockdowns showed reduced male fertility due to deficient pollen germination and pollen tube length. Functional assays in oocytes showed that NIP4;1 and NIP4;2 transport water and nonionic solutes. Here, the participation of the different pollen aquaporins in pollen hydration and pollen tube growth is discussed.
Topics: Aquaporins; Arabidopsis; Arabidopsis Proteins; Pollen Tube; Pollination; Promoter Regions, Genetic
PubMed: 27598621
DOI: 10.1080/15592324.2016.1217375 -
Proceedings of the National Academy of... Nov 2018The -Golgi network (TGN) is an essential tubular-vesicular organelle derived from the Golgi and functions as an independent sorting and trafficking hub within the cell....
The -Golgi network (TGN) is an essential tubular-vesicular organelle derived from the Golgi and functions as an independent sorting and trafficking hub within the cell. However, the molecular regulation of TGN biogenesis remains enigmatic. Here we identified an mutant loss of TGN () that is defective in TGN formation and sterile due to impaired pollen tube growth in the style. The mutation leads to overstacking of the Golgi cisternae and significant reduction in the number of TGNs and vesicles surrounding the Golgi in pollen, which is corroborated by the dispersed cytosolic distribution of TGN-localized proteins. Consistently, deposition of extracellular pectin and plasma membrane localization of kinases and phosphoinositide species are also impaired. Subcellular localization analysis suggests that LOT is localized on the periphery of the Golgi cisternae, but the mutation does not affect the localization of Golgi-resident proteins. Furthermore, the yeast complementation result suggests that LOT could functionally act as a component of the guanine nucleotide exchange factor (GEF) complex of small Rab GTPase Ypt6. Taken together, these findings suggest that LOT is a critical player for TGN biogenesis in the plant lineage.
Topics: Arabidopsis; Arabidopsis Proteins; Golgi Apparatus; Golgi Matrix Proteins; Guanine Nucleotide Exchange Factors; Intracellular Signaling Peptides and Proteins; Pollen Tube; Protein Transport; trans-Golgi Network
PubMed: 30413616
DOI: 10.1073/pnas.1809206115 -
The Plant Journal : For Cell and... Jul 2020Plant cell wall remodeling plays a key role in the control of cell elongation and differentiation. In particular, fine-tuning of the degree of methylesterification of...
Plant cell wall remodeling plays a key role in the control of cell elongation and differentiation. In particular, fine-tuning of the degree of methylesterification of pectins was previously reported to control developmental processes as diverse as pollen germination, pollen tube elongation, emergence of primordia or elongation of dark-grown hypocotyls. However, how pectin degradation can modulate plant development has remained elusive. Here we report the characterization of a polygalacturonase (PG), AtPGLR, the gene for which is highly expressed at the onset of lateral root emergence in Arabidopsis. Due to gene compensation mechanisms, mutant approaches failed to determine the involvement of AtPGLR in plant growth. To overcome this issue, AtPGLR has been expressed heterologously in the yeast Pichia pastoris and biochemically characterized. We showed that AtPGLR is an endo-PG that preferentially releases non-methylesterified oligogalacturonides with a short degree of polymerization (< 8) at acidic pH. The application of the purified recombinant protein on Amaryllis pollen tubes, an excellent model for studying cell wall remodeling at acidic pH, induced abnormal pollen tubes or cytoplasmic leakage in the subapical dome of the pollen tube tip, where non-methylesterified pectin epitopes are detected. Those leaks could either be repaired by new β-glucan deposits (mostly callose) in the cell wall or promoted dramatic burst of the pollen tube. Our work presents the full biochemical characterization of an Arabidopsis PG and highlights the importance of pectin integrity in pollen tube elongation.
Topics: Arabidopsis; Arabidopsis Proteins; Plant Roots; Plants, Genetically Modified; Pollen Tube; Polygalacturonase; Saccharomycetales
PubMed: 32215973
DOI: 10.1111/tpj.14753