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Journal of Experimental Botany Apr 2020
Topics: Arabidopsis; Genome-Wide Association Study; Plant Cells; Plant Roots; Pollen Tube
PubMed: 32324242
DOI: 10.1093/jxb/eraa163 -
ELife Sep 2020The pollen tube in a flowering plant grows in a direction that is influenced by the mechanical properties of the stigma papillae and the organization of structures...
The pollen tube in a flowering plant grows in a direction that is influenced by the mechanical properties of the stigma papillae and the organization of structures called cortical microtubules inside these cells.
Topics: Arabidopsis; Cell Wall; Katanin; Microtubules; Pollen Tube
PubMed: 32867921
DOI: 10.7554/eLife.61647 -
Molecular Breeding : New Strategies in... Apr 2023Pollen tube (PT) growth towards the micropyle is critical for successful double fertilization. However, the mechanism of micropyle-directed PT growth is still unclear in...
UNLABELLED
Pollen tube (PT) growth towards the micropyle is critical for successful double fertilization. However, the mechanism of micropyle-directed PT growth is still unclear in . In this study, two aspartate proteases, BnaAP36s and BnaAP39s, were identified in . BnaAP36s and BnaAP39s were localized to the plasma membrane. The homologues of and were highly expressed in flower organs, especially in the anther. Sextuple and double mutants of and were then generated using CRISPR/Cas9 technology. Compared to WT, the seed-set of and mutants was reduced by 50% and 60%, respectively. The reduction in seed-set was also found when and were used as the female parent in a reciprocal cross assay. Like WT, and pollen were able to germinate and the relative PTs were able to elongate in style. Approximately 36% and 33% of and PTs, respectively, failed to grow towards the micropyle, indicating that BnaAP36s and BnaAP39s are essential for micropyle-directed PT growth. Furthermore, Alexander's staining showed that 10% of pollen grains were aborted, but not , suggesting that may also affect microspore development. These results suggest that BnaAP36s and BnaAP39s play a critical role in the growth of micropyle-directed PTs in .
SUPPLEMENTARY INFORMATION
The online version contains supplementary material available at 10.1007/s11032-023-01377-1.
PubMed: 37313529
DOI: 10.1007/s11032-023-01377-1 -
Current Opinion in Plant Biology Oct 2019In flowering plants, extensive male-female interactions during pollen germination on the stigma, pollen tube growth and guidance in the transmitting tract, and pollen... (Review)
Review
In flowering plants, extensive male-female interactions during pollen germination on the stigma, pollen tube growth and guidance in the transmitting tract, and pollen tube reception by the female gametophyte are required for successful double fertilization in which various signaling cascades are involved. Peptide/receptor-like kinase-mediated signaling has been found playing important roles in these male-female interactions. Here, we mainly summarized the progress made on the regulatory roles of peptide/receptor-like kinase-mediated signaling pathways in four critical stages during reproduction in higher plants.
Topics: Female; Male; Ovule; Phosphotransferases; Pollen Tube; Pollination; Signal Transduction
PubMed: 30999163
DOI: 10.1016/j.pbi.2019.03.004 -
Plant, Cell & Environment Dec 2023Heat stress has a negative impact on pollen development in maize (Zea mays L.) but the postpollination events that determine kernel sterility are less well...
Heat stress has a negative impact on pollen development in maize (Zea mays L.) but the postpollination events that determine kernel sterility are less well characterised. The impact of short-term (hours) heat exposure during postpollination was therefore assessed in silks and ovaries. The temperatures inside the kernels housed within the husks was significantly lower than the imposed heat stress. This protected the ovaries and possibly the later phase of pollen tube growth from the adverse effects of heat stress. Failure of maize kernel fertilization was observed within 6 h of heat stress exposure postpollination. This was accompanied by a significant restriction of early pollen tube growth rather than pollen germination. Limitations on early pollen tube growth were therefore a major factor contributing to heat stress-induced kernel sterility. Exposure to heat stress altered the sugar composition of silks, suggesting that hexose supply contributed to the limitations on pollen tube growth. Moreover, the activities of sucrose metabolising enzymes, the expression of sucrose degradation and trehalose biosynthesis genes were decreased following heat stress. Significant increases in reactive oxygen species, abscisic acid and auxin levels accompanied by altered expression of phytohormone-related genes may also be important in the heat-induced suppression of pollen tube growth.
Topics: Pollen Tube; Zea mays; Infertility; Plant Growth Regulators; Sucrose
PubMed: 37623372
DOI: 10.1111/pce.14702 -
Frontiers in Plant Science 2020The growing pollen tube has become one of the most fascinating model cell systems for investigations into cell polarity and polar cell growth in plants. Rapidly growing... (Review)
Review
The growing pollen tube has become one of the most fascinating model cell systems for investigations into cell polarity and polar cell growth in plants. Rapidly growing pollen tubes achieve tip-focused cell expansion by vigorous anterograde exocytosis, through which various newly synthesized macromolecules are directionally transported and deposited at the cell apex. Meanwhile, active retrograde endocytosis counter balances the exocytosis at the tip which is believed to recycle the excessive exocytic components for multiple rounds of secretion. Therefore, apical exocytosis and endocytosis are the frontline cellular processes which drive the polar growth of pollen tubes, although they represent opposite vesicular trafficking events with distinct underpinning mechanisms. Nevertheless, the molecular basis governing the spatiotemporal crosstalk and counterbalance of exocytosis and endocytosis during pollen tube polarization and growth remains elusive. Here we discuss recent insight into exocytosis and endocytosis in sculpturing high rates of polarized pollen tube growth. In addition, we especially introduce the novel integration of mathematical modeling in uncovering the mysteries of cell polarity and polar cell growth.
PubMed: 33123182
DOI: 10.3389/fpls.2020.572848 -
Plant Reproduction Dec 2020Gametophytic cross-incompatibility systems in corn have been the subject of genetic studies for more than a century. They have tremendous economic potential as a genetic... (Review)
Review
Gametophytic cross-incompatibility systems in corn have been the subject of genetic studies for more than a century. They have tremendous economic potential as a genetic mechanism for controlling fertilization without controlling pollination. Three major genetically distinct and functionally equivalent cross-incompatibility systems exist in Zea mays: Ga1, Tcb1, and Ga2. All three confer reproductive isolation between maize or teosinte varieties with different haplotypes at any one locus. These loci confer genetically separable functions to the silk and pollen: a female function that allows the silk to block fertilization by non-self-type pollen and a male function that overcomes the block of the female function from the same locus. Identification of some of these genes has shed light on the reproductive isolation they confer. The identification of both male and female factors as pectin methylesterases reveals the importance of pectin methylesterase activity in controlling the decision between pollen acceptance versus rejection, possibly by regulating the degree of methylesterification of the pollen tube cell wall. The appropriate level and spatial distribution of pectin methylesterification is critical for pollen tube growth and is affected by both pectin methylesterases and pectin methylesterase inhibitors. We present a molecular model that explains how cross-incompatibility systems may function that can be tested in Zea and uncharacterized cross-incompatibility systems. Molecular characterization of these loci in conjunction with further refinement of the underlying molecular and cellular mechanisms will allow researchers to bring new and powerful tools to bear on understanding reproductive isolation in Zea mays and related species.
Topics: Breeding; Genes, Plant; Pollen; Pollen Tube; Pollination; Reproduction; Self-Incompatibility in Flowering Plants; Zea mays
PubMed: 32865620
DOI: 10.1007/s00497-020-00394-w -
International Journal of Molecular... Dec 2020Pollen grain is a unique haploid organism characterized by two key physiological processes: activation of metabolism upon exiting dormancy and polar tube growth. In... (Review)
Review
Pollen grain is a unique haploid organism characterized by two key physiological processes: activation of metabolism upon exiting dormancy and polar tube growth. In gymnosperms and flowering plants, these processes occur in different time frames and exhibit important features; identification of similarities and differences is still in the active phase. In angiosperms, the growth of male gametophyte is directed and controlled by its microenvironment, while in gymnosperms it is relatively autonomous. Recent reviews have detailed aspects of interaction between angiosperm female tissues and pollen such as interactions between peptides and their receptors; however, accumulated evidence suggests low-molecular communication, in particular, through ion exchange and ROS production, equally important for polar growth as well as for pollen germination. Recently, it became clear that ROS and ionic currents form a single regulatory module, since ROS production and the activity of ion transport systems are closely interrelated and form a feedback loop.
Topics: Cycadopsida; Germination; Homeostasis; Ions; Plants; Pollen; Reactive Oxygen Species; Reproduction; Signal Transduction
PubMed: 33322128
DOI: 10.3390/ijms21249476 -
The New Phytologist Sep 2023Pollen tubes have dynamic tubular vacuoles. Functional loss of AP-3, a regulator of one vacuolar trafficking route, reduces pollen tube growth. However, the role of...
Pollen tubes have dynamic tubular vacuoles. Functional loss of AP-3, a regulator of one vacuolar trafficking route, reduces pollen tube growth. However, the role of canonical Rab5 GTPases that are responsible for two other vacuolar trafficking routes in Arabidopsis pollen tubes is obscure. By using genomic editing, confocal microscopy, pollen tube growth assays, and transmission electron microscopy, we demonstrate that functional loss of canonical Rab5s in Arabidopsis, RHA1 and ARA7, causes the failure of pollen tubes to grow through style and thus impairs male transmission. Functional loss of canonical Rab5s compromises vacuolar trafficking of tonoplast proteins, vacuolar biogenesis, and turgor regulation. However, rha1;ara7 pollen tubes are comparable to those of wild-type in growing through narrow passages by microfluidic assays. We demonstrate that functional loss of canonical Rab5s compromises endocytic and secretory trafficking at the plasma membrane (PM), whereas the targeting of PM-associated ATPases is largely unaffected. Despite that, rha1;ara7 pollen tubes contain a reduced cytosolic pH and disrupted actin microfilaments, correlating with the mis-targeting of vacuolar ATPases (VHA). These results imply a key role of vacuoles in maintaining cytoplasmic proton homeostasis and in pollen tube penetrative growth through style.
Topics: Arabidopsis; Pollen Tube; Arabidopsis Proteins; GTP Phosphohydrolases; Adenosine Triphosphatases
PubMed: 37301984
DOI: 10.1111/nph.19059 -
Frontiers in Plant Science 2019Wheat sheds tricellular short-lived pollen at maturity. The identification of viable pollen required for high seed set is important for breeders and conservators. The...
Wheat sheds tricellular short-lived pollen at maturity. The identification of viable pollen required for high seed set is important for breeders and conservators. The present study aims to evaluate and improve pollen viability tests and to identify factors influencing viability of pollen. In fresh wheat pollen, sucrose was the most abundant soluble sugar (90%). Raffinose was present in minor amounts. However, the analyses of pollen tube growth on 112 liquid and 45 solid media revealed that solid medium with 594 mM raffinose, 0.81 mM HBO, 2.04 mM CaCl at pH5.8 showed highest pollen germination. Partly or complete substitution of raffinose by sucrose, maltose, or sorbitol reduced germination of the pollen assuming a higher metabolic efficiency or antioxidant activity of raffinose. pollen germination varied between 26 lines (P < 0.001); between winter (15.3 ± 8.5%) and spring types (30.2 ± 13.3%) and was highest for the spring wheat TRI 2443 (50.1 ± 20.0%). Alexander staining failed to discriminate between viable, fresh pollen, and non-viable pollen inactivated by ambient storage for >60 min. Viability of fresh wheat pollen assessed by fluorescein diacetate (FDA) staining and impedance flow (IF) cytometry was 79.2 ± 4.2% and 88.1 ± 2.7%, respectively; and, when non-viable, stored pollen was additionally tested, it correlated at r = 0.54 (P < 0.05) and r = 0.67 (P < 0.001) with germination, respectively. When fresh pollen was used to assess the pollen viability of 19 wheat, 25 rye, 11 barley, and 4 maize lines, correlations were absent and germination was lower for rye (11.7 ± 8.5%), barley (6.8 ± 4.3%), and maize (2.1 ± 1.8%) pollen compared to wheat. Concluding, FDA staining and IF cytometry are used for a range of pollen species, whereas media for pollen germination require specific adaptations; in wheat, a solid medium with raffinose was chosen. On adapted media, the pollen tube growth can be exactly analyzed whereas results achieved by FDA staining and IF cytometry are higher and may overestimate pollen tube growth. Hence, as the exact viability and fertilization potential of a larger pollen batch remains elusive, a combination of pollen viability tests may provide reasonable indications of the ability of pollen to germinate and grow.
PubMed: 32038666
DOI: 10.3389/fpls.2019.01588