Pollen Tube Growth Research Articles

An involvement of a new zinc finger protein PbrZFP719 into pear self-incompatibility reaction.

This study indicated that the CCHC-type zinc finger protein PbrZFP719 involves into self-incompatibility by affecting the levels of reactive oxygen species and cellulose content at the tips of pollen tubes. S-RNase-based self-incompatibility (SI) facilitates cross-pollination and prevents self-pollination, which in turn increases the costs associated with artificial pollination in fruit crops. Self S-RNase exerts its inhibitory effects on pollen tube growth by altering cell structures and components, including reactive oxygen species (ROS) level and cellulose content. Presently, only a limited number of genes have been implicated in the gametophytic SI. In this study, the CCHC-type zinc finger proteins (ZFP), PbrZFP719, was found to be more highly expressed in pollen grains and pollen tubes than other ZFPs. Experimental over-expression of PbrZFP719 via pollen magnetofection and its knockdown using antisense oligonucleotides demonstrated that PbrZFP719 positively mediates pollen tube growth in pear. Further analyses revealed that variations in PbrZFP719 expression correlate with the changes in ROS levels and cellulose content at the tips of pollen tubes. Notably, PbrZFP719 expression was reduced in pollen tubes treated with self S-RNase. These results suggest that self S-RNase can inhibit pollen tube growth by decreasing ROS levels and cellulose content through the downregulation of PbrZFP719 expression. The information provide insights into a novel mechanism by which self S-RNase inhibits pollen tube growth during SI reaction and offers a refined approach for gene over-expression in pollen tube.

ICE1 (Inducer of CBF Expression 1) Is Essential for the Jasmonate-Regulated Development of Stamen in Arabidopsis thaliana.

Floral organ development, pollen germination and pollen tube growth are crucial for plant sexual reproduction. Phytohormones maintain these processes by regulating the expression and activity of various transcription factors. ICE1, a MYC-like bHLH transcription factor, has been revealed to be involved in cold acclimatisation of Arabidopsis. This study shows that ICE1 regulates multiple aspects of sexual reproduction, including stamen development, pollen development and germination. Loss-of-function mutants of ICE1 exhibit floral organs with shorter filaments, defective anther dehiscence and lower pollen viability compared to the wild type. These abnormalities result in disrupted fertilisation, leading to short siliques, a high rate of seed abortion, and dark, shriveled mature seeds. JAZ proteins (JAZ1 and JAZ9) interact with ICE1, inhibiting its transcriptional activity on jasmonic acid (JA)-responsive genes, including MYB21, MYB24 and MYB108. This study highlights the essential role of ICE1 as a signalling agent in the JA-regulated maintenance of sexual reproduction in Arabidopsis thaliana.

ALBA3 maintains male fertility under heat stress in plants.

Heat stress (HS) at the reproductive stage detrimentally affects crop yields and seed quality. However, the molecular mechanisms that protect reproductive processes in plants under HS remain largely unknown. Here, we report that Acetylation Lowers Binding Affinity 3 (ALBA3) is crucial for safeguarding male fertility against HS in Arabidopsis. ALBA3 is highly expressed in pollen, and ALBA3 is localized in the cytoplasm of both sperm and vegetative cells. Mutants lacking functional ALBA3 exhibit hypersensitivity to HS, with reduced silique length and fertility due to defects in pollen germination, pollination, pollen tube growth, and fertilization under HS. ALBA3 binds and stabilizes a subset of messenger RNAs (mRNAs) essential for pollen function, thereby protecting male fertility. Two residues in the Alba domain, K46 and L90, are critical for ALBA3's ability to bind and stabilize mRNAs and are necessary for its proper function. Interestingly, the loss of rice ALBA3 also leads to severe pollen abortion and male sterility under HS, highlighting the conserved role of ALBA3 in protecting male fertility across plant species. This study uncovers a conserved mechanism by which ALBA3 safeguards male fertility during HS by stabilizing specific mRNAs crucial for pollen function.

Investigating Vesicle-Mediated Regulation of Pollen Tube Growth through BFA Inhibition and AS-ODN Targeting of TfRABA4D in Torenia fournieri

Abstract In flowering plants, pollen tube growth is essential for delivering immotile sperm cells during double fertilization, directly influencing seed yield. This process relies on vesicle-mediated trafficking to drive tip growth and maintain fertility. However, investigating pollen tube growth is challenging in non-model plants due to the lack of transgenic tools. Here, we established a method to transiently inhibit vesicle activity in pollen tubes of the wishbone flower (Torenia fournieri), a classic plant for sexual reproduction studies, using brefeldin A (BFA) and antisense oligodeoxynucleotides (AS-ODNs) targeting key genes. BFA broadly disrupted vesicle gradient homeostasis in T. fournieri pollen tubes, leading to widespread changes in cell wall deposition, ROS distribution, and pollen tube morphology. To assess the role of specific genes, we designed AS-ODNs against TfANX, the sole ANXUR homolog in T. fournieri, which successfully penetrated cell membranes and suppressed TfANX expression. This inhibition impaired pollen tube tip growth, causing pollen tube leakage at the shank region and, in some cases, multiple leakages. Similarly, AS-ODN targeting TfRABA4D, a pollen-specific vesicle regulator, induced a bulging phenotype and disrupted pectin deposition and reduced ROS distribution, mirroring BFA effects. These findings elucidate vesicle-mediated regulation in pollen tube tip growth and introduce an accessible method for genetic manipulation in reproductive research of non-model plants.

Pollen tube-expressed RUPO forms a complex with OsMTD2 and OsRALF17 and OsRALF19 peptides in rice (Oryza sativa).

Pollen tubes are crucial for angiosperm plants, as they deliver sperm gametes for the essential process of double fertilization. Understanding the molecular mechanisms behind pollen tube germination and growth is critical; however, these processes remain partially elucidated in monocot cereal crops. Rapid Alkalinization Factor (RALF), a small peptide of about 5kDa, binds to the CrRLK1L receptor and plays a role in various plant physiological processes, including reproduction and tip growth. Recently, we reported that OsRALF17 and OsRALF19 binds to the OsMTD2, pollen specific CrRLK1L member, and regulates pollen tube growth. In this study, we demonstrate that Ruptured Pollen tube (RUPO), another CrRLK1L member, is also a putative receptor for OsRALF17 and OsRALF19, and propose the formation of a receptor complex with OsMTD2. In tobacco epidermal cells, OsMTD2 and RUPO were co-localized at both the plasma membrane (PM) and the nuclear membrane. Additionally, we generated a RUPO-tagged line driven by its native promoter to visualize subcellular localization during pollen tube growth. RUPO localizes a tip-enriched distribution, with intense fluorescence at the tip's PM and cytoplasm in pollen tube. Upon treatment with synthetic OsRALF17M and OsRALF19M peptides, a reduction in the signal near the PM was observed, suggesting a potential response to these peptides. Our data support the role of RUPO as a candidate receptor for OsRALF17 and OsRALF19 in rice pollen tubes, thereby suggesting a novel mechanism for these RALFs in regulating pollen tube function. Additionally, we observed a significant delay in pollen tube burst time upon treatment with synthetic OsRALF17M and synthetic OsRALF19M. We propose that investigating this phenomenon may provide further insights into the specific signaling pathways mediated by these RALFs.

Extracellular AMP Inhibits Pollen Tube Growth in Picea meyeri via Disrupted Calcium Gradient and Disorganized Microfilaments.

Adenosine monophosphate (AMP) is a hydrolysis product of adenosine triphosphate (ATP) and adenosine diphosphate (ADP). In mammalian cells, extracellular AMP functions as a signaling molecule by binding to adenosine A1 receptors, thereby activating various intracellular signaling pathways. However, the role of extracellular AMP in plant cells remains largely unclear, and homologs of A1 receptors have not been identified. Our previous studies have demonstrated that extracellular ATP (eATP) is crucial for the normal germination and growth of Picea meyeri pollen tubes. In the present study, we observed that the exogenous addition of ATP to a pollen culture medium could be degraded into AMP and adenosine. Furthermore, the addition of AMP and adenosine to the culture medium was found to inhibit pollen germination and tube elongation. Notably, the addition of an AMP receptor inhibitor into the culture medium mitigated the inhibitory effects of AMP on pollen tube growth. Through intracellular staining for Ca2+ and microfilaments, we discovered that high concentrations of AMP disrupt the Ca2+ concentration gradient and impair microfilament organization, ultimately resulting in inhibited pollen tube elongation. In conclusion, we propose that extracellular AMP, as a hydrolysis product of eATP, also plays a significant role in regulating P. meyeri pollen germination and tube growth in vitro.

Effects of the sucrose concentrations and incubation periods on in vitro pollen germination and pollen tube growth in three rice cultivars

Effects of the sucrose concentrations and incubation periods on in vitro pollen germination and pollen tube growth in three rice cultivars

The translation initiation factor eIF3M2 upregulates HEAT SHOCK PROTEIN 70 to maintain pollen tube membrane integrity during heat shock.

Pollen germination and pollen tube (PT) growth are extremely sensitive to high temperatures. During heat stress (HS), global translation shuts down and favors the maintenance of the essential cellular proteome for cell viability and protection against protein misfolding. Here, we demonstrate that under normal conditions, the Arabidopsis (Arabidopsis thaliana) eukaryotic translation initiation factor subunit eif3m1/eif3m2 double mutant exhibits poor pollen germination, loss of PT integrity and an increased rate of aborted seeds. Surprisingly, under HS at 37 °C, eif3m1 pollen germination outperformed wild-type Col-0, showing enhanced PT integrity. We established that the improved thermotolerance of the eif3m1 PT was due to increased expression of its putative paralog eIF3M2, which in turn upregulated Heat Shock protein 70 (HSP70) mRNA and protein levels. Indeed, eIF3M2 overexpression upregulated HSP70 expression, whereas eif3m2 knockdown showed reduced HSP70.1 promoter activity and increased in PT burst under HS conditions. Moreover, we show that eIF3M2 coimmunoprecipitates with HSP70 in PTs and directly interacts with cytoplasmic HSP70.1/2/4 and eIF4G in Nicotiana benthamiana pavement cells. Collectively, our data revealed that plants employ the eIF3M2-HSP70 module as a regulator of thermotolerance to maintain PT membrane integrity and improve fertilization and seed set adaptation under high temperatures.

Effects of Biological Factors and Temperature Elevation on Stigmatic Receptivity and Pollen Tube Growth in Diploid and Hexaploid Plum Genotypes [Prunus salicina and Prunus insititia

ABSTRACTPremise of the study. Biological factors and environmental stresses are predominant elements affecting the progamic phase of sexual plant reproduction. Thus, new knowledge is needed to select and develop cultivars adapted to these changes. This work was conducted to evaluate the pollen growth dynamics and the stigmatic receptivity at normal and elevated temperatures, in 12 Tunisian plum genotypes selected based on six different biological factors. Methods. The pistils were hand‐pollinated using their own pollen, and then the dynamics of pollen tube growth and stigma receptivity of Tunisian plum genotypes were surveyed under ambient temperature and under 35 °C. Key results. Results showed that the differences in flower size, geographical origin and drought tolerance did neither affect pollen growth dynamics nor stigma receptivity. However, the polyploidization enlarged the stigmatic receptivity but does not affect the pollen dynamics. Flowering time and wild plantation fasten the pollen growth and enlarge the stigmatic receptivity. We assume that, in particular case, the flowering plants seem to opt for an enlarged stigmatic receptivity and a rapid pollen growth as reproductive strategies to ‘hold on for dear life’. Experiments conducted at 35 °C showed that the temperature elevation accelerates pollen growth dynamics, while it shortens the stigmatic receptivity period. In particular, two accessions: the wild plum ‘Sauvage’ and the late flowering ‘Tasstour Hamra Tardive’ showed faster pollen growth and enlarged stigmatic receptivity, compared to other accessions. Conclusion. The main relevant conclusion of this work resides in the identification of the best adapted Tunisian genotypes that could be selected as pollen sources to extend the pollination period. Especially, accessions presenting a tolerance to high‐temperature deserve serious attention.

The Role of Reactive Oxygen Species in the In Vivo Germination and Growth of Petunia (Petunia hybrida E. Vilm.) Male Gametophyte in the Progamic Phase of Fertilization

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

Transcriptome profiling of foxtail millet (Setaria italica) pollen and anther

Pollen development and germination play a crucial role in the sexual reproduction of plants. This study analysis of transcriptional dynamics of foxtail millet pollen with other tissues and organs (ovule, glume, seedling and root) through RNA-sequencing revealed that a total of 940 genes were up-regulated in foxtail millet pollen. Based on this, we analyzed the genes involved in pollen tube growth of receptor kinases and small peptides, calcium signaling, small G proteins, vesicle transport, cytoskeleton, cell wall correlation, and transcription factors that are up-regulated in pollen. At the same time, we compared the gene expression of foxtail millet pollen and mature anthers, and found that a large number of transcription factors were specific expressed in mature anthers. In addition, we verified the accuracy of the transcriptome data using RT-qPCR. Finally, employed the antisense Oligonucleotide (as-ODN) system found that inhibiting SiPME67 expression would cause abnormal growth of pollen tube subapical. In summary, we preliminarily analyzed the genes that were up-regulated in foxtail millet pollen, which provided a reference for understanding the male sterility mechanism of foxtail millet in the future and theoretical basis for creating new male sterility lines.

Silencing CaPIP5K4-1 leads to decreased male fertility in Capsicum annuum L.

Phosphatidylinositol 4-phosphate 5-kinase gene CaPIP5K4-1 is highly expressed in the pepper anthers. Virus-induced gene silencing of CaPIP5K4-1 leads to reduced male fertility in pepper. The phosphatidylinositol 4-phosphate 5-kinase (PIP5K) is a pivotal enzyme in the phosphatidylinositol signaling pathway, and its crucial involvement in both plant development and stress response has been established. Here, we found that the expression of CaPIP5K4-1 in pepper was significantly higher in the fertile flower buds compared to sterile flower buds. Furthermore, its expression was validated in anthers and pollens by qRT-PCR and RNA-ISH assays, respectively. Its GFP fusion protein was mainly located on the plasma membrane. Silencing CaPIP5K4-1 in fertile pepper accessions resulted in wrinkled pollen grain cell walls, decreased pollen germination efficiency, and inhibited pollen tube growth. The transcription levels of multiple genes in the phosphatidylinositol signaling pathway were also assessed. Five phospholipase C (PLC) genes were downregulated in silenced plants. On the contrary, inositol phosphatase SAC and phosphatase and tensin homolog (PTEN) were upregulated. This study reported the role of CaPIP5K4-1 in pepper male fertility and provided insights into the regulatory mechanisms of PI signaling in pepper.

Mismatch between pollen and pistil size causes asymmetric mechanical reproductive isolation across Phlox species.

Characterizing the mechanisms of reproductive isolation between lineages is key to determining how new species are formed and maintained. In flowering plants, interactions between the reproductive organs of the flower-the pollen and the pistil-serve as the last barrier to reproduction before fertilization. As such, these pollen-pistil interactions are both complex and important for determining a suitable mate. Here, we test whether differences in style length (a part of the pistil) generate a postmating prezygotic mechanical barrier between five species of perennial Phlox wildflowers with geographically overlapping distributions. We perform controlled pairwise reciprocal crosses between three species with long styles and two species with short styles to assess crossing success (seed set). We find that the heterospecific seed set is broadly reduced compared to conspecific cross success and reveal a striking asymmetry in heterospecific crosses between species with different style lengths. To determine the mechanism underlying this asymmetric reproductive isolating barrier, we assess pollen tube growth in vivo and in vitro. We demonstrate that pollen tubes of short-styled species do not grow long enough to reach the ovaries of long-styled species. We find that short-styled species also have smaller pollen and that both within- and between-species pollen diameter is highly correlated with pollen tube length. Our results support the hypothesis that the small pollen of short-styled species lacks resources to grow pollen tubes long enough to access the ovaries of the long-styled species, resulting in an asymmetrical, mechanical barrier to reproduction. Such reproductive isolating mechanisms, combined with additional pollen-pistil incompatibilities, may be particularly important for closely related species in geographic proximity that share pollinators.

Phosphatidic Acid Signaling in Modulating Plant Reproduction and Architecture.

Phosphatidic acid (PA) is an important class of signaling lipids involved in various biological processes in plants. Functional characterization of the mutants of PA's metabolizing enzymes coupled with lipidomics and protein-lipid interaction analyses have revealed that PA signaling is involved in plant response to biotic and abiotic stress. Moreover, PA and its metabolizing enzymes have been found to affect various reproductive steps, including gametogenesis, pollen tube growth, self-incompatibility, haploid embryo formation, embryogenesis, and seed development. They also play a significant role in shaping plant reproductive and root architecture. Recent results have also started to shed light on the multifaceted modes of PA's action, but much remains to be elucidated. Here, we will review the recent findings of PA and its metabolizing enzymes to highlight their effects on plant sexual reproduction and architecture and discuss the possible mechanisms underlying PA's actions in these processes and future directions.

The influence of Pseudomonas syringae pv. aptata on the functional characteristics of the microgametophyte of beetroot varieties with different levels of resistance to bacteriosis

Relevance. An increase in the spread of bacteriosis on beetroot in the conditions of the Moscow region carries an epidemiological danger, which actualizes research on the development of a method-ology for evaluating table beet plants for resistance to bacteriosis in the early stages of ontogenesis. The aim of the research. To identify the nature of the relationship between the reaction of sporophyte and microgametophyte to infection with Pseudomonas syringae pv. aptata (Psa) bacterium of beet-root varieties with different resistance of root crops to bacteriosis.Materials and methods. Objects of research: beetroot plants of the Marusya and Krasny Barhat varietal populations, collection strain Psa 1-21. Using phytopathological methods and methods of gamete breeding, plant resistance was assessed in various variants of infection of sporophyte and gametophyte with suspension and culture filtrate of Psa.Results. The average volume of the affected area of the Psa root crops of the Marusya variety was 3.5 times greater than that of the Krasny Barhat variety (Vp = 53 mm3), which is characterized by alignment and absence of susceptible forms (Vp >300 mm3). The Marusya variety has a wide intrapopulation polymorphism in the stability of root crops and leaves, where most genotypes showed medium or high susceptibility to the pathogen. Both varieties showed an increase of 10-30% relative to the control of pollen viability at high (CFU 12*108 cl/ml) and low (CFU 2.4*108 cl/ml) concentrations of the pathogen. The positive effect of Psaon the growth of pollen tubes was noted: in the Marusya variety, as the concentration increased, the stimulating effect increased, in the Krasny Barhat variety, it gradually decreased. When adding a 2.5-fold diluted Psa culture filtrate, the susceptible Marusya variety showed an increase in pollen viability (by 3%), and the resistant Krasny Barhat variety showed a 24% decrease relative to the control. According to the growth rate of the pollen tube, the 4:6 dilution was also differentiating, where the average length of the tubes of the susceptible variety exceeded the control by 10%, and in the stable variety it was 18% lower than the control variant.Conclusion. An inverse relationship was revealed between the resistance of sporophyte to Psa and changes in the functional parameters of the microgametophyte of beetroot varieties Marusya and Krasny Barhat under the influence of a phytopathogen. The results obtained indicate the prospects for the development of a methodology for the selection of bacteriosis-resistant genotypes of beetroot by the reaction of microgametophyte.

Widening the tool set for breeding superior banana cultivars. Can new techniques of pollen handling and pollination help overcome the lack of recombinant seed in banana breeding?

Pollen tube growth (PTG) monitoring was applied to florets of domesticated bananas and plantains. Observations were made in UV microscopy after Aniline Blue staining specific for callose, a carbohydrate of pollen tubes. It was found that total pollen grain numbers on a stigma and total pollen tubes developing after sufficient time for growing to reach the ovules within a female floret ranged from nil to few. This suggested the standard hand pollination technique, HP, may be insufficient to achieve desired pollination quality and respective fertilization for seed development. Pollen deposition and pollen tube growth was at least ten times larger when applying the newly developed pollen-anther-stigma, PAS, technique of pollination. This PAS technique includes mechanically working wilted anther pieces holding and exposing the pollen into the female stigma. PAS provided the potential for maximum seed formation depending on genetic limitations that may be present. PAS is therefore recommended for use in investigations of reproductive processes, such as sterility and self-incompatibility, and it can help increasing the production of recombinant seeds in planned crosses for breeding and selection.

Effect of UV-B stress on olive (Olea europaea L.) pollen tubes: A study of callose plug deposition and male germ unit integrity.

While UV-B radiation is beneficial to plant growth, it can also cause adverse effects. The pollen tube, a key component of plant reproduction with a tip growth mechanism, is an excellent cellular model for understanding how environmental stressors such as UV-B radiation affect plant cell growth. This research investigated the effect of UV-B on olive pollen both before and after germination. Pollen grains were hydrated and exposed to UV-B radiation for 1h. Pollen tube germination was then evaluated 4 and 24h after exposure. To study the effect of UV-B radiation on developing pollen tubes, pollen was germinated for 4h prior to 1h of UV-B exposure. Pollen tube growth was evaluated by assessing the distribution of cell wall components, the distance between callose plugs and nuclei, and the distance between the male germ unit and the pollen tube tip. We also examined the accumulation of callose synthase. The results showed that UV-B radiation significantly inhibited the growth of pollen tubes, thereby preventing successful fertilization. The effect of UV-B exposure on pollen tube growth was mainly due to the alteration of position of callose plugs and the level of callose synthase in the pollen tube, potentially affecting its growth. In addition, UV-B radiation affected the movement and integrity of the male germ unit, a critical element for successful fertilization. This research sheds light on how UV-B radiation affects the growth of pollen tubes and highlights the need for further research into the effects of UV-B radiation on plant cells and plant reproduction.

AtFH5 recruits and transports the arabinogalactan protein AGP23 to maintain the tip growth of pollen tube

Actin cytoskeleton drives the targeted transport of cell wall components to sustain the tip growth of pollen tubes for double fertilization; however, the underlying mechanism remains largely unknown. Arabidopsis formin 5 (AtFH5), an actin-nucleating protein, localizes at secretory vesicles and mediates actin polymerization-based vesicle trafficking in pollen. Here, we demonstrate that AtFH5 determines the recruitment and transport of cell wall components in AtFH5-labeled vesicles during the tip growth of pollen tubes. Through a screen of interacting proteins of AtFH5, we identify many cell wall-related proteins, with arabinogalactan protein 23 (AGP23) occupying the highest frequency. AtFH5 interacts with AGP23 via its N-terminal extracellular domain (ECD) and jointly regulate the pollen germination and tube growth process. Further observations reveal that AGP23 co-localizes with AtFH5 at moving vesicles, germination sites, and pollen tube tips, suggesting that AGP23 is delivered by AtFH5-labeled vesicles. Deletion of the ECD of AtFH5 interrupts the dynamic localization and cell-wall connection of AGP23 in pollen grains and tubes. Cytological and genetic evidence shows that AGP23 and AtFH5 work in the same pathway to modulate cell wall composition. Together, our data uncover a role of formin in directing the sorting and deposition of cell wall components via secretory vesicle trafficking during pollen germination and tube growth.

Autophagy modulates Arabidopsis male gametophyte fertility and controls actin organization

Autophagy, a crucial mechanism for cellular degradation, is regulated by conserved autophagy-related (ATG) core proteins across species. Impairments in autophagy result in significant developmental and reproductive aberrations in mammals. However, autophagy is thought to be functionally dispensable in Arabidopsis thaliana since most of the ATG mutants lack severe growth and reproductive defects. Here, we challenge this perception by unveiling a role for autophagy in male gametophyte development and fertility in Arabidopsis. A detailed re-assessment of atg5 and atg7 mutants found that reduced autophagy activity in germinated pollen accompanied by partial aberrations in sperm cell biogenesis and pollen tube growth, leading to compromised seed formation. Furthermore, we revealed autophagy modulates the spatial organization of actin filaments via targeted degradation of actin depolymerization factors ADF7 and Profilin2 in pollen grains and tubes through a key receptor, Neighbor of BRCA1 (NBR1). Our findings advance the understanding of the evolutionary conservation and diversification of autophagy in modulating male fertility in plants contrasting to mammals.

Differential effects of pollen nutritional quality on male and female reproductive success within a diverse co‐flowering community

Abstract Pollen protein content has been demonstrated to be an essential nutritional component for bees and thus important in mediating plant–pollinator interactions. However, little is known on the drivers and consequences of among‐species variation in pollen protein content and how this can impact male and female reproductive success across plant species. Among‐species variation in resources allocated to pollen nutrition could further be constrained by life‐history strategies (e.g. survival‐reproduction trade‐offs) or evolutionary history. Here, we surveyed pollen protein content for 29 species within a diverse co‐flowering community and evaluated the effect of pollen protein on male and female reproductive success. We also tested the role of life history (annuals vs. perennials) and phylogeny in mediating differences in resource allocation to pollen nutrition. We found that pollen protein content influences components of male (bee visitor abundance and pollen dispersal) but not female (conspecific pollen deposition and pollen tube growth) reproductive success, suggesting this trait affects plants only via male function. This sex‐specific effect further suggests the potential for sexual conflicts driven by differential investment on this trait. We found no phylogenetic signal on pollen protein content. However, pollen protein content was higher in annual compared to perennial species suggesting survival versus reproduction trade‐offs also contribute to variation in pollen protein at the community level. Our study underscores the importance of understanding the ecological and evolutionary drivers of pollen protein content across plant species. Our results further suggest the existence of sexual conflicts and ecological trade‐offs mediated by differential investment in pollen nutritional quality, with important implications for community assembly and the structure of plant–pollinator interactions. Read the free Plain Language Summary for this article on the Journal blog.