Search Results (87)

The ubiquitin–proteasome system (UPS) is a highly conserved protein degradation pathway in eukaryotic cells. Through precisely controlled proteolysis of key regulatory proteins, the UPS plays a particularly critical role in plant sexual reproduction, where precise spatiotemporal regulation is essential. The UPS governs multiple aspects of plant sexual reproduction, including male and female gametophyte development, pollen–pistil interactions, double fertilization, and post-fertilization embryogenesis and endosperm development. Among UPS components, E3 ubiquitin ligases play a central role by mediating the spatiotemporal degradation of key proteins, while E2 conjugating enzymes and deubiquitinating enzymes also make essential contributions. Through cross-species and cross-stage comparisons, we find that the UPS exhibits conserved regulatory logic—including cell-cycle gating, spatial control of protein accumulation, and signal integration—while also having evolved lineage-specific functional diversification. In this review, we systematically synthesize UPS functions across the reproductive cycle and highlight persistent knowledge gaps, aiming to provide an integrated framework and a reference for future studies investigating the regulatory roles of the UPS in plant sexual reproduction. Full article

The obligate mutualism between Ficus and its pollinating wasps provides a suitable system to investigate these dynamics because it encompasses two contrasting pollination modes: active and passive. Here we compared pollen traits in an actively pollinated fig tree, Ficus citrifolia, and a passively pollinated species, F. obtusiuscula, examining pollen both at anther presentation and after deposition on the bodies of their pollinating wasps. Pollen morphology, hydration-related behavior, cytology, and reserve composition were characterized using scanning electron microscopy (conventional and modified), light and transmission electron microscopy, histochemical assays, and viability tests. Across species, pollen traits at anthesis showed broad overlap in morphology, viability and major reserve classes, indicating that these characteristics are not consistently predicted by pollination mode alone. In both species, pollen was bicellular, harmomegathic and highly viable at presentation, consistent with resilience during transport. The main divergence emerged after pollen transfer to the pollinator. In the actively pollinated species, pollen recovered from wasp thoracic pockets exhibited pronounced intracellular remodeling, including vacuolization, starch depletion, lipid redistribution and localized cytoplasmic degradation. By contrast, pollen of the passively pollinated species retained a comparatively stable cytological organization after transport despite changes in reserve distribution. These results suggest that the more pronounced cytoplasmic reorganization observed in the pollen of the actively pollinated species after deposition on the wasp body may represent a preparatory phase for rapid germination following pollination, reflecting the stronger dependence of larval development on successful flower fertilization in actively pollinated figs. More broadly, our study provides the first comparative account of pollen structural and cytophysiological dynamics on fig-wasp bodies, linking pollen cell biology to pollinator-mediated dispersal and highlighting how different pollination strategies may impose distinct selective pressures on male gametophytes. Full article

Background: Gametophytic self-incompatibility (GSI) controlled by a multi-allelic S-locus, is inferred to have evolved before the spilt of the Rosidae and Asteridae. In Rosaceae, molecular characterisation of the genera Prunus and Malus reveals that different numbers of genes determine GSI specificity. In Prunus, one pistil-expressed (female) gene and one pollen (male) gene encode a series of stylar RNase (S-RNase) alleles and series of S-haplotype-specific F-box (SFB) alleles, respectively, thereby determining the female and male specificity. In contrast, in Malus, GSI specificity is controlled by one pistil gene and multiple pollen genes, known as SFB-brothers (SFBBs), which encode a series of S-RNase and SFBB alleles, respectively, within the S-locus, to determine female and male specificity. Despite these advances, the molecular mechanisms of these two genera remain largely unknown, and it is still uncertain how GSI originated or which factors shape the orientation, evolution, and function of the S-locus. Methods: Therefore, in this study, we applied a holistic integrative approach combining analyses of gene distribution, phylogenetic inference, biogeographic history, selective pressures, co-evolution, and protein interaction networks across three Prunus genomes (P. dulcis, P. persica, and P. avium) to elucidate the evolutionary forces driving sexual diversity and molecular specificity of GSI within the Rosaceae. Results: Our results indicated that rapid diversification of the Prunus S-locus was due to the repeated duplication events in the SFB, SLF, and S-RNase genes producing both functional and non-functional duplicates. Conclusions: In Rosaceae, diversity of S-locus mechanisms is shaped by lineage-specific selection, functional divergence, co-evolution of pistil- and pollen-expressed components, dynamic protein-interaction networks, geological history and climatic change. Full article

Successful fertilization is essential for fruit bearing and yield enhancement, relying on male gametophyte which facilitates sexual reproduction by transferring the sperm cell to the ovule. To accomplish this task, pectate lyase is secreted to lubricate the sperm cell towards the female partner by different strategies. However, the specific impact of strawberry PL in male sterility and achene development remained elusive. Here, we systematically investigated the functions of diploid strawberry Fragaria vesca pectate lyase 1 (FvePL1), determining its localization in the cell wall and membrane. In situ hybridization presented its maximum expression in the anther, particularly the endothecium, connective tissue, and septum. Analysis of RNAi mutants and green fluorescent protein (GFP)-tagged overexpression lines demonstrated that the failure of FvePL1 significantly inhibited the fruit set due to stunted achenes. In addition, the deficiency of FvePL1 expression resulted in a 68.29% reduction in the number of pollen grains, a 73.27% decrease in pollen viability, morphological alterations of exine and intine, impaired pollen tube, and the inability of the sperm nucleus to reach its target due to the delayed and incomplete tapetal degeneration. In addition, the suppression of FvePL1 resulted in a 65.02% increase in survival rate withholding irrigation for 30 days, conferring enhanced drought tolerance by negatively influencing cell wall structure. Therefore, this study identified FvePL1 as a crucial regulator of pollen development, fertilization, and achene maturation and abiotic stress. These findings provide a framework for advancing research on the development of the male gametophyte in strawberry and even yield optimization in Rosaceous crops. Full article

In modern agriculture, heterotic hybrids produced from hybridization of inbred lines, have shown superiority over open-pollinated and pure line varieties due to their morphological homogeneity, synchronized maturity, and yield performance. The worldwide use of heterosis in plant breeding programs has become possible due to the discovery of cytoplasmic male sterility (CMS), a phenomenon that prevents a plant from producing viable pollen. The CMS-Rf genetic systems are commonly used to produce hybrid seeds. Species from primary, secondary, and tertiary gene pools serve as sources of sterility-inducing cytoplasm in different crop plants. In this review, information on the main genetic factors that induce sterility and restore pollen fertility in F₁ hybrids of economically important cereal (rice, sorghum, maize, rye, wheat, pearl millet) and oilseed (sunflower, rapeseeds, mustard) crops are discussed. The genetic data indicate the location of putatively orthologous candidate Rf genes on syntenic chromosomes in evolutionarily related species. The cytological features of male gametophyte development associated with pollen abortion in lines with CMS are highlighted. The problem of heterotic grouping and selecting parental forms based on genetic distance is discussed. The present knowledge on the genetic resources of different cereal and oilseed crops is highly related to the availability of genomic data. Broadening the CMS source pool and the search for new pollen fertility restoration genes are relevant to avoid cytoplasm unification. Knowledge of the cytoembryological features of CMS manifestation in cereals and oilseed crops is of great importance for understanding the genetic control and practical use of this phenomenon. Utilization of wild species’ genetic resources for these purposes and applying modern techniques of the targeted genome and gene changes at the molecular, genomic, cytological and organismal levels are promising. Full article

Southern highbush blueberry (SHB, Vaccinium corymbosum, Ericaceae) enables production in warm, low-chill regions, where breeding success depends on precisely timed pollinations. To support breeding in non-traditional environments, we characterized floral staging, anther wall ontogeny, tubule formation, and pollen development in two SHB cultivars (‘Emerald’, ‘Snowchaser’) grown in commercial orchards. Floral development was divided into seven stages: dormant buds (db), five successive floral-bud stages (botA–botE), and anthesis, based on bud size, corolla exposure and pigmentation, and anther/tubule coloration. Internal events were documented by light, confocal, and scanning electron microscopy. External cues reliably separated stages and tracked male-gametophyte phases: meiosis at botB; callose-encased tetrads at botC; permanent tetrahedral tetrads after callose dissolution at botD; bicellular tetrads from botE to anthesis, released intact via poricidal dehiscence. Anther-wall differentiation followed a consistent sequence and lacked a fibrous, lignified endothecium. We therefore propose a new Ericaceous pattern for blueberry anthers, defined by a transient non-lignified subepidermal stratum. Tubules originated apically as solid outgrowths, hollowed centrifugally to a beveled pore, developed a dorsal supportive zone, and mediated poricidal release of permanent tetrads. No qualitative cultivar differences were detected. The staging framework defines operational windows for pollination, emasculation, and pollen handling in low-chill systems. Full article

Arabinogalactan proteins (AGPs: hydroxyproline-rich glycoproteins) are ubiquitous in plants and play various functions in cases of development and reproduction. In Arabidopsis thaliana some AGPs can work as markers for gametophytic cell differentiation (among others embryological structures they mark generative cell wall and/or plasma membrane, and also sperm cells). However, apart from Arabidopsis, this labeling of generative cell and sperm cells in pollen grains has only been observed in a few flowering plant species belonging to dicotyledons. No such studies are available in monocotyledons. The main aim of our study was to see whether AGPs would be present at the generative cell–vegetative cell interface in different monocotyledons (representatives of Asparagaceae, Amarylidaceae and Liliaceae), and we also wanted to test whether they would be the same AGPs as in dicotyledons. For the study, we selected Gagea lutea (L.) Ker Gawl., Ornithogalum nutans L. and Galanthus nivalis L. species that differ in shape and size of generative cells. Antibodies against arabinogalactan proteins AGPs were used, including JIM8, JIM13, JIM14, MAC207, LM2, LM14, JIM15 and JIM4. The localization of the examined compounds was determined using immunohistochemistry techniques. The key finding was that AGPs (detected with JIM8 and JIM13 antibodies) consistently mark the boundary between the generative cell and the surrounding vegetative cytoplasm, suggesting their association with the generative cell–vegetative cell interface in all species studied. Identifying such molecular markers in male gametophyte may enhance the understanding of gametophytic cell fate, sperm cell identity and the molecular mechanisms underlying fertilization. Such labeling may also be useful in studies on pollen development, species comparisons, or responses to environmental stresses. Full article

Rhodomelaceae is the largest red algae family, with 158 genera and more than 1000 described nominal species. In particular, Acanthophora (Rhodomelaceae) is a red alga with erect thalli that arises from stoloniferous branches or holdfast discs, with cylindrical main axes and spine-like branchlets. The life cycle of members of this genus has been partially described; however, the female gamete (carpogonium) has not been described. Here, we present a complete description of each stage in the life cycle of Acanthophora. Thalli of this species were collected from 27 localities in the Gulf of Mexico between 2021 and 2024 and placed in a 5% formaldehyde solution in seawater. Reproductive structures were measured and characterized under stereo and optical microscopes. A total of 62 thalli were collected, of which 10 were carposporophytes, 12 male gametophytes, 1 female gametophyte, 16 vegetative thalli, and 23 tetrasporophytic thalli. A detailed description of the shape and size of the reproductive structures is presented. We documented carpogonium for the first time. The evidence here presented contributes to the description of the life cycle of the genus Acanthophora, in which structures forgotten in current works are recovered, which is of great help in the comparative phycology of the Rhodomelaceae family and Ceramiales order. Full article

A combination of high potential productivity and ecological stability is essential for current cultivars, which is achievable by breeding. Interspecific/intergeneric hybridization remains a key approach to producing new high-yielding and resistant cultivars. Interspecific reproductive barriers (IRBs) appear in the interaction between the pollen and pistil of interspecific/intergeneric hybrids. The mechanisms underlying these hybridization barriers are to a considerable degree unknown. The pollen–pistil interaction is decisive because the pollen of distantly related plant species either is not recognized by stigma cells or is recognized as foreign, preventing pollen tube (PT) germination and/or penetration into the stigma/style/ovary. This review mainly focuses on (1) the pollen–pistil system; (2) IRB classification; (3) similarity and differences in the function of self-incompatibility (SI) barriers and IRBs; and (4) physiological and biochemical control of IRBs and their overcoming. The main goal is to illuminate the physiological, biochemical, and molecular mechanisms underlying the growth arrest of incompatible PTs and their death. In general, this review consolidates the current understanding of the interaction of the male gametophyte with the sporophyte tissues of the pistil and outlines future research directions in the area of plant reproductive biology. Full article

Pollen, the male gametophyte of flowering plants, is collected by honeybees as a primary source of protein and converted into bee pollen through the enzymatic activity of digestive secretions. The nutrients in bee pollen are available in amounts well beyond those of proteins, comprising macronutrients such as carbohydrates, lipids and dietary fiber, as well as micronutrients such as minerals, vitamins, organic acids, and phenolic compounds. This study aimed to determine the macro and trace mineral content of bee pollen from different botanical and geographical origins, and to assess their bioaccessibility through simulated in vitro digestion, their dietary contribution, and potential health risks. Seven bee pollen samples were investigated, three with a monofloral origin of above 80%, from Nigella spp., Helianthus annuus and Castanea sativa, and four with a multifloral origin. Mineral composition revealed potassium as the most abundant element, while iron, manganese, and copper were found at trace levels. Castanea sativa pollen had the highest overall mineral content, whereas Nigella spp. showed the lowest values for calcium, magnesium, and copper. The bioaccessibility of bee pollen was highest during the gastric phase for most minerals except copper, where most of the samples peaked in the intestinal phase. Overall, mineral bioaccessibility after simulated digestion followed the order K > Mg > Cu > Ca > Mn > Fe > Zn. While for manganese, the consumption of bee pollen showed the highest contribution to recommended dietary intake (16% for women and 12% for men), calcium had the lowest, with less than 1% of the RDA at a consumption level of 40 g/day. Health risk assessment confirmed that consuming 40 g/day of bee pollen poses no risk because the target hazard quotient and hazard index are below the risk threshold of 1.0. Full article

Cannabis sativa L. is a dioecious species known to produce over 1600 chemical constituents, including more than 180 cannabinoids classified into 11 structural groups. These bioactive compounds are predominantly synthesised in the glandular trichomes of female inflorescences. However, sex determination in C. sativa is influenced by both genetic and environmental factors, often leading to the development of male flowers on female plants. This unintended fertilisation reduces cannabinoid yield and increases genetic heterogeneity and challenges in medical cannabis production. Haploid and doubled haploid (DH) technologies offer a promising solution by rapidly generating homozygous lines from gametophytic (e.g., unpollinated ovaries and ovules) or sporophytic tissues (e.g., anthers and microspores) via in vitro culture or chromosome reduction during hybridisation. In land plants, the life cycle alternates between a diploid sporophyte and a haploid gametophyte generation, both capable of mitotic division to form multicellular bodies. A single genome regulates this phase transition and encodes the molecular, genetic, and epigenetic mechanisms that precisely control the developmental processes unique to each generation. While the application of haploid technology in C. sativa remains limited, through recent progress in haploid induction (HI) and CRISPR-based genome editing, the direct modification of haploid gametes or embryos enables the creation of null homozygous lines following chromosome doubling, improving genetic uniformity. Understanding the molecular mechanisms of spontaneous chromosome doubling may further facilitate the development of elite cannabis genotypes. Ultimately, enhancing the efficiency of DH production and optimising genome editing approaches could significantly increase the speed of genetic improvement and cultivar development in Cannabis sativa. Full article

The efficacy of sweet cherry production is highly dependent on the regularity of flowering events and genetic-determined relations between female sporophyte and male gametophyte, which became even more important with higher flowering temperatures caused by climate change. Special attention is paid to the genetic diversity that provides essential sources of potential temperature-tolerance genes. Our study aimed at the genetic and reproductive characterization of Balkan cherry cultivars of autochthonous origin (‘Canetova’, ‘G-2’, ‘Dolga Šiška’ and ‘Ohridska Crna’), and six potential pollenizers. To identify S-haplotypes, the polymerase chain reaction (PCR) method was used to detect the S-ribonuclease (S-RNase) and S-haplotype-specific F-box protein (SFB) alleles, combined with fragment analysis and S-RNase sequencing. Pollination experiments were performed at three Balkan localities over two flowering seasons, and the fluorescence microscopy method was used to assess the cultivars’ male/female reproductive behaviour. A novel S-RNase allele S₄₀ was identified in ‘Ohridska Crna’ for the first time. ‘Ohridska Crna’ also demonstrated the best adaptability to higher temperatures regarding primary ovule longevity. This feature makes it desirable from the aspect of breeding new cultivars that can withstand the impacts of climate change. The findings on male-female relations and their temperature dependence open up the possibility for yield prediction and smart horticultural decisions that can be made to guide cherry production. Full article

This study investigated key aspects of the reproductive potential of C. sativa cv. Helena. It focused on the development of male and female gametophytes, embryos, and endosperm formation. The developmental stages of pollen grains, embryo sacs, and their formation were revealed. The anther and development of the male gametophyte were as follows: tetrasporangiate anther, (whose wall is developed by the Dicotyledonous type and consists of the epidermis, fibrous endothecium, two middle layers, and glandular tapetum) and two-celled mature pollen. The ovule and development of the female gametophyte were characterized by an upper unilocular ovary containing two anatropous, crassinucellate, bitegmic ovules. The female gametophyte follows the Polygonum (monosporic) type. The development also includes nuclear endosperm formation and the presence of an embryo sac haustorium. A high pollen and seed viability was estimated. This fact, combined with the normal running of the processes of formation and development of the female gametophyte, embryo-, and endospermogenesis provide high reproductive potential for the studied cultivar of C. sativa. These findings contribute to a better understanding of C. sativa reproductive biology and provide valuable insights for breeding programs aimed at optimizing cultivar selection. Full article

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. Full article

In flowering plants, fertilization is a complex process governed by precise communication between the male and female gametophytes. This review focuses on the roles of various female gametophyte cells—synergid, central, and egg cells—in facilitating pollen tube guidance and ensuring successful fertilization. Synergid cells play a crucial role in attracting the pollen tube, while the central cell influences the direction of pollen tube growth, and the egg cell is responsible for preventing polyspermy, ensuring correct fertilization. The review also examines the role of the pollen tube in this communication, highlighting the mechanisms involved in its growth regulation, including the importance of pollen tube receptors, signal transduction pathways, cell wall dynamics, and ion homeostasis. The Ca²⁺ concentration gradient is identified as a key factor in guiding pollen tube growth toward the ovule. Moreover, the review briefly compares these communication processes in angiosperms with those in non-flowering plants, such as mosses, ferns, and early gymnosperms, providing evolutionary insights into gametophytic signaling. Overall, this review synthesizes the current understanding of male–female gametophyte interactions and outlines future directions for research in plant reproductive biology. Full article