Search Results (266)

The utilization of cytoplasmic male sterility (CMS) is essential in hybrid seed production; however, its operational value in eggplant is insufficiently documented under practical conditions. This study compared CMS-based and conventional (non-CMS) hybridization systems with respect to flower production, flower functionality, and hybrid seed production efficiency, quantified as seed and viable seedling output per unit time, in three eggplant cultivars (‘Emi’, ‘Langada’, and ‘Tsakoniki’) in intra- and interspecific crosses. CMS did not affect total flower production or inflorescence architecture, which were primarily genotype-dependent. However, it altered flower opening, resulting in genotype- and position-dependent proportions of semi-opened and closed flowers at anthesis. Despite this effect, sufficient flowers suitable for hybridization remained available across all genotypes. CMS substantially simplified the hybridization process by eliminating emasculation, reducing flower manipulation time by approximately 55%, and increasing crossing rate by nearly twofold. Importantly, CMS did not negatively affect female fertility, as indicated by comparable percentages of successful crosses and high seed germination rates across cytoplasmic backgrounds. Seed production per fruit was moderately but significantly increased in intraspecific crosses, while it remained comparable between CMS and non-CMS systems for the interspecific crosses. As a result, CMS significantly increased hybrid seed output and effective seedling production per unit time in intraspecific crosses, while similar trends were observed in interspecific crosses, with gains ranging from 86% to 184% depending on genotype and pollen parent. Overall, this study demonstrates, from an operational perspective, that CMS enhances the efficiency of eggplant hybrid seed production by reducing labor requirements and increasing output per unit time without compromising reproductive performance. These findings highlight the practical value of CMS as a tool for improving hybrid seed production systems, including applications in both commercial hybrid development and rootstock breeding. 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

Gastrodia elata is a mycoheterotrophic orchid. Three of its forms (G. elata f. glauca, G. elata f. elata, G. elata f. viridis) show distinct reproductive traits, but the cytological basis remains unclear. Using multi-timepoint morphological observation and semi-thin/ultra-thin sectioning, we systematically compared their reproductive processes from gametophyte development to seed maturation. All forms exhibited pollen wall polar differentiation (“well-developed locular side, simplified lateral sides”) following a six-stage program, with f. elata germinating fastest, f. viridis intermediate, and no germination in f. glauca. In the female gametophyte, vesicle clusters and degradation zones suggest the possibility of a two-step “chalazal degradation—micropylar localization” nuclear clearance model. Embryo development rate followed f. elata > f. glauca > f. viridis. Mature seeds stored lipid/protein bodies; f. elata uniquely contained amyloplasts and acicular phytin crystals, with form-specific seed coat traits. This study clarifies cytological differentiation, providing a basis for germplasm identification and conservation. Full article

Date palm (Phoenix dactylifera L.) production relies on the availability of viable and physiologically active pollen during female flowering, making pollen storage an important strategy to overcome flowering asynchrony and ensure effective artificial pollination. In this study, we systematically reviewed and quantitatively synthesized the effects of pollen storage conditions on pollen physiological quality and reproductive performance in date palm. Following PRISMA guidelines, 22 experimental studies were identified in the qualitative synthesis, and comparable quantitative datasets were used for meta-analysis. Acetocarmine staining, the most commonly used method for assessing pollen stainability across studies, was selected as the standardized indicator of pollen stainability. Multilevel random-effects meta-regression models were applied to evaluate temporal deterioration patterns over storage periods of up to 24 months, while standardized forest plot meta-analyses were used to estimate pooled effects after 12 months of storage. The results revealed a strong temperature-dependent decline in pollen physiological quality. Acetocarmine stainability declined by −6.41, −3.10, −2.62, and −2.24% month⁻¹ under ambient, refrigerated, mild freezing, and moderate freezing conditions, respectively, whereas germination declined by −6.77, −1.86, −3.14, −1.09, and −1.05% month⁻¹ under ambient (23–25 °C), refrigerated (4–5 °C), mild freezing (−5 °C), moderate freezing (−20 °C), and deep freezing (−80 °C) conditions, respectively. After 12 months of storage, stainability, germination, and fruit set were significantly reduced relative to fresh pollen. In contrast, pollen storage had no significant effect on final fruit weight, suggesting that pollen deterioration primarily affects fertilization success rather than subsequent fruit development. The available evidence suggests that low-temperature storage represents the most effective strategy for preserving date palm pollen functionality. Refrigerated storage around 4 °C appears to provide a reliable and accessible option for short- to medium-term pollen preservation, whereas freezing conditions may be advantageous for longer storage periods when moisture control and thawing procedures are properly managed. Full article

The SHAGGY-like kinase (SK) gene family regulates diverse developmental and abiotic stress response processes in plants. Although genome-wide analyses of SKs have been conducted in model plants such as Arabidopsis thaliana and rice, their characterization in the economically important crop Brassica rapa remains limited. In this study, we conducted a systematic genome-wide analysis of SK genes in three Brassica species. A total of 18, 16, and 18 SK members were identified in B. rapa, B. nigra, and B. oleracea, respectively, and phylogenetic analysis classified them into four distinct clades. Expression profiling revealed that BrSKβ-1 and BrSKβ-2 were specifically expressed in fertile floral buds, suggesting their critical roles in pollen development. Furthermore, co-expression analysis indicated that both genes were co-expressed with key regulators involved in pollen development, pollen sperm cell differentiation and pollen tube growth. Loss of BrSKβ-2 via CRISPR/Cas9 resulted in 25–65% pollen abnormality and reduced the germination rate of normal-appearing pollen to only 10%, confirming its essential role in male fertility. Together, these findings provide a comprehensive characterization of the SK gene family in Brassica and position BrSKβ-2 as a promising candidate for gene editing-based male sterility systems in B. rapa and related crops. Full article

High-temperature (HT) stress during flowering causes male sterility and yield loss in soybean. MYB transcription factors are key regulators under abiotic stress, yet their function and mechanism in regulating male fertility under HT stress in soybean are not fully understood. In this study, a MYB transcription factor GmMYB21a in soybean was identified. GmMYB21a was induced by HT stress in soybean restorer line and was specifically expressed in pollen. Through overexpression and knockout experiments, we demonstrated that GmMYB21a positively regulated pollen viability and germination under HT stress. Overexpression of GmMYB21a significantly enhanced these traits in restorer line, whereas knockout plants exhibited the opposite effect. Transcriptome sequencing revealed that GmMYB21a overexpression upregulated numerous stress-responsive genes, particularly those involved in flavonoid biosynthesis and sugar metabolism. In addition, molecular experiments confirmed that GmMYB21a bound to the promoter of flavonoid synthesis gene GmCHI2-A and promoted its expression. In summary, our research indicated GmMYB21a enhanced the HT-tolerance of male fertility in soybean restorer line through reactive oxygen species scavenging and flavonoid synthesis. This study aims to elucidate the thermotolerance mechanism in soybean male fertility and identify genetic resources for breeding HT-tolerant restorer lines. Full article

Red clover (Trifolium pratense L.) is a crop used as a forage that possesses an exceptional nutritional profile and digestibility. Unfortunately, this crop has low seed yield. Within the framework of the “Legume Generation” EC-funded project, our team aimed to investigate the role of foliar boron application on pollen viability and pollen tube development, and to assess its overall effect on red clover cultivation. Plants of six commercial diploid red clover cultivars, Nika 11, Sofia 52, AberClaret, Milvus, Global, and S123, were field-grown and boron-treated by spraying with the commercial product “Lebasol”, 11% active water-soluble boron. To reach our purpose, the transcript levels of genes related to flower, pollen, and pollen tube development and boron transport were measured by qRT-PCR; pollen grain viability and count were assessed microscopically. For this research, eight genes were selected: Auxin Response factor (TprARF17); TprAPETALA3; Walls are thin (TprWAT1 and TprWAT2); NIPs genes (Nodulin Intrinsic Protein) TprNIP4;2, TprNIP7;1, TprNIP5;1, and TprNIP6;1. Additionally, total nitrogen content in leaves detached from field-grown boron-treated and untreated plants was assessed and compared with the expression levels of two TprNIP5;1 and TprNIP6;1 transporters. The fresh and dry biomass weight from the first and second cuts was evaluated, as well as the seed collected from the red clover plants. Seed germination percentage and vigor of seedlings were examined in vitro for both boron-treated and untreated groups of two specific cultivars. Collected data confirm that foliar application of boron affects pollen viability and plant development of red clover in the cultivation conditions of South East Europe. Full article

Synthetic auxins are widely used nowadays as plant growth regulators and necessary components of media for micropropagation. Hence, the search for and development of novel auxin-like compounds is an important goal at the intersection of chemistry and biology. In this study, we have suggested alkylphenols as starting materials for the preparation of halogenated phenoxyacetic acids, which are well-known synthetic auxins, to decrease their possible phytotoxicity. Alkylphenoxyacetic acids were obtained with good yields, and their selective halogenation was studied. N-halogensuccinimides and molecular bromine in dioxane were shown as suitable reagents since they allowed for p-halogenophenoxyacetic acids to be synthesized with high yields. We further investigated the auxin-like activity of several obtained compounds. It was estimated that all of them stimulate tobacco Nicotiana tabacum L. pollen germination at concentrations 10⁻⁶–10⁻⁷ M with the maximum effect up to 157%. For the most efficient compounds, the germination of tobacco (Nicotiana tabacum L.) and corn (Zea mays) seeds was studied, as well as seedling growth. The results demonstrate the efficacy of obtained compounds as synthetic auxins, showing that alkylphenols are prospective starting materials for such compounds. Full article

Pollen development is a complex process that is highly sensitive to environmental stresses. Abscisic acid (ABA), a key hormone mediating plant growth and stress responses, has been implicated in the regulation of sexual reproduction, especially pollen development, yet its precise regulatory role remains unclear. This study investigated the effects of exogenous ABA on Arabidopsis thaliana pollen development and function through integrated phenotypic, cytological, and transcriptomic approaches. ABA treatment specifically impaired pollen function by reducing germination rates and inhibiting pollen tube elongation, which resulted in shortened siliques and decreased seed set, without affecting pollen morphology or viability. Transcriptome analysis of mature anthers revealed a transient and time-dependent transcriptional response, with the number of differentially expressed genes (DEGs) peaking at 8 h post-ABA treatment and markedly declining by 22 h. These DEGs were enriched in stress-response pathways (e.g., salt, cold, and dehydration), hormone signaling, and carbohydrate metabolism. Moreover, we identified 25 differentially expressed transcription factors and 16 pollen development and function-related genes, highlighting their key roles in ABA-mediated regulation. In parallel, 146 differentially expressed lncRNAs (DELs) were identified, which formed 144 cis-regulatory pairs with genes involved in ABA response and pollen tube growth, with their predicted targets enriched in pathways such as hormone and MAPK signaling, carbohydrate metabolism and stress response. Trans-regulatory analysis further revealed that these DELs co-expressed with DEGs in modules enriched for stress response, pollen development, and tube growth pathways. Notably, key pollen function genes showed strong co-expression with DELs, indicating that lncRNAs participate in ABA-induced transcriptional reprogramming that shifts metabolic resources from growth to defense, thereby suppressing pollen germination and tube elongation. Together, these findings elucidate a coordinated regulatory network involving mRNAs, lncRNAs and transcription factors roles in modulating ABA responses during pollen/anther development. Full article

In Brassicaceae cross-breeding, asynchronous flowering and geographic separation often cause pollen shortages that severely constrain hybridization. Although pollen cryopreservation offers an effective solution, Brassicaceae pollen is typically short-lived due to its tricellular structure, thin exine, and high desiccation sensitivity, necessitating optimized cryopreservation protocols. In this study, we optimized a pollen cryopreservation protocol for three representatives Brassicaceae species: Brassica rapa L. (Chinese cabbage), Brassica oleracea L. (cabbage), and Barbarea vulgaris R. Br. (European rockcress). An in vitro pollen germination system was optimized to reliably assess pollen viability before and after cryopreservation. Key parameters including pollen collection time, drying duration, freezing procedure, and thawing conditions were systematically evaluated. The optimal protocol comprised: pollen collection at 8:00–10:00, drying at 28 °C and 2% relative humidity for 1 h, precooling at −20 °C for 30 min, storage at −80 °C, and thawing under running tap water (ca. 25 °C). Following 30-day cryopreservation, pollen maintained high germination rates (75.19% for Brassica rapa L., 71.18% for Brassica oleracea L., 80.33% for Barbarea vulgaris) and produced comparable silique development, seed quality, and seed germination rates to those of fresh pollen following pollination. This study established a reliable and efficient cryopreservation system for Brassicaceae pollen that effectively overcomes asynchronous flowering and geographic barriers in hybridization, thereby improving breeding efficiency and facilitating germplasm innovation for Brassicaceae crops. Full article

This study examines the reproductive biology of five widely cultivated apple cultivars in Norway (‘Discovery’, ‘Rubinstep’, ‘Red Aroma’, ‘Elstar’, and ‘Asfari’), when crossed with the main pollenizers (‘Summerred’, ‘Discovery’, ‘Katja’, ‘Rubinstep’, ‘Red Aroma’, ‘Fryd’, and ‘Eden’, and two crab apples ‘Professor Sprenger’ and ‘Dolgo’), as well as under self-pollination and open pollination. The experiment was conducted over two seasons (2022–2023) in Hardanger, a region in Western Norway. Flowering time and overlap, in vitro pollen germination, pollen tube growth within the styles and ovary, embryo sac viability, fertilization success, and fruit set were analyzed as key reproductive parameters. Under broadly comparable climatic conditions across both seasons, the results showed that both mother cultivar and the pollenizer strongly influenced progamic processes and fruit set. Pollen tube growth through the pistil was generally faster and more successful in 2022 for all pollination combinations, resulting in a higher fruit set. The only exception was ‘Elstar’, which exhibited a higher fruit set in 2023. If a single optimal pollenizer were to be selected for each apple cultivar in Western Norway, it would be ‘Red Aroma’ for ‘Discovery’ and ‘Rubinstep’; ‘Rubinstep’ for ‘Red Aroma’ and ‘Elstar’; and ‘Professor Sprenger’ for ‘Asfari’. Based on pollen tube growth in vivo and the fruit set, cultivars ‘Discovery’, ‘Rubinstep’, ‘Red Aroma’, ‘Elstar’, and ‘Asfari’ showed self-incompatibility. Full article

In the process of maize production, extreme meteorological conditions such as drought and high temperature are often the main environmental stress factors affecting pollination efficiency. Previous studies have shown that, under adversity, the germination rate of pollen grains on the filaments of female spikes directly affects the success rate of reproduction and ultimately determines the grain yield. This study focuses on a cysteine protease named ZmPCP. The expression of this protease in maize pollen is significantly higher than in other tissues, and its specific function has not been clearly defined. Its localization in the cell membrane or apoplast was further confirmed by transient transfection experiments and plasmolysis. The interaction between ZmPCP and ZmSNAP33 was verified by yeast two-hybrid technology and a GST pull-down experiment, indicating that ZmPCP may affect pollen germination and stress resistance by regulating vesicle transport. Secondly, by analyzing the pollen germination rate of maize inbred lines B104, ZmPCP-KO and ZmPCP-OE transgenic maize plants, we found that ZmPCP overexpression could significantly enhance pollen viability and pollen tube growth under drought stress. After 1 h of short-term drying treatment, the pollen germination rate of the ZmPCP-OE line was maintained at 44%, which was significantly higher than that of the other lines. In addition, the observation of pollen tube growth showed that ZmPCP overexpression could promote the extension of pollen tubes in the filament. Moreover, a transcriptome sequencing analysis revealed the regulatory effects of ZmPCP on pollen in multiple biological processes, including stress response, carbohydrate metabolism, growth and development, cell wall material metabolism, signal transduction, etc. The involved pathways of these differential genes indicate that ZmPCP enhances pollen drought tolerance and promotes pollen tube growth through a “metabolism signal structure”. In the germination experiment on the seventh day, the germination rate of ZmPCP-OE maize seeds was the lowest, indicating that its overexpression inhibited seed germination. At the same time, ZmPCP-overexpressing Arabidopsis showed a significant advantage in taproot growth under high-concentration ABA stress. ZmPCP provides an important theoretical basis for regulating the pollination process and improving the pollination efficiency of maize varieties through interaction with ZmSNAP33. Full article

Genetic engineering tools have the potential to rapidly and precisely improve the genome of slow-to-breed cacao. We previously developed an efficient protocol for transforming cacao using cotyledonary explants derived from secondary somatic embryos via Agrobacterium tumefaciens. In this study, we demonstrate that our transformation protocol is successful in elite cultivars, INIAPG-038 and Matina 1-6, producing fertile seeds with stable visual marker inheritance regardless of whether the transgenic plants were used as the pollen or ovule donor. Three vectors were used in the transformations, each containing genes for enhanced yellow fluorescent protein (eyfp) and neomycin phosphotransferase II (nptII). Three transgenic INIAPG-038 events and one transgenic Matina 1-6 event were used to evaluate seed fertility and the stability of transgene inheritance in cacao seeds and plants. The T₁ progeny of these four transgenic events were analyzed for YFP expression and transgene presence. YFP expression segregated at a 1:1 ratio in all events when the transgenic plants were crossed with non-transgenic plants, while a 3:1 segregation was observed when transgenic events were crossed with each other. The transgenic plants exhibited a normal phenotype compared to non-transgenic control plants, producing seeds with a 97% germination rate. Full article

Pollen acts as both a gametophyte for plant reproduction and a vital nutrient source for bees. Adult honey bees (Apis mellifera) mix pollen with nectar, enzymes, and microbes to create ‘bee bread’, diverting pollen from plant reproduction and re-appropriating it as larval food. However, the point at which corbicular pollen becomes nonviable is largely unknown. This question is important not only because it explicitly addresses pollen viability while bees pollinate, but also because it informs the food vs. fertilization tradeoff at the center of bee–angiosperm mutualisms. Here, we investigated changes in pollen viability during foraging bouts of honey bees. We observed pollen germination across two plant species: Allium tuberosum and Solidago rigida. Bee-collected pollen was contrasted against fresh pollen directly from floral anthers, de-ionized water-soaked pollen, and sucrose solution-washed pollen (a nectar substitute). The bee-collected pollen exhibited significant reductions in germination for both A. tuberosum and S. rigida pollen, compared to controls and the sucrose solution. Pollen viability, therefore, was greatly reduced while the bees in our study were foraging, suggesting that honey bees render pollen nonviable as they pollinate. These findings reveal why corbicular pollen contributes little to plant fertilization, highlighting the importance of non-corbicular ‘body pollen’. Full article

Sustainable agriculture increasingly relies on biostimulants like protein hydrolysates (PHs) to enhance crop resilience. This study characterized and compared three plant-derived PHs (PH1, PH2, and PH3) from the Malvaceae, Brassicaceae, and Fabaceae families, respectively, under optimal (40 µM Fe³⁺-EDTA) and iron (Fe)-deficient (4 µM Fe³⁺-EDTA) conditions. Initial assays demonstrated that the PHs possessed significant antioxidant capacity and influenced biological activity: PH2 and PH3 promoted pollen germination, while PH1 exhibited a weaker stimulatory effect. In vivo experiments on tomato plants revealed that PH application effectively modulated root architecture and biomass accumulation. Moreover, PH2 and PH3 significantly mitigated Fe deficiency’s impact, by maintaining biomass and preventing chlorosis. Interestingly, while Fe deficiency typically triggers massive root Fe³⁺-chelate reductase activity, PH treatments, particularly PH2, significantly down-regulated this response. This suggests that PHs may improve internal Fe use efficiency or facilitate alternative uptake pathways. Overall, these findings establish a link between the intrinsic bioactive properties of PHs and their biostimulant action, highlighting their potential as innovative tools for improving nutrient use efficiency and crop resilience in sustainable farming systems. Full article