Search Results (176)

The effective pollination period (EPP) is a key factor determining fruit set in sweet cherry, as it depends on the overlap between pollen tube growth and ovule longevity. This study investigated the duration and components of the EPP in three autochthonous cultivars (‘Stonska’, ‘Gomilička’, and ‘Tugarka’) grown in the Mediterranean region of Croatia over two consecutive flowering seasons. The EPP was determined under field conditions using sequential hand pollinations, while stigma receptivity, pollen tube growth, and ovule viability were assessed by fluorescence microscopy. Significant genotypic and seasonal variation in EPP and fruit set was observed. ‘Stonska’ and ‘Gomilička’ exhibited extended EPPs (9 and 11 days) and moderate to high fruit set. In contrast, ‘Tugarka’ showed a considerably shorter EPP (4–5 days) and consistently low fruit set (<10%). Stigma receptivity and pollen tube growth were not limiting factors for fertilization. However, rapid ovule degeneration in ‘Tugarka’, particularly under elevated temperatures during flowering, reduced the overlap between pollen tube arrival and ovule viability. These results indicated that ovule longevity plays a major role in determining fruit set and EPP under Mediterranean conditions. The study highlights genotypic differences in temperature sensitivity and provides insight into the potential impact of rising spring temperatures on sweet cherry production. Full article

Distant hybridization in plants is a powerful tool for broadening genetic diversity and developing new varieties with improved traits. However, crosses between genetically distant species are accompanied by reproductive barriers that prevent successful fertilization. This work investigated pollen–pistil interactions during the progamic phase of fertilization in distant crosses involving four members of the Solanaceae family, using several cross combinations. In all cross combinations, pollen of all species germinated on the stigma, grew through the transmitting tissues of the style and ceased growth at a specific distance from the stigma surface. Our studies have revealed that the arrest of pollen tube growth during distant hybridization exhibits a striking similarity to that observed in the gametophytic S-RNase-based self-incompatibility mechanism of Solanaceae plants. Elucidating the mechanisms of pollen tube growth arrest during distant hybridization in Solanaceae will provide deeper insight into the nature of reproductive barriers and aid in the development of strategies to overcome them, thereby expanding the possibilities for successful hybridization between distant species and enabling the creation of valuable new varieties. Full article

Daddow is a macadamia cultivar that yields poorly because flowers and fruitlets frequently abort early in development. The objective was to determine whether resource availability limits fruitlet retention in this cultivar. Racemes of Daddow and three other cultivars, 849, A38, and A203, were sampled weekly during flowering and fruit set, and trends in nutrients and non-structural carbohydrates were assessed. Starch concentrations in the flowers and rachis were lower in Daddow than in the other cultivars before fruit set. Rachis concentration of glucose, an important signalling molecule, was also lower in Daddow at flowering. Most flower and fruitlet nutrient concentrations in Daddow were comparable to those of the other cultivars. However, potassium concentrations were lower in both the rachis and leaves of Daddow, while boron concentration, important for pollen tube growth, was higher. These results suggest altered signalling mechanisms, inadequate carbohydrate supply and deficiencies in specific nutrients may have been contributing factors to the high flower and fruitlet abortion rates of Daddow. Full article

Amino acids are organic compounds that serve as the fundamental building blocks of proteins and are additionally responsible for a multitude of other biological functions. This review synthesizes recent evidence elucidating that amino acids function as vital players in nitrogen transport, stress defense, and perhaps most intriguingly as signaling molecules. For example, glutamate triggers calcium signals through GLR receptors to guide root growth and pollen tubes. Others, like proline and glutathione, protect cells from drought, salt, and oxidative damage. Aromatic and sulfur-containing amino acids also feed into the production of hormones (auxin, ethylene) and a wide range of defense compounds. Beyond metabolism, we highlighted how plants sense amino acid status via ancient sensors such as PII and the TOR pathway, which fine-tune growth and resource allocation. Understanding this hidden side of amino acids opens new doors for agriculture. We discussed how these insights could lead to smarter biostimulants, gene-edited crops with better nutrient efficiency, and nano-based delivery systems. In short, amino acids are not just food for plants—they are signals, shields, and switches that shape how plants grow and cope with stress. Full article

Self-incompatibility (SI) is an important plant mechanism that prevents inbreeding depression by recognizing and rejecting self-pollen, thereby promoting outcrossing. However, SI can also act as a barrier in breeding programs, presenting significant challenges to breeders. Passion fruit (Passiflora edulis), a tropical fruit species of substantial economic importance, also serves as a valuable system for investigating SI mechanisms within the Passifloraceae. Nevertheless, the molecular basis of SI in passion fruit has not yet been elucidated. In this study, we investigated the SI system in yellow passion fruit (P. edulis f. flavicarpa) and employed transcriptomic analysis to examine the time-course transcriptional responses following different pollination treatments. Transcriptomic analysis revealed distinct gene expression dynamics under different pollination treatments: self-pollinated samples exhibited stronger and earlier transcriptional changes, whereas the number of differentially expressed genes (DEGs) in cross-pollinated samples was relatively lower. Numerous pathways previously associated with sporophytic self-incompatibility (SSI) were enriched in the stigma samples after self-pollination. Reactive oxygen species (ROS) are crucial signaling molecules involved in pollen germination and pollen tube growth during SI responses. Our results showed that ROS-related pathways were enriched in stigma tissues after self-pollination. In addition, oxidative stress-related responses were detected in the style shortly after self-pollination, suggesting that plastid-associated or general oxidative stress processes may also be involved, although the precise source of ROS requires further validation. FERONIA, ROP9, and ARC1 are key genes related to the SI system in Brassica. In the passion fruit SI response, the expression levels of these genes increased in the style, indicating a spatial expression pattern different from that reported in classical Brassicaceae SSI systems. Together with cytological observations showing that self-pollen rejection occurs at the stigma surface, our results suggest that yellow passion fruit may employ an SSI-like regulatory framework while exhibiting a lineage-specific spatial deployment of SI-related regulators. Overall, this study provides new transcriptomic insights into the SI mechanism of yellow passion fruit, establishes a molecular framework for understanding SI in P. edulis f. flavicarpa, and offers novel insights into the diversity of plant SI systems. Full article

Reproductive barriers severely limit interspecific hybridization success among Hydrangea macrophylla, H. paniculata, and H. arborescens, thereby restricting the combination of ornamental traits and cold hardiness. We evaluated cross-compatibility, pollen tube growth, and embryo development in both direct and reciprocal crosses involving H. macrophylla with H. paniculata and H. arborescens. Both species pairs exhibited pronounced unilateral incompatibilities. When H. macrophylla served as the maternal parent, the percentages of seedling emergence were higher, whereas reciprocal crosses produced >84% ovary swelling but resulted in almost no seedlings. Fluorescence microscopy revealed mild prezygotic barriers in direct crosses but strong inhibition of pollen germination and pollen tube growth in reciprocal crosses. Paraffin section observations showed that postzygotic barriers were the primary cause of hybrid failure, with endosperm-type abortion predominating in direct crosses and embryo-type or complete abortion in reciprocal crosses. Consistent with these abortion patterns, direct crosses maintained higher proportions of normal embryos, whereas reciprocal crosses dropped below 10% at the globular stage and approached 0% at later stages. These findings support the use of timely embryo rescue for direct crosses and targeted mitigation of prezygotic barriers in reciprocal crosses to improve Hydrangea interspecific hybridization efficiency. 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

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

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

Self-incompatibility (SI) is a key reproductive mechanism in angiosperms that prevents self-fertilization and promotes genetic diversity while limiting breeding efficiency. Akebia trifoliata is a recently domesticated economic crop native to East Asia with medicinal, edible, and oil-producing value. However, its late-acting self-incompatibility (LSI) severely limits genetic improvement and commercial development. To investigate the molecular basis of LSI, we conducted comparative transcriptomic analyses of pistils at 48, 96, 144, 192, and 240 h after self- and cross-pollination, identifying 1552, 2954, 1302, 814, and 1978 differentially expressed genes (DEGs), respectively. DEGs were consistently enriched in mitogen-activated protein kinase (MAPK) signaling, plant hormone signal transduction, and ubiquitin-mediated proteolysis pathways, with clear transcriptional differences before and after 96 h. Compared with cross-pollinated pistils, self-pollinated pistils showed restricted pollen tube spread, and genes related to pollen recognition and tube development showed differential expression at 48 and 96 h, indicating that LSI probably occurs within the pollen tube. Collectively, these results indicate that pistils of A. trifoliata exhibit distinct early responses to self- and cross-pollination, and that DEG-enriched pathways are similar to those involved in S-RNase-mediated SI. These results provide new insights into the molecular basis of LSI and suggest potential targets for overcoming the SI barrier. 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

Magnolia crassipes is a valuable species in Magnolia sect. Michelia known for its unique purple flowers, but interspecific reproductive barriers limit its use in breeding. Using M. crassipes as the maternal parent, we performed 13 pollination combinations (one selfed control and crosses with 12 taxa spanning five sections). We assessed reproductive processes from pollen–stigma interaction to seed and seedling performance, and verified hybrids using SSR markers. Reproductive barriers are strongly associated with phylogenetic distance, shifting from pollen-adhesion failure in crosses with donors from distant-section, to abnormal pollen-tube guidance in cross with M. denudata, and to fruit initiation in crosses with pollen donors from sect. Michelia. Among these Michelia-donor crosses, prezygotic barrier strength varied among combinations, as reflected by differences in stigma germination and ovule entry rates, which strongly influenced the potential for fruit set success. Postzygotic barriers further reduced reproductive success via seed abortion (peaking at 83.8%). However, all germinated hybrids exhibited normal early growth. Notably, backcrossing with the F1 hybrid M. ‘Danxia’ significantly improved reproductive compatibility (seed abortion rate 6.3% and germination rate 100%). This study clarifies the key barriers in M. crassipes hybridization and provides a basis and practical strategies for its genetic utilization. Full article

During the development of the gametophyte in angiosperms, a series of processes occurs, including pollination, pollen recognition, adhesion, hydration, germination, pollen tube growth, and the guidance of the pollen tube toward the ovule for the delivery of sperm cells to the female gametophyte. These processes require a substantial energy supply, which is provided by cellular respiration in the plant. Throughout this sequence, the generation of reactive oxygen species (ROS) is concomitantly observed. At present, the mechanisms underlying ROS production remain incompletely understood, especially in plant trees such as Salix linearistipularis. In this study, pistils of S. linearistipularis were used as experimental materials, and pistils were divided according to their development into three stages—S1, S2, and S3. Transcriptome sequencing (RNA-Seq) was performed for the three developmental stages, and the results indicated that metabolic pathways associated with oxidoreductase activity were highly significant during pistil development in S. linearistipularis. During pistil development, the levels of ROS accumulated rapidly. After pollination, with the adhesion and germination of pollen, the levels of ROS decreased significantly. Moreover, bidirectional regulation of ROS levels revealed that treatment with ROS inducers and scavengers led to increased and decreased ROS accumulation, which were accompanied by the inhibition and promotion of pollen tube number and length. These two opposite results indicate that ROS are the key factor regulating pistil development and pollen tube germination in S. linearistipularis. Full article

Rapid alkalinization factor (RALF) peptides represent a central class of signaling molecules in plants, regulating processes ranging from fertilization to immune responses. These diverse functions are largely mediated by a conserved receptor complex centered on FERONIA kinase (FER). This review summarizes recent advances positioning the RALF-FER signaling pathway as a major regulatory hub integrating intrinsic and extrinsic signals to coordinate growth, development, and stress adaptation. We examine how this pathway controls the polar growth of root hairs and pollen tubes, orchestrates reproductive barriers and fertilization, and modulates immune and abiotic stress signaling through mechanisms involving ROS, Ca²⁺, and apoplast pH. By framing this new knowledge within the broader framework of known RALF-FER mechanisms, we demonstrate how this pathway achieves high signaling specificity. Finally, we discuss critical unresolved issues and suggest future research directions in the emerging field of molecular stress physiology, highlighting the potential for manipulating this pathway for agricultural crop improvement. Full article

Pollen tube growth entails complex molecular interactions between the cytoskeletal apparatus and membrane trafficking. Tip growth involves polarized distribution of proteins and lipids along the plasma membrane, including liquid-ordered microdomains, rich in sterols and sphingolipids (lipid rafts), in the apical/subapical region of tobacco pollen tubes. Intriguingly, biochemical characterization of detergent-insoluble membranes purified from tobacco pollen tubes revealed the presence of both actin and tubulin. Here, we report that inhibition of sterol biosynthesis altered lipid rafts and lowered the association of tubulin with detergent-insoluble membranes. Our results showed that sterol depletion increased the number of microtubules in the subapical region, altered microtubule distribution and affected microtubule bundling activity. Oryzalin washout experiments also suggested that lipid-ordered domains could play a role in regulating microtubule nucleation/regrowth. Full article