Tapetal Cells Research Articles

The establishment of the anther somatic niche with single-cell sequencing

The anther is the developmental housing of pollen and therefore the male gametes of flowering plants. The meiotic cells from which pollen are derived must differentiate de novo from somatic anther cells and synchronously develop with the rest of the anther. Anthropogenic control over another development has become crucial for global agriculture so as to maintain inbred lines and generate hybrid seeds of many crops. Understanding the genes that underlie the proper differentiation, developmental landmarks, and functions of each anther cell type is thus fundamental to both basic and applied plant sciences. We investigated the development of the somatic niche of the maize (Zea mays) anther using single-cell RNA-seq (scRNA-seq). Extensive background knowledge on the birth then pace and pattern of cell division of the maize anther cell types and published examples of cell-type gene expression from in situ hybridization allowed us to identify the primary cell types within the anther lobe, as well as the connective cells between the four lobes. We established the developmental trajectories of somatic cell types from pre-meiosis to post-meiosis, identified putative marker genes for the somatic cell types that previously lacked any known specific functions, and addressed the possibility that tapetal cells sequentially differentiate. This comprehensive scRNA-seq dataset of the somatic niche of the maize anther will serve as a baseline for future analyses investigating male-sterile genotypes and the impact of environmental conditions on male fertility in flowering plants.

Ultrastructural study of pollen and tapetum development in Hydrocleys nymphoides, Alisma plantago-aquatica, and Sagittaria montevidensis (Alismataceae).

The Alismataceae family, widely distributed across tropical temperate swamps and wetlands, includes 15 genera post-merger with Limnocharitaceae. In Argentina, six genera are represented across three clades. Embryological characters, notably the male gametophyte and anther, are crucial in taxonomy due to their stability against environmental changes. This study aims to analyze the ultrastructure of the tapetum and pollen grain development in three economically and ecologically important species representing each clade: Sagittaria montevidensis (Clade A), Hydrocleys nymphoides (Clade B), and Alisma plantago-aquatica (Clade C). Anthers at different developmental stages were processed according to classic techniques for their observation with bright-field and transmission electron microscopy. The three studied species within the Alismataceae family exhibit similar reproductive characteristics. Seven stages of pollen grain development were identified. The microsporogenesis is successive with a regular meiosis. The ultrastructure of the tapetal cells shows similarities to other species with plasmodial tapetum. During the microspore tetrad stage, there is tapetal hyperactivity and an increase in secretion processes. In the free microspore stage, the tapetal cells lose their walls and increase the amount of rough endoplasmic reticulum forming a network of cisternae that extend into evaginations. Later cells completely invade the anther locule and fuse to form a tapetal plasmodium. No peritapetal membrane with orbicules was observed. Pollen is released at the tricellular stage. The pollen grain wall presents an ectexine with a basal layer, columellae, and tectum with supratectal spines while an endexine is not observed in any of the three species. This research enhances the understanding of tapetal cell interactions with developing pollen grains and contributes to the knowledge of the ultrastructure of plasmodial tapetum. Moreover, these findings highlight evolutionary reproductive patterns in Alismataceae, suggesting the plasmodial tapetum as a synapomorphy for the order.

Temperature change regulates pollen fertility of a PTGMS rice line PA64S by modulating the ROS homeostasis and PCD within the tapetum.

Photoperiod and temperature-sensitive male sterility rice is an important line for two-line hybrid rice, and the changes in the cultivation temperature strictly control its pollen fertility. However, the mechanism by which temperature variation regulates pollen fertility is still unclear. This study obtained stable fertile PA64S(F) and sterile PA64S(S) rice from PA64S by controlling temperature changes. PA64S(F) shows a normal anther development and fertile pollen under low temperature (21°C), and PA64S(S) shows delayed degradation of the tapetum cells, leading to abnormal pollen wall formation and ubisch development under normal temperature (28°C). The accumulation of reactive oxygen species (ROS) positively correlates with the programmed cell death (PCD) process of tapetum cells. The delayed accumulation of ROS in the PA64S(S) tapetum at early stages leads to a delayed initiation of the PCD process. Importantly, we localized ascorbic acid (ASA) accumulation in the tapetum cells and determined that ASA is a major antioxidant for ROS homeostasis. ROS-inhibited accumulation plants (PA64S-ASA) demonstrated pollen sterility, higher ASA and lower ROS accumulation in the tapetum, and the absence of PCD processes in the tapetum cell. Abnormal changes in the tapetum of PA64S(S) rice disrupted metabolic pathways such as lipid metabolism, cutin and wax synthesis, sugar accumulation, and phenylpropane, affecting pollen wall formation and substance accumulation, suggesting that the timely accumulation of ROS is critical for male fertility. This study highlights the central role of ROS homeostasis in fertility alteration and also provides an avenue to address the effect of environmental temperature changes on pollen fertility in rice.

OsSNDP4, a Sec14-nodulin Domain Protein, is Required for Pollen Development in Rice

Pollen is encased in a robust wall that shields the male gametophyte from various stresses and aids in pollination. The pollen wall consists of gametophyte-derived intine and sporophyte-derived exine. The exine is mainly composed of sporopollenin, which is biopolymers of aliphatic lipids and phenolics. The process of exine formation has been the subject of extensive research, yet the underlying molecular mechanisms remain elusive. In this study, we identified a rice mutant of the OsSNDP4 gene that is impaired in pollen development. We demonstrated that OsSNDP4, a putative Sec14-nodulin domain protein, exhibits a preference for binding to phosphatidylinositol (3)-phosphate [PI(3)P], a lipid primarily found in endosomal and vacuolar membranes. The OsSNDP4 protein was detected in association with the endoplasmic reticulum (ER), vacuolar membranes, and the nucleus. OsSNDP4 expression was detected in all tested organs but was notably higher in anthers during exine development. Loss of OsSNDP4 function led to abnormal vacuole dynamics, inhibition in Ubisch body development, and premature degradation of cellular contents and organelles in the tapetal cells. Microspores from the ossndp4 mutant plant displayed abnormal exine formation, abnormal vacuole enlargement, and ultimately, pollen abortion. RNA-seq assay revealed that genes involved in the biosynthesis of fatty acid and secondary metabolites, the biosynthesis of lipid polymers, and exosome formation were enriched among the down-regulated genes in the mutant anthers, which correlated with the morphological defects observed in the mutant anthers. Base on these findings, we propose that OsSNDP4 regulates pollen development by binding to PI(3)P and influencing the dynamics of membrane systems. The involvement of membrane systems in the regulation of sporopollenin biosynthesis, Ubisch body formation, and exine formation provides a novel mechanism regulating pollen wall development.

SlHB8 Is a Novel Factor in Enhancing Cold Resistance in Tomato Anthers by Modulating Tapetal Cell Death.

Tomato plants favor warmth, making them particularly susceptible to cold conditions, especially their reproductive development. Therefore, understanding how pollen reacts to cold stress is vital for selecting and improving cold-resistant tomato varieties. The programmed cell death (PCD) in the tapetum is particularly susceptible to cold temperatures which could hinder the degradation of the tapetal layer in the anthers, thus affecting pollen development. However, it is not clear yet how genes integral to tapetal degradation respond to cold stress. Here, we report that SlHB8, working upstream of the conserved genetic module DYT1-TDF1-AMS-MYB80, is crucial for regulating cold tolerance in tomato anthers. SlHB8 expression increases in the tapetum when exposed to low temperatures. CRISPR/Cas9-generated SlHB8-knockout mutants exhibit improved pollen cold tolerance due to the reduced temperature sensitivity of the tapetum. SlHB8 directly upregulates SlDYT1 and SlMYB80 by binding to their promoters. In normal anthers, cold treatment boosts SlHB8 levels, which then elevates the expression of genes like SlDYT1, SlTDF1, SlAMS, and SlMYB80; however, slhb8 mutants do not show this gene activation during cold stress, leading to a complete blockage of delayed tapetal programmed cell death (PCD). Furthermore, we found that SlHB8 can interact with both SlTDF1 and SlMYB80, suggesting the possibility that SlHB8 might regulate tapetal PCD at the protein level. This study sheds light on molecular mechanisms of anther adaptation to temperature fluctuations.

Callose Deficiency Modulates Plasmodesmata Frequency and Extracellular Distance in Rice Pollen Mother and Tapetal cells.

Fertilization relies on pollen mother cells able to transit from mitosis to meiosis to supply gametes. This process involves remarkable changes at the molecular, cellular and physiological levels including (but not limited to) remodelling of the cell wall. During the meiosis onset, cellulose content at the pollen mother cell walls gradually declines with the concurrent deposition of the polysaccharide callose in anther locules. We aim to understand the biological significance of cellulose-to-callose turnover in pollen mother cells walls using electron microscopic analyses of rice flowers. Our observations indicate that in wild type rice anthers, the mitosis-to-meiosis transition coincides with a gradual reduction in the number of cytoplasmic connections called plasmodesmata. A mutant in the Oryza sativa callose synthase GSL5 (Osgsl5-3), impaired in callose accumulation in premeiotic and meiotic anthers, displayed a greater reduction in plasmodesmata frequency among pollen mother cells and tapetal cells suggesting a role for callose in plasmodesmata maintenance. In addition, a significant increase in extracellular distance between pollen mother cells and impaired premeiotic cell shaping was observed in the Osgsl5-3 mutant. The results suggest that callose-to-cellulose turnover during mitosis-meiosis transition is necessary to maintain cell-to-cell connections and optimal extracellular distance among the central anther locular cells. Findings of this study contribute to our understanding of the regulatory influence of callose metabolism during meiosis initiation in flowering plants.

Histochemical and ultrastructural analysis of tapetum and sporoderm development in relation to precocious pollenkitt production of Garcinia dulcis (Roxb.) Kurz.

Garcinia dulcis (Roxb.) Kurz (Clusiaceae) is a medicinal plant native to Southeastern Asia, with a peculiar, precocious pollenkitt production in early microspore development. We aimed to find out whether different secretory activities of the tapetum or a premature sporoderm development provides additional evidence for our recent hypothesis for the precocious pollenkitt production. Histology, histochemistry and ultrastructure of tapetum and sporoderm development during pollenkitt secretion in Garcinia dulcis were conducted, based on light and electron microscopy analysis. The results showed that Garcinia dulcis possesses normal pollen development. The presence of two different pollen coating types, precocious pollenkitt (L1) and common pollenkitt (L2), in the anther tapetum indicate that they are produced in two different active stages of the secretory tapetum. The precocious pollenkitt production and transport to the locule takes place in early active tapetal cells at early tetrad to early microspore stage and is ongoing until late microspore stage. The production of the second type of pollenkitt (L2) starts shortly after the first active tapetum stage together with the formation of sporopollenin precursors. The sporoderm formation was completed at late microspore stage, when the tapetal cell walls start to disintegrate. Orbicules are lining the inner tapetum wall at middle to late microspore stage. ER (during early microspore stage) and plastids (during late microspore stage) were the two main sources of pollenkitt, which finally fused to pollenkitt droplets when the tapetal cells degenerated at mature bicellular pollen stage.

Abnormal Degraded Tapetum1 (ADT1) is required for tapetal cell death and pollen development in rice.

The timely degradation of tapetum, the innermost somatic anther cell layer in flowering plants, is critical for pollen development. Although several genes involved in tapetum development have been characterized, the molecular mechanisms underlying tapetum degeneration remain elusive. Here, we showed that mutation in Abnormal Degraded Tapetum1 (ADT1)resulted in overaccumulation of Reactive Oxygen Species (ROS) and abnormal anther development, causing earlier tapetum Programmed Cell Death (PCD) and pollen abortion. ADT1 encodes a nuclear membrane localized protein, which is strongly expressed in the developing microspores and tapetal cells during early anther development. Moreover, ADT1 could interact with metallothionein MT2b, which was related to ROS scavenging and cell death regulation. These findings indicate that ADT1 is required for proper timing of tapetum PCD by regulating ROS homeostasis, expanding our understanding of the regulatory network of male reproductive development in rice.

AtHMGB15 regulates tapetal apoptosis in pollen development and actin dynamics during pollen germination in arabidopsis.

ARID-HMG DNA binding protein, AtHMGB15, regulates pollen development and pollen germination in Arabidopsis. Previous studies have shown that ARID-HMG DNA binding protein, AtHMGB15 regulate pollen development and pollen germination in Arabidopsis. Here, we performed transcriptome and cytological studies to understand the role of AtHMGB15 in regulating pollen wall morphology and the pollen tube germination rate. Our result showed abnormal vacuolization in the tapetal cells during anther maturation and prolonged PCD in AtHMGB15 loss-of-function mutant. The tapetum has the ability to perform both secretory and biosynthetic activities critical for pollen maturation and pollen viability. Interestingly, expression of PCD executer genes CEP1, MC9 and RNS3 were significant down-regulation of in athmgb15-4. The growth of pollen tubes is regulated by the actin cytoskeleton dynamics. To address the defect in pollen tube growth of athmgb15, we monitored the actin network in growing pollen tubes of wildtype and athmgb15-4 using Rhodamine-phalloidin fluorescence. Our results indicate a highly fragmented actin distribution in athmgb15-4 pollen tubes with a lesser number of long actin fibers and significantly low f-actin concentration at the apex. q-RTPCR further indicates significant downy-regulation of actin regulatory proteins VLN2 and PRF4. Collectively, our results suggest that AtHMGB15 being a nuclear architectural protein orchestrates high-order chromatin organization to promote the transcription of genes responsible for pollen development and pollen germination.

Integrated transcriptomic and metabolomic analysis provides insight into the pollen development of CMS-D1 rice

BackgroundCytoplasmic male sterility (CMS) has greatly improved the utilization of heterosis in crops due to the absence of functional male gametophyte. The newly developed sporophytic D1 type CMS (CMS-D1) rice exhibits unique characteristics compared to the well-known sporophytic CMS-WA line, making it a valuable resource for rice breeding.ResultsIn this research, a novel CMS-D1 line named Xingye A (XYA) was established, characterized by small, transparent, and shriveled anthers. Histological and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assays conducted on anthers from XYA and its maintainer line XYB revealed that male sterility in XYA is a result of delayed degradation of tapetal cells and abnormal programmed cell death (PCD) of microspores. Transcriptome analysis of young panicles revealed that differentially expressed genes (DEGs) in XYA, compared to XYB, were significantly enriched in processes related to chromatin structure and nucleosomes during the microspore mother cell (MMC) stage. Conversely, processes associated with sporopollenin biosynthesis, pollen exine formation, chitinase activity, and pollen wall assembly were enriched during the meiosis stage. Metabolome analysis identified 176 specific differentially accumulated metabolites (DAMs) during the meiosis stage, enriched in pathways such as α-linoleic acid metabolism, flavone and flavonol biosynthesis, and linolenic acid metabolism. Integration of transcriptomic and metabolomic data underscored the jasmonic acid (JA) biosynthesis pathway was significant enriched in XYA during the meiosis stage compared to XYB. Furthermore, levels of JA, MeJA, OPC4, OPDA, and JA-Ile were all higher in XYA than in XYB at the meiosis stage.ConclusionsThese findings emphasize the involvement of the JA biosynthetic pathway in pollen development in the CMS-D1 line, providing a foundation for further exploration of the molecular mechanisms involved in CMS-D1 sterility.

Analysis of the cytohistological phenotype of anthers in sunflower with ASI-AG3 in the context of the PET1 mytotype and the allelic genotype for the Rf1 gene

Microsporogenesis and male gametogenesis are processes that, although under tight morphogenetic control, can often be affected by deviations of internal or external stimuli causing androsterility. The article examines the cytohistological phenotypes of sunflower anthers with gibberellin induced androsterility in plants with different mitotype and allelic genotype for the Rf1 gene, in comparison with the cytohistological phenotypes of fertile and sterile anthers (ASC-PET1). The treatment with gibberellic acid (AG3, 0.01%) was carried out by spraying the inflorescence at the budding stage. Cytological samples and those with semi-thin anther sections were analysed by light microscopy. It was determined that the gametocidal effects induced by AG3 associated with degenerative and early apoptotic events in tapetum cells were more severe in plants with sterile cytoplasm and nuclear Rf1 genes compared to those with fertile cytoplasm and no fertility-restoring genes. In plants with ASC, the exogenous gibberellin stimulus does not cause any visible compensatory events of the sterile phenotype, on the contrary, the effects of microsporogenesis inhibition are more temporally advanced, with sporogenous and sporophytic tissue cells showing various lesions in the premeiosis. The general common and differentiation characteristics found at the androsteril phenotypes suggest interactions between orfH522 and Rf1 gene expression products of negative feedback type in untreated plants and positive feedback type in AG3-treated ones. The research is relevant in the context of elucidating the physiological regulatory processes of the sensitivity of male gametophyte development to various stress conditions, which prospectively makes possible regulatory intervention in plants with different androsterility/androfertility control systems.

Notes on Systematics, Cytology and Culture of <i>Paphiopedilum venustum</i> (Lindl.) Pfitz.

This paper presents a short note on systematics and cytology on Paphiopedilum venustum (Lindl.) Pfitz. (= Cypripedium venustum Lindl.) where the chromosomes are found to be 2n = 40 in the tapetal cells. The cultural notes are also given based on the observation made on the plants growing in the National Orchidarium, Shillong.

Sporophytic control of tapetal development and pollen fertility by a mitogen-activated protein kinase cascade in rice.

Tapetum, the innermost layer of the anther wall, provides essential nutrients and materials for pollen development. Timely degradation of anther tapetal cells is a prerequisite for normal pollen development in flowering plants. Tapetal cells facilitate male gametogenesis by providing cellular contents after highly coordinated programmed cell death (PCD). Tapetal development is regulated by a transcriptional network. However, the signaling pathway(s) involved in this process are poorly understood. In this study, we report that a mitogen-activated protein kinase (MAPK) cascade composed of OsYDA1/OsYDA2-OsMKK4-OsMPK6 plays an important role in tapetal development and male gametophyte fertility. Loss of function of this MAPK cascade leads to anther indehiscence, enlarged tapetum, and aborted pollen grains. Tapetal cells in osmkk4 and osmpk6 mutants exhibit an increased presence of lipid body-like structures within the cytoplasm, which is accompanied by a delayed occurrence of PCD. Expression of a constitutively active version of OsMPK6 (CA-OsMPK6) can rescue the pollen defects in osmkk4 mutants, confirming that OsMPK6 functions downstream of OsMKK4 in this pathway. Genetic crosses also demonstrated that the MAPK cascade sporophyticly regulates pollen development. Our study reveals a novel function of rice MAPK cascade in plant male reproductive biology.

MORE FLORET1 controls anther development by negatively regulating key tapetal genes in both diploid and tetraploid rice.

Polyploid hybrid rice (Oryza sativa) has great potential for increasing yields. However, hybrid rice depends on male fertility and its regulation, which is less well studied in polyploid rice than in diploid rice. We previously identified an MYB transcription factor, MORE FLORET1 (MOF1), whose mutation causes male sterility in neo-tetraploid rice. MOF1 expression in anthers peaks at anther Stage 7 (S7) and progressively decreases to low levels at S10. However, it remains unclear how the dynamics of MOF1 expression contribute to male fertility. Here, we carefully examined anther development in both diploid and tetraploid mof1 rice mutants, as well as lines ectopically expressing MOF1 in a temporal manner. MOF1 mutations caused delayed degeneration of the tapetum and middle layer of anthers and aberrant pollen wall organization. Ectopic MOF1 expression at later stages of anther development led to retarded cytoplasmic reorganization of tapetal cells. In both cases, pollen grains were aborted and seed production was abolished, indicating that precise control of MOF1 expression is essential for male reproduction. We demonstrated that 5 key tapetal genes, CYP703A3 (CYTOCHROME P450 HYDROXYLASE 703A3), OsABCG26 (O. sativa ATP BINDING CASSETTE G26), PTC1 (PERSISTENT TAPETAL CELL1), PKS2 (POLYKETIDE SYNTHASE 2), and OsABCG15 (O. sativa ATP BINDING CASSETTE G15), exhibit expression patterns opposite to those of MOF1 and are negatively regulated by MOF1. Moreover, DNA affinity purification sequencing (DAP-seq), luciferase activity assays, and electrophoretic mobility shift assays indicated that MOF1 binds directly to the PKS2 promoter for transcriptional repression. Our results provide a mechanistic basis for the regulation of male reproduction by MOF1 in both diploid and tetraploid rice. This study will facilitate the development of polyploid male sterile lines, which are useful for breeding of polyploid hybrid rice.

Acyl carrier protein OsMTACP2 confers rice cold tolerance at the booting stage.

Low temperatures occurring at the booting stage in rice (Oryza sativa L.) often result in yield loss by impeding male reproductive development. However, the underlying mechanisms by which rice responds to cold at this stage remain largely unknown. Here, we identified MITOCHONDRIAL ACYL CARRIER PROTEIN 2 (OsMTACP2), the encoded protein of which mediates lipid metabolism involved in the cold response at the booting stage. Loss of OsMTACP2 function compromised cold tolerance, hindering anther cuticle and pollen wall development, resulting in abnormal anther morphology, lower pollen fertility, and seed setting. OsMTACP2 was highly expressed in tapetal cells and microspores during anther development, with the encoded protein localizing to both mitochondria and the cytoplasm. Comparative transcriptomic analysis revealed differential expression of genes related to lipid metabolism between the wild type and the Osmtacp2-1 mutant in response to cold. Through a lipidomic analysis, we demonstrated that wax esters, which are the primary lipid components of the anther cuticle and pollen walls, function as cold-responsive lipids. Their levels increased dramatically in the wild type but not in Osmtacp2-1 when exposed to cold. Additionally, mutants of two cold-induced genes of wax ester biosynthesis, ECERIFERUM1 and WAX CRYSTAL-SPARSE LEAF2, showed decreased cold tolerance. These results suggest that OsMTACP2-mediated wax ester biosynthesis is essential for cold tolerance in rice at the booting stage.

Arabidopsis BECLIN1-induced autophagy mediates reprogramming in tapetal programmed cell death by altering the gross cellular homeostasis

In flowering plants, the tapetum degeneration in post-meiotic anther occurs through developmental programmed cell death (dPCD), which is one of the most critical and sensitive steps for the proper development of male gametophytes and fertility. Yet the pathways of dPCD, its regulation, and its interaction with autophagy remain elusive. Here, we report that high-level expression of Arabidopsis autophagy-related gene BECLIN1 (BECN1 or AtATG6) in the tobacco tapetum prior to their dPCD resulted in developmental defects. BECN1 induces severe autophagy and multiple cytoplasm-to-vacuole pathways, which alters tapetal cell reactive oxygen species (ROS)-homeostasis that represses the tapetal dPCD. The transcriptome analysis reveals that BECN1- expression caused major changes in the pathway, resulting in altered cellular homeostasis in the tapetal cell. Moreover, BECN1-mediated autophagy reprograms the execution of tapetal PCD by altering the expression of the key developmental PCD marker genes: SCPL48, CEP1, DMP4, BFN1, MC9, EXI1, and Bcl-2 member BAG5, and BAG6. This study demonstrates that BECN1-mediated autophagy is inhibitory to the dPCD of the tapetum, but the severity of autophagy leads to autophagic death in the later stages. The delayed and altered mode of tapetal degeneration resulted in male sterility.

Morphological study of sexual reproductive disorders in Ligusticum chuanxiong

Chuanxiong Rhizoma is a well-known Sichuan-specific herbal medicine. Its original plant, Ligusticum chuanxiong, has been cultivated asexually for a long time. L. chuanxiong has sexual reproductive disorders, which restricts its germplasm innovation. However, there is little research on the reproductive system of L. chuanxiong. This study is based on a comparative anatomical research approach, using morphological dissection, paraffin sectioning, staining and compression, and combined with scanning electron microscopy technology, to observe and compare the flowers, fruits, and seeds at various stages of reproductive growth of L. chuanxiong and its wild relative L. sinense. The results showed that the meiosis of pollen mother cells is abnormal in L. chuanxiong anthers, and the size and number of microspores are uneven and inconsistent in the tetrad stage. tapetum cells are not completely degenerated during anther development. During the pollen ripening stage, there are fine cracks in the anther wall, while most anthers could not release pollen normally. The surface of mature pollen grains is concave and partially deformed, and the pollens are all inactive and cannot germinate in vitro. The starch, polysaccharides, and lipids in the pollen were insufficient. The filaments of L. chuanxiong are short at the flowering stage and recurved downward. Double-hanging fruits were observed in the fruiting stage, being wrinkled; with shriveled seeds. Compared with L. sinense at the same stage, the anthers of L. sinense developed normally, and the pollen grains are vigorous and can germinate in vitro. The double-hanging fruits of L. sinense are full and normal; at the flowering period, the filaments are long and erect, significantly higher than the stigma. Mature blastocysts are visible in the ovary of both L. chuanxiong and L. sinense, and there is no significant difference in stigmas. The conclusion is that during the development of L. chuanxiong stamens, the meiosis of pollen mother cells is abnormal, and tetrad, tapetum, filament and other pollen structures develop abnormally. L. chuanxiong has the characteristic of male infertility, which is an important reason for its sexual reproductive disorders.

Сравнительная характеристика кариометрических параметров микроспороцитов и клеток тапетума сформированных пыльников длинно- и короткостолбчатых растений Jasminum fruticans L. (Oleaceae)

In connection with the study of the functional activity of generative structures in heterostylous plants, a comparative karyometric analysis of tapetum cells, as well as microsporocytes of the formed anthers of long-styled and short-styled plants Jasminum fruticans L. (Oleaceae) was carried out. Based on the measurement of the nucleus areas, nucleolus, counting the number of nuclei and nucleoli in cells, the total values of the areas of nuclear structures were calculated. Since the processes of transcription and transformation of ribosomal RNA (r-RNA) are associated with nucleoli, the state of nucleolar structures in a cell reflects the level of its functional activity, therefore, the value of the nuclear-nucleolar ratio (NNR) was used as a characteristic of the functional activity of cells. It was found that in both floral forms, binuclear tapetal cells predominate. The number of nucleoli per cell varies from 1 to 14. The number of tapetal cells with 6-8 nucleoli is greater in short-styled plants than in long-styled plants. However, the cells of tapetum of long-styled and short-styled plants do not have a statistically significant difference of the value of NNR. Comparison of karyometric parameters of microsporocytes showed that the areas of their nuclear structures are larger in long-styled plants, while they are characterized by a higher value of NNR (17.61±0.36) compared with short-styled plants (15.59±0.27). A decrease in the value of NNR in short-styled plants is a sign of an increase in the intensity of protein metabolism of their microsporocytes, and, consequently, the level of functional activity of their genomes. Differences in the functional activity of microsporocytes of long-styled and short-styled plants can be considered as a sign of sex manifestation of sex depending on the floral type of the plant.

Occurrence of parietal and invasive tapetum in Dyckia strehliana (Bromeliaceae): first report for the Family

Abstract Tapetal tissue plays essential roles in the formation of generative cells, as it is related to their nutrition and development in anthers. Among the few species of Bromeliaceae for which tapetal tissue has been describe, most have a secretory tapetum and one has an invasive tapetum. This study analyzed the developmental stages of the anthers of Dyckia strehliana, with emphasis on the tapetum, to identify variability in development and structure. Botanical material was collected on the banks of the Toropi River in the state of Rio Grande do Sul, Brazil, and processed using standard plant micro-techniques. During meiosis prophase, tapetal cells of some samples remained parietal while in the others, a proportional number, the invasion of the locular space begins, culminating in total invasion during the free microspore phase and without fusion of the protoplasts. Tapetal degeneration is complete before gametogenesis begins in both types. Thus, it is possible to describe two modes of development and tapetal structure, one parietal and one invasive, although the tapetum remains as a general secretory type in both cases. Thus, according to present work, the terms invasive and parietal are indicators of states of the secretory tapetum.

Single-Cell Transcriptome Atlas and Regulatory Dynamics in Developing Cotton Anthers.

Plant anthers are composed of different specialized cell types with distinct roles in plant reproduction. High temperature (HT) stress causes male sterility, resulting in crop yield reduction. However, the spatial expression atlas and regulatory dynamics during anther development and in response to HT remain largely unknown. Here, the first single-cell transcriptome atlas and chromatin accessibility survey in cotton anther are established, depicting the specific expression and epigenetic landscape of each type of cell in anthers. The reconstruction of meiotic cells, tapetal cells, and middle layer cell developmental trajectories not only identifies novel expressed genes, but also elucidates the precise degradation period of middle layer and reveals a rapid function transition of tapetal cells during the tetrad stage. By applying HT, heterogeneity in HT response is shown among cells of anthers, with tapetal cells responsible for pollen wall synthesis are most sensitive to HT. Specifically, HT shuts down the chromatin accessibility of genes specifically expressed in the tapetal cells responsible for pollen wall synthesis, such asQUARTET 3 (QRT3) and CYTOCHROME P450 703A2 (CYP703A2), resulting in a silent expression of these genes, ultimately leading to abnormal pollen wall and male sterility. Collectively, this study provides substantial information on anthers and provides clues for heat-tolerant crop creation.