Ovule Development Research Articles

Type II arabinogalactans initiated by hydroxyproline-O-galactosyltransferases play important roles in pollen-pistil interactions.

Arabinogalactan-proteins (AGPs) are hydroxyproline-rich glycoproteins containing a high sugar content and are widely distributed in the plant kingdom. AGPs have long been suggested to play important roles in sexual plant reproduction. The synthesis of their complex carbohydrates is initiated by a family of hydroxyproline galactosyltransferase (Hyp-GALT) enzymes which add the first galactose to Hyp residues in the protein backbone. Eight Hyp-GALT enzymes have been identified so far, and in the present work a mutant affecting five of these enzymes (galt2galt5galt7galt8galt9) was analyzed regarding the reproductive process. The galt25789 mutant presented a low seed set, and reciprocal crosses indicated a significant female gametophytic contribution to this mutant phenotype. Mutant ovules revealed abnormal callose accumulation inside the embryo sac and integument defects at the micropylar region culminating in defects in pollen tube reception. In addition, immunolocalization and biochemical analyses allowed the detection of a reduction in the amount of glucuronic acid in mutant ovary AGPs. Dramatically low amounts of high-molecular-weight Hyp-O-glycosides obtained following size exclusion chromatography of base-hydrolyzed mutant AGPs compared to the wild type indicated the presence of underglycosylated AGPs in the galt25789 mutant, while the monosaccharide composition of these Hyp-O-glycosides displayed no significant changes compared to the wild-type Hyp-O-glycosides. The present work demonstrates the functional importance of the carbohydrate moieties of AGPs in ovule development and pollen-pistil interactions.

KNOX transcription factor VvHB63 affects grape seed development by interacting with protein VvHB06

The fast-growing demand for seedless table grapes has attracted the attention of scientists for the development of new seedless cultivars. Various genes and pathways have been identified which affect seedlessness. However, the detail of the mechanism(s) regulating seedless traits in grape is still unclear, and genes related to seedlessness in grape require further study. Transcriptomic and genomic analyses of Homeobox (HB) transcription factors have suggested the involvement of HB genes, especially of HB-KNOX members, in grape seed development. Here, we functionally characterize VvHB63 gene in grape and report its role in fruit and seed development. VvHB63 showed higher expressions levels in the chalaza and integument of ovules in seedless grapes, than in seeded ones. However, no differences were observed in the sequences of seedless and seeded grape cultivars. In situ hybridization (ISH) analysis showed that VvHB63 gene was expressed in the episperm cells and ovules of 'Thompson Seedless'. Conserved domains KNOX1 and KNOX2 were important for the interaction of VvHB63 with VvHB06. Heterologous over-expression of VvHB63 (35 S::VvHB63-OE) in tomato induced smaller fruits and seeds than in wild type or SlTkn1-KO. The synergistic cooperation between VvHB63 and related proteins play an important role in ovule development.

A model worker: Multifaceted modulation of AUXIN RESPONSE FACTOR3 orchestrates plant reproductive phases.

The key phytohormone auxin is involved in practically every aspect of plant growth and development. Auxin regulates these processes by controlling gene expression through functionally distinct AUXIN RESPONSE FACTORs (ARFs). As a noncanonical ARF, ARF3/ETTIN (ETT) mediates auxin responses to orchestrate multiple developmental processes during the reproductive phase. The arf3 mutation has pleiotropic effects on reproductive development, causing abnormalities in meristem homeostasis, floral determinacy, phyllotaxy, floral organ patterning, gynoecium morphogenesis, ovule development, and self-incompatibility. The importance of ARF3 is also reflected in its precise regulation at the transcriptional, posttranscriptional, translational, and epigenetic levels. Recent studies have shown that ARF3 controls dynamic shoot apical meristem (SAM) maintenance in a non-cell autonomous manner. Here, we summarize the hierarchical regulatory mechanisms by which ARF3 is regulated and the diverse roles of ARF3 regulating developmental processes during the reproductive phase.

Sporogenesis, gametophyte development and embryogenesis in Glehnia littoralis

BackgroundGlehnia littoralis is an economic herb with both medicinal and edible uses. It also has important ecological value and special phylogenetic status as it is a monotypic genus species distributing around beach. Little information on its reproductive biology has been reported so far, which has hindered conservation and application of this species. In this study, we observed morphological changes from buds emergence to seeds formation and internal changes during sporogenesis, gametophyte development and embryo and endosperm development of G. littoralis using paraffin-embedded-sectioning and stereo microscope.ResultsThe results showed that the stages of internal development events of G. littoralis corresponded to obvious external morphological changes, most of developmental features were consistent with other Apiaceae species. The development of male and female gametophytes was not synchronized in the same flower, however, exhibited temporal overlap. From mid-late April to mid-May, the anther primordial and ovule primordial developed into the trinucleate pollen grain and eight-nuclear embryo sac, respectively. From late-May to mid-July, the zygote developed into mature embryo. In addition, some defects in gynoecium or ovule development and abnormal embryo and endosperm development were found. We induced that the possible causes of abortion in G. littoralis were as follows: nutrient limitation, poor pollination and fertilization, and bad weather.ConclusionsThis study revealed the whole process and morphological characteristics of the development of reproductive organ in G. littoralis, which not only provided important data for the study of systematic and conservation biology, but also provided a theoretical basis for cross breeding.

Comparative analysis of the transcriptome during single-seed formation of Castanea henryi: regulation of starch metabolism and endogenous hormones

BackgroundIn seed plants, the ovule is the precursor to the seed. The process of ovule development and differentiation is regulated by multiple factors, including starch metabolism and endogenous hormones. Castanea henryi produces nuts with high nutritional value. However, the high proportion of empty buds restricts the commercial use of the tree. Previous studies have shown that the empty bud phenotype is closely related to ovule abortion. If none of the ovules in the ovary expand rapidly and develop in 7–8 weeks after pollination, an empty bud will form. Therefore, we studied the development and molecular mechanisms underlying single seed formation in C. henryi.ResultsWe found that 49 days after pollination (DAP) is a critical period for the formation of fertile and abortive ovules. The morphology and starch distribution of the fertile and abortive ovules differed significantly at 49 DAP. The fertile ovules were smooth and round in appearance, with a large amount of starch. In contrast, abortive ovules were smaller with only a small amount of starch. The embryo sac of the abortive ovule proceeded to develop abnormally, and the entire ovule lacked starch. We identified 37 candidate genes involved in metabolism with potential roles in the regulation of starch levels. Three ADP-glucose pyrophosphorylase (AGPase) genes, one granule-bound starch synthase (GBSS) gene, and two beta-amylase genes could affect starch accumulation. The levels of auxin, cytokinins, gibberellins, and jasmonic acid in fertile ovules were higher than those in abortive ovules. In addition, the levels of endogenous abscisic acid and salicylic acid in abortive ovules were higher than those in fertile ovules of the same age, consistent with the expression patterns of genes related to the synthesis of abscisic and salicylic acid and signal transduction. We identified and mapped the differentially expressed genes associated with hormone synthesis and signal transduction.ConclusionsThese results improve our general understanding of the molecular mechanisms underlying single seed development in C. henryi and the phenomenon of empty buds, providing directions for future research.

Genomic identification of cotton SAC genes branded ovule and stress-related key genes in Gossypium hirsutum.

SAC genes have been identified to play a variety of biological functions and responses to various stresses. Previously, SAC genes have been recognized in animals and Arabidopsis. For the very first time, we identified 157 SAC genes in eight cotton species including three diploids and five tetraploids with 23 SAC members in G. hirsutum. Evolutionary analysis classified all cotton SAC gene family members into five distinct groups. Cotton SAC genes showed conserved sequence logos and WGD or segmental duplication. Multiple synteny and collinearity analyses revealed gene family expansion and purifying selection pressure during evolution. G. hirsutum SAC genes showed uneven chromosomal distribution, multiple exons/introns, conserved protein motifs, and various growth and stress-related cis-elements. Expression pattern analysis revealed three GhSAC genes (GhSAC3, GhSAC14, and GhSAC20) preferentially expressed in flower, five genes (GhSAC1, GhSAC6, GhSAC9, GhSAC13, and GhSAC18) preferentially expressed in ovule and one gene (GhSAC5) preferentially expressed in fiber. Similarly, abiotic stress treatment verified that GhSAC5 was downregulated under all stresses, GhSAC6 and GhSAC9 were upregulated under NaCl treatment, and GhSAC9 and GhSAC18 were upregulated under PEG and heat treatment respectively. Overall, this study identified key genes related to flower, ovule, and fiber development and important genetic material for breeding cotton under abiotic stress conditions.

Megasporogenesis and Megagametogenesis in Coelogyne speciosa subsp. fimbriata (J.J.Sm.) Gravendeel (Orchidaceae Juss.)

Understanding the critical stages in ovule development is essential for optimizing in vitro seed propagation, cryopreservation, and indirect somatic plant embryogenesis. We studied the main stages of the megasporogenesis and megagametogenesis of Coelogyne speciosa subsp. fimbriata (J.J.Sm.) Gravendeel by confocal laser scanning microscopy. The ovule is anatropic, tenuinucellate, bitegmal, and funicular. The embryo sac is monosporic, Polygonum-type, bipolar, and usually 8-nuclear, but in cases of a reduction in the last mitotic division, it is 6-nuclear. Endosperm formation was not detected. The formation of a functional megaspore occurred 65–70 days after pollination (DAP), while the formation of a mature embryo sac and fertilization occurred after 85–100 DAP.

Ovule cell wall composition is a maternal determinant of grain size in barley.

In cereal species, seed and grain size is influenced by growth of the ovule integuments (seed coat), the spikelet hull (lemma and palea) and the filial endosperm. It has remained unclear whether a highly conserved ovule tissue, the nucellus, has any impact on grain size. Immunolabelling revealed that the barley nucellus comprises two distinct cell types that differ in terms of cell wall homogalacturonan (HG) accumulation. Transcriptional profiling of the nucellus identified two pectin methylesterase genes, OVULE PECTIN MODIFIER 1 (OPM1) and OPM2, which are expressed in the ovule but absent from the seed. Ovules from an opm1 opm2 mutant, and plants expressing an ovule-specific pectin methylesterase inhibitor (PMEI), exhibit reduced HG accumulation. This results in changes to ovule cell size and shape, and ovules that are longer than wild-type controls. At grain maturity, this is manifested as significantly longer grain. These findings indicate that cell wall composition during ovule development acts to limit ovule and seed growth. The investigation of ovule PME and PMEI activity reveals an unexpected role of maternal tissues in controlling grain growth prior to fertilisation, one that has been lacking from models exploring improvements in grain size.

The EPFL-ERf-SERK signaling controls integument development in Arabidopsis.

As the seed precursor, the ovule produces the female gametophyte (or embryo sac), and the subsequent double fertilization occurs in it. The integuments emerge sequentially from the integument primordia at the early stages of ovule development and finally enwrap the embryo sac gradually during gametogenesis, protecting and nursing the embryo sac. However, the mechanisms regulating integument development are still obscure. In this study, we show that SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASES (SERKs) play essential roles during integument development in Arabidopsis thaliana. The serk1/2/3 triple mutant shows arrested integuments and abnormal embryo sacs, similar defects also found in the triple loss-of-function mutants of ERECTA family (ERf) genes. Ovules of serk1/2/3 er erl1/2 show defects similar to er erl1/2 and serk1/2/3. Results of yeast two-hybrid analyses, bimolecular fluorescence complementation (BiFC) analyses, and co-immunoprecipitation assays demonstrated that SERKs interact with ERf, which depends on EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) family small peptides. The sextuple mutant epfl1/2/3/4/5/6 shows integument defects similar to both of er erl1/2 and serk1/2/3. Our results demonstrate that ERf-SERK-mediated EPFL signaling orchestrates the development of the female gametophyte and the surrounding sporophytic integuments.

VvAGAMOUS Affect Development of Four Different Grape Species Ovary

Grape pistil has an important influence on fruit size and quality. However, there were few studies on grape ovary, and the development process of the ovary is still unclear. Therefore, in this paper, four different grape varieties with different lengths of small inflorescences, namely ‘Musct Hambourg’ grape (Vitis vinifera), ‘Concord’ grape (Vitis labrusca), ‘ShanPuTao’ grape (Vitis amurensis) and ‘GongNiang2Hao’ grape (Vitis amurensis × Vitis vinifera) were used as test materials. Four varieties ovary were significant differences by means of stereomicroscope, paraffin section. The expression of ovary determining gene VvAGAMOUS (VvAG) and its development related genes VvCRABS CLAW (VvCRC) and VvAGAMOUS-LIKE 11 (VvAGL11) with similar functions during the development of different grape varieties were preliminarily explored using fluorescence quantitative test. The relationship between VvAG and VvCRC, VvAG and VvAGL11 were analyzed using Y1H assay. Our results showed that there were obvious abdominal sutures on the surface of expect for ‘Musct Hambourg’ grape, and existing poly carpels. The ovary development of ‘ShanPuTao’ and ‘GongNiang2Hao’ grape was completed when the inflorescence length was less than 1 cm, while the ‘Concord’ and ‘Musct Hambourg’ grape were fully developed when the length of inflorescence was 3–4 and 4–5 cm, respectively. VvAG and VvCRC began to express in large quantities after the formation of stamen primordia, while VvAGL11 during the forming of ovule primordia. Therefore, VvAG and VvCRC mainly regulated the development of stamens and carpels and also promote the development of ovules, while VvAGL11 major regulated the development of ovules. The promoters of VvCRC and VvAGL11 were bound by VvAG. This study provides an important theoretical basis for further research on the molecular mechanism of grape ovary development.

Overexpression of a pear B-class MADS-box gene in tomato causes male sterility

B-class MADS-box genes are sufficient for the specification of petals and stamens; however, the role of <italic>Tomato MADS-box protein 6</italic> (<italic>TM6</italic>) in seed formation in pear remains largely unknown. In this study, <italic>PbTM6a</italic> and <italic>PbTM6b</italic>, characterized as negative regulators of the response to GA₄₊₇, were identified as classic B-class MADS-box genes. Additionally, both of the genes encoding proteins carried the highly conserved MADS-box domain, and showed high expression levels in anther, petal and filament of 'Dangshansu'. Overexpression of <italic>PbTM6a</italic> in tomato reduced the number of seeds per fruit. Analysis of the anatomical structure of floral organs revealed that the reduction in seed number in transgenic fruits might be attributed to an obstacle of pollen release due to strongly formed stomium and limited ovary space of ovule development. Moreover, triphenyl tetrazolium chloride (TTC) staining and <italic>in vitro</italic> germination tests of pollen grains indicated that <italic>PbTM6a</italic> overexpression reduced pollen viability and germination rates. Reciprocal crosses showed that the reduction in seed number in transgenic fruits was dominantly caused by the decreased fertility of pollen grains. Subsequent scanning electron microscopy showed that sterile pollen grains were caused by abnormal pollen grains. Additionally, the reduced levels of jasmonic acid (JA), abscisic acid (ABA), indole-3-acetic acid (IAA) and gibberellin A3 (GA3) in transgenic stamens contributed to the development of sterile pollen. Collectively, our results reveal the role of <italic>PbTM6a</italic> genes in controlling male infertility and broaden our understanding of the mechanism underlying the function of B-class MADS-box genes in pear.

The role of phytohormones and their related miRNAs in sex differentiation of Xanthoceras sorbifolium Bunge

• Determined the influence of IAA, GA, ABA, ZT on sex differentiation of Xanthoceras sorbifolium . • Identified 20 significantly differently expressed miRNAs (83 miRNA/target pairs) being related to phytohormone synthesis and signal transduction during sex differentiation. Xanthoceras sorbifolium Bunge is an important woody oilseed tree in north China. However, its yield is severely restricted by a low ratio of female to male flowers, and little is known about the physiological and molecular mechanisms underlying the sex differentiation of flowers. Therefore, carrying out the research in its sex differentiation regulation mechanism is the basis of increasing seed yield. Here, we investigated the cytology of sex differentiation, the content and their ratios of indole-3-acetic acid (IAA), gibberellins (GA 3 ), zeatin (ZT), abscisic acid (ABA), the effects of plant growth regulators on flower development, and the expression profiles of phytohormone-related miRNAs. The results showed that both functional female and male flowers were bisexual at the early stage of flower bud differentiation, while the development of the pistils of male flowers and the stamens of female flowers was arrested at later stage of sex differentiation. Furthermore, IAA, ABA and ZT were shown to be beneficial to pistil development in X. sorbifolium . GA 3 was the key phytohormone in pistil abortion. High level of ABA/ZT was beneficial for microspore mother cell meiosis. ZT/IAA was probably related to pistil abortion. High level of ZT/GA 3 contributed to ovule development. Spraying 6-BA was more effective than GA 3 in increasing female-to-male ratio regardless of CK. In addition, several miRNAs played key roles in sex differentiation, especially miR393, miR396, and miR399. They participated in the regulation of pollen maturation and multiple phytohormone pathways. The present study comprehensively identified the roles of phytohormones and their related miRNAs during sex differentiation in X. sorbifolium , which will be a valuable resource for sex regulation using genetic and physiological methods in the future.

Pollination Bag Type Affects Ovule Development and Seed Yields inPinus taedaL.

AbstractLoblolly pine (Pinus taeda L.) is the most widely planted forest tree species in the United States. Most of the seedlings used to establish these plantations come from seed collected in open-pollinated seed orchards, but an increasing number are coming from controlled crosses, about 15%–20% of the loblolly pine seedling crops in the last five years. To produce this seed, millions of pollination bags are installed each spring in orchards throughout the southeastern United States; over 2.6 million bags were installed in 2022. This study evaluated 13 pollination bag types available for use in the mass production of control-cross seed. Using cone analysis, significant differences were found among bag types for the proportion of ovules resulting in filled seed, empty seed, and first-year aborts. Due to differences in the efficacy of orchard management, study trees varied greatly in their proportion of ovules resulting in filled seed and first-year aborts. Under good orchard management, open-pollinated cones had 72% of their ovules as filled seed and 12% in first-year aborted ovules. The best pollination bag type had 62% of its ovules as filled seed with 22% in first-year aborted ovules. These differences are apparently due to the quality of pollen used in the controlled crosses.Study Implications: Compared with open-pollinated families, full-sibling crosses among elite parents of loblolly pine produce more market value to landowners due to greater productivity, increased disease resistance, and enhanced stem form. Specific crosses of loblolly pine have occupied about 15%–20% of the recent seedling market because the seed are costly and difficult to produce. This study tested pollination bag types to determine their effectiveness in producing control-cross seed. Some bag types were superior in increasing seed yield, but seed yields for open-pollinated cones tended to be higher, suggesting problems in the control-cross process. Cone analysis is a useful tool for seed orchard managers to diagnose problems in seed production. Understanding and correcting these problems will help managers increase their production of full-sibling seed and lead to the establishment of new plantations with increased forest productivity.

BELL1 interacts with CRABS CLAW and INNER NO OUTER to regulate ovule and seed development in pomegranate.

Pomegranate (Punica granatum) flowers are classified as bisexual flowers and functional male flowers. Functional male flowers have sterile pistils that show abnormal ovule development. In previous studies, we identified INNER NO OUTER (INO), CRABS CLAW (CRC) and BELL1 (BEL1), which were specifically expressed in bisexual and functional male flowers. However, the functions of ovule identity genes and the mechanism underlying ovule sterility in pomegranate remain unknown. Here, we found that the integument primordia formed and then ceased developing in the ovules of functional male flowers with a vertical diameter of 8.1-13.0 mm. Megaspore mother cells were observed in bisexual flowers when the vertical diameters of flowers were 10.1-13.0 mm, but not in functional male flowers. We analyzed the expression patterns of ovule-related genes in pomegranate ovule sterility and found that PgCRC mRNA was highly expressed at a critical stage of ovule development in bisexual flowers. Ectopic expression of PgCRC and PgINO was sufficient to increase seed number in transgenic lines. PgCRC partially complemented the Arabidopsis (Arabidopsis thaliana) crc mutant, and PgINO successfully rescued the seeds set in the Arabidopsis ino mutant. The results of Y2H assays, BiFC assays and genetic data analyses showed that PgCRC and PgINO directly interact with PgBEL1. Our results also showed that PgCRC and PgINO could not interact directly with MADS-box proteins and that PgBEL1 interacted with SEPALLATA (PgSEP) proteins. We report the function of PgCRC and PgINO in ovule and seed development and show that PgCRC and PgINO interact with PgBEL1. Thus, our results provide understanding of the genetic regulatory networks underlying ovule development in pomegranate.

Transcriptome profile analysis reveals the regulation mechanism of pistil abortion in Handeliodendron bodinieri

Handeliodendron bodinieri is a rare and endangered plant that belongs to the family Sapindaceae. H.bodinieri is also a Chinese endemic dioecious tree/shrub with multifunctional applications in the fields of landscape, medicine and bioenergy (biodiesel production). H. bodinieri has unisexual flowers with an aborted pistil and stamen, which makes it an excellent model to explore sex differentiation and unisexual flower development in a woody tree. This study investigates the critical stage, process, and molecular mechanism of pistil abortion, leading to gender differentiation, using paraffin section and RNA-seq technology. The results, which led to a better understanding of the phenotypic characteristics during the pistil abortion process, demonstrated that pistil abortion occurred during the development of the ovule, i.e., from the two-nucleate embryo sac to the four-nucleate embryo sac in stage one (the diameters of the flower buds were 1.3–1.6 mm). At this stage, male flower pistils appeared to be thinner, shriveled, dark-colored, and less swollen than female flower pistils. Furthermore, using the RNA sequencing technique, a comparison of male and female flowers was made before and after abortion. It was revealed that 12 genes related to ovule development, such as INO, BEL1 and CRC, 24 genes related to plant hormones, such as AHP6, ARF, ERF and GID1, and 12 genes related to ROS, such as POD, SOD, CAT and RBOH, could be involved in the regulation of pistil abortion. Therefore, this study will provide a theoretical foundation for future conservation, breeding and application of H. bodinieri.

Effects of pre-bloom spraying thidiazuron and different embryo development media on seedless grape embryo rescue

ABSTRACT Embryo rescue technology has been widely applied in seedless grape breeding, but its success depends on many factors. Here, two Vitis vinifera seedless varieties ‘Qinhong No.2’ and ‘Qinhong No.10’ were used as research objects, the inflorescences were sprayed with 0.5 mg·L−1 thidiazuron 10 days before flowering, and then the ovules from open- and self-pollination of them were cultured in solid–liquid biphase MM3 media to investigate the effect of thidiazuron on embryo rescue. Under natural condition, the ovules of open- and self-pollination were inoculated onto three solid–liquid biphase media NN, ER, and MM3 to compare the efficiency of embryo rescue. The results showed that pre-bloom spraying thidiazuron significantly promoted ovule development and further improved the effect of embryo rescue in vitro. After applying thidiazuron, the embryo development rate, germination rate, and seedling rate of the four combinations reached 30.77%–42.62%, 29.36%–41.64%, and 22.02%–40.33%, respectively. Open-pollination of the two varieties provided better effects for culturing than their self-pollination, and the MM3 medium was always more suitable for embryo development than either the ER or NN medium. Furthermore, the germination rate of bare embryos of ‘Qinhong No. 10’ open-pollination on solid WPM medium surpassed that of ovules (without embryo stripping) on solid NN medium. HIGHLIGHTS Pre-bloom spraying TDZ could improve the effect of embryo rescue of seedless grape. The embryo rescue effect was better in open- than self-pollinated seedless grapes. Solid–liquid biphase MM3 was more suitable for embryo rescue than an ER or NN medium. The seedling rate of bare embryos on WPM medium exceeded that of ovules on NN medium. Overall, 2312 hybrids from the four combinations were obtained via embryo rescue.

Developing Genetic Engineering Techniques for Control of Seed Size and Yield.

Many signaling pathways regulate seed size through the development of endosperm and maternal tissues, which ultimately results in a range of variations in seed size or weight. Seed size can be determined through the development of zygotic tissues (endosperm and embryo) and maternal ovules. In addition, in some species such as rice, seed size is largely determined by husk growth. Transcription regulator factors are responsible for enhancing cell growth in the maternal ovule, resulting in seed growth. Phytohormones induce significant effects on entire features of growth and development of plants and also regulate seed size. Moreover, the vegetative parts are the major source of nutrients, including the majority of carbon and nitrogen-containing molecules for the reproductive part to control seed size. There is a need to increase the size of seeds without affecting the number of seeds in plants through conventional breeding programs to improve grain yield. In the past decades, many important genetic factors affecting seed size and yield have been identified and studied. These important factors constitute dynamic regulatory networks governing the seed size in response to environmental stimuli. In this review, we summarized recent advances regarding the molecular factors regulating seed size in Arabidopsis and other crops, followed by discussions on strategies to comprehend crops' genetic and molecular aspects in balancing seed size and yield.

The effect of different gelling agents as part of culture medium on the rate of cucumber (&lt;i&gt;Cucumis sativus&lt;/i&gt; L.) unpollinated ovules gynogenic development

Relevance. The induction of gynogenic development of the culture of unpollinated ovules of Cucumis sativus L., as a part of solid nutrient media agar-agar or Phytagel™ are used as a gelling agent. The gelling agent determines the mobilization of substances in the composition of the nutrient medium and has various effects on the explants, which affects the quality of the resulting regenerates. However, there are no scientific works that explaines the effect of these gelling agents on the development of ovules and compare them with each other for C. sativus L. The aim: investigate the effect of various gelling agent in the nutrient medium on the induction of gynogenesis and the development of cucumber unpollinated ovules.Materials and methods. There are two promising collection specimens of cucumber №58 and №831 of the laboratory of cucurbits crop breeding and seed production of FSBSI FSVC were included into research. IMC nutrient medium (Induction Medium for Cucurbitaceae) with 30 g/l sucrose, 200 mg/l ampicillin, 0.2 mg/l thidiazuron (TDZ) was used for the induction of gynogenesis; agar-agar at a concentration of 7 g/l or Phytagel™ at a concentration of 3.5 g/l was used as a gel-forming agents. Ovules were isolated from ovaries in the phase of half-opened flower (FL-1) and fully opened flower (FL). Cultivation was carried out in plastic Petri dishes with a diameter of 60 mm with an air gap of 28.8 cm3 – "KS No. 1", and glass culture jars with an air gap of 140 cm3 – "KS No. 2".Results. On containing Phytagel™ or agar-agar nutrient medium, the area of ovules during 30 days of cultivation increases irregularly. Coefficients of ovule enlargement between gelling agents differed from 1.7 to 2.6 times depending on the cultivation time. The average growth rate of ovules on media with Phytagel™ was 0.08 mm2/day, while on media with agar-agar it was 0.02 mm2/day. Gelling agents type and cucumber phenotype are significant factors affecting the increase in area of entered into unpollinated cucumber ovules culture. Herewith the share of the gelling agent effect was 55.01%, and the share of genotype effect was 14.53%. The effect of flower development stage or culture vessel type has not found for both of genotypes. In the study, it was possible to achieve the induction of gynogenesis in 67% of the unpollinated ovules genotype №831 on nutrient medium with agar-agar.Conclusion. Ovules development were faster on a nutrient medium using Phytagel™ as a gelling agent than on agaragar. At the same time, the percentage of induced ovules was significally higher on nutrient medium with agar-agar for both phenotypes. Gelling agents type and cucumber phenotype were found as significant factors of the induction and the development of unpollinated ovules.

Pivotal role of STIP in ovule pattern formation and female germline development in Arabidopsis thaliana.

In spermatophytes the sporophytic (diploid) and the gametophytic (haploid) generations co-exist in ovules, and the coordination of their developmental programs is of pivotal importance for plant reproduction. To achieve efficient fertilization, the haploid female gametophyte and the diploid ovule structures must coordinate their development to form a functional and correctly shaped ovule. WUSCHEL-RELATED HOMEOBOX (WOX) genes encode a family of transcription factors that share important roles in a wide range of processes throughout plant development. Here, we show that STIP is required for the correct patterning and curvature of the ovule in Arabidopsis thaliana. The knockout mutant stip-2 is characterized by a radialized ovule phenotype due to severe defects in outer integument development. In addition, alteration of STIP expression affects the correct differentiation and progression of the female germline. Finally, our results reveal that STIP is required to tightly regulate the key ovule factors INNER NO OUTER, PHABULOSA and WUSCHEL, and they define a novel genetic interplay in the regulatory networks determining ovule development.

Role of grapevine SEPALLATA-related MADS-box gene VvMADS39 in flower and ovule development.

Seedlessness is one of the most important breeding goals for table grapes; thus, understanding the molecular genetic regulation of seed development and abortion is critical for the development of seedless cultivars. In the present study, we characterized VvMADS39, a class E MADS-box gene of grapevine (Vitis vinifera) orthologous to Arabidopsis SEP2. Heterologous overexpression of VvMADS39 in tomato reduced the fruit and seed size and seed number. Targeted mutagenesis of the homologous SlMADS39 in tomato induced various floral and fruit defects. It could reasonable to suppose that active VvMADS39 expression in "Thompson Seedless" may restrict cellular expansion, resulting in the development of smaller fruits and seeds, VvMADS39 may play a role in the regulation of ovule development in grapevine and contributes to seedless fruit formation. In contrast, VvMADS39 suppression in "Red Globe" was associated with enhanced histone H3 lysine 27 trimethylation in the promoter region of VvMADS39, allowing normal ovule and fruit development; Meanwhile, VvMADS39 interacts with VvAGAMOUS, and the activity of the VvMADS39-VvAGAMOUS dimer to induce integument development requires the activation and maintenance of VvINO expression. The synergistic cooperation between VvMADS39 and related proteins plays an important role in maintaining floral meristem characteristics, and fruit and ovule development.