Anther Wall Research Articles

The ZmMYB84-ZmPKSB regulatory module controls male fertility through modulating anther cuticle-pollen exine trade-off in maize anthers.

Anther cuticle and pollen exine are two crucial lipid layers that ensure normal pollen development and pollen-stigma interaction for successful fertilization and seed production in plants. Their formation processes share certain common pathways of lipid biosynthesis and transport across four anther wall layers. However, molecular mechanism underlying a trade-off of lipid-metabolic products to promote the proper formation of the two lipid layers remains elusive. Here, we identified and characterized a maize male-sterility mutant pksb, which displayed denser anther cuticle but thinner pollen exine as well as delayed tapetal degeneration compared with its wild type. Based on map-based cloning and CRISPR/Cas9 mutagenesis, we found that the causal gene (ZmPKSB) of pksb mutant encoded an endoplasmic reticulum (ER)-localized polyketide synthase (PKS) with catalytic activities to malonyl-CoA and midchain-fatty acyl-CoA to generate triketide and tetraketide α-pyrone. A conserved catalytic triad (C171, H320 and N353) was essential for its enzymatic activity. ZmPKSB was specifically expressed in maize anthers from stages S8b to S9-10 with its peak at S9 and was directly activated by a transcription factor ZmMYB84. Moreover, loss function of ZmMYB84 resulted in denser anther cuticle but thinner pollen exine similar to the pksb mutant. The ZmMYB84-ZmPKSB regulatory module controlled a trade-off between anther cuticle and pollen exine formation by altering expression of a series of genes related to biosynthesis and transport of sporopollenin, cutin and wax. These findings provide new insights into the fine-tuning regulation of lipid-metabolic balance to precisely promote anther cuticle and pollen exine formation in plants.

ZmMs33 promotes anther elongation via modulating cell elongation regulators, metabolic homeostasis, and cell wall remodeling in maize

Plant cell elongation depends on well-defined gene regulations, adequate nutrients, and timely cell wall modifications. Anther size is positively correlated with the number and viability of pollen grains, while little is known about molecular mechanisms underlying anther cell elongation. Here, we found that properly activated cell elongation regulators at transcriptional levels in loss-of-function ZmMs33 mutant (ms33-6038) anthers failed to promote maize anther elongation. ZmMs33 deficiency disrupted metabolic homeostasis mainly by inhibiting both photosynthesis in anther endothecium and lipid accumulation in anther tapetum. Importantly, ms33-6038 anthers displayed ectopic, premature and excessive secondary cell wall thickening in anther middle layer, which constrained cell elongation structurally and blocked nutrient flows across different anther wall layers. The metabolic disorder was only found in ms33-6038 mutant rather than several representative male-sterility lines at transcriptional and post-translational levels. Collectively, the disordered metabolisms and blocked nutrient flows defeated the activated cell elongation regulators, and finally inhibited anther elongation and growth with a unique “idling effect” in ms33-6038 mutant.

Embryology of Ficus tuerckheimii (subg. Spherosuke, Moraceae) and its relevance in interactions with its pollinator wasps, Pegoscapus sp. (Agaonidae)

• Ficus tuerckheimii has two female floral morphs with dimorphic stigmas. • Both floral morphs form showed cohesive synstigmas. • Wet stigmas are described for the first time within the genus Ficus. • The development of the anther wall in male flowers is a basic type. • Several evidence suggest that F. tuerckheimii is actively pollinated. Species in the Ficus (Moraceae) genus carry an inflorescence called syconium, formed by a fleshy, urn-shaped receptacle. This study aims to i) describe the embryology of Ficus tuerckheimii flowers at different developmental stages and ii) determine whether this species is pollinated actively or passively. The species is monoecious, with protogynous syconia and diclinous flowers. The syconia contain two pistillate floral morphs: one sessile with a long style and a symmetrically bilobed stigma, the other pedicellate with a short style and asymmetrical stigmatic lobes. The ovule of each flower type can develop into a seed or a (parasitic or pollinator) wasp. The gynoecium is pseudomonomerous; the flowers form a cohesive synstigma due to the proximity of the stigmatic papillae, which facilitates pollen concentration and pollen tubes growth in neighboring flowers. The staminate flowers are pedicellate and unistaminate. The anther dehiscence is longitudinal, rotating horizontally to open and release bicellular pollen grains. The syconium includes three different trichome types whose functions remain unknown. The drupelet fruit has a pericarp conformed of a tanniferous exocarp, a parenchymatic mesocarp, and a schlerenchymatic endocarp. We detected the following embryological characteristics that were previously undescribed for the genus and are potentially informative for the systematics of the family: i) wet stigmas, ii) a basic anther wall with a non-persistent epidermis and a multiplicative middle layer, iii) pollen grains that can germinate within the anther, iv) a profuse nucellus that later forms a perisperm, and v) a persistent perisperm. Altogether, the synstigma, the low anther-to-ovule ratio (0.12 SD ± 0.031), the smooth pollen ornamentation, and the specialized pollen collection and transport structures (corbiculae) of its pollinator wasps ( Pegoscapus sp., Agaonidae) suggest that F. tuerckheimii is actively pollinated.

Sucrose rather than GA transported by AtSWEET13 and AtSWEET14 supports pollen fitness at late anther development stages.

Both sugar and the hormone gibberellin (GA) are essential for anther-enclosed pollen development and thus for plant productivity in flowering plants. Arabidopsis (Arabidopsis thaliana) AtSWEET13 and AtSWEET14, which are expressed in anthers and associated with seed yield, transport both sucrose and GA. However, it is still unclear which substrate transported by them directly affects anther development and seed yield. Histochemical staining, cross-sectioning and microscopy imaging techniques were used to investigate and interpret the phenotypes of the atsweet13;14 double mutant during anther development. Genetic complementation of atsweet13;14 using AtSWEET9, which transports sucrose but not GA, and the GA transporter AtNPF3.1, respectively, was conducted to test the substrate preference relevant to the biological process. The loss of both AtSWEET13 and AtSWEET14 resulted in reduced pollen viability and therefore decreased pollen germination. AtSWEET9 fully rescued the defects in pollen viability and germination of atsweet13;14, whereas AtNPF3.1 failed to do so, indicating that AtSWEET13/14-mediated sucrose rather than GA is essential for pollen fertility. AtSWEET13 and AtSWEET14 function mainly at the anther wall during late anther development stages, and they probably are responsible for sucrose efflux into locules to support pollen development to maturation, which is vital for subsequent pollen viability and germination.

The Loss-Function of the Male Sterile Gene ZmMs33/ZmGPAT6 Results in Severely Oxidative Stress and Metabolic Disorder in Maize Anthers

In plants, oxidative stress and metabolic reprogramming frequently induce male sterility, however our knowledge of the underlying molecular mechanism is far from complete. Here, a maize genic male-sterility (GMS) mutant (ms33-6038) with a loss-of-function of the ZmMs33 gene encoding glycerol-3-phosphate acyltransferase 6 (GPAT6) displayed severe deficiencies in the development of a four-layer anther wall and microspores and excessive reactive oxygen species (ROS) content in anthers. In ms33-6038 anthers, transcriptome analysis identified thousands of differentially expressed genes that were functionally enriched in stress response and primary metabolism pathways. Further investigation revealed that 64 genes involved in ROS production, scavenging, and signaling were specifically changed in expression levels in ms33-6038 anthers compared to the other five investigated GMS lines. The severe oxidative stress triggered premature tapetal autophagy and metabolic reprogramming mediated mainly by the activated SnRK1-bZIP pathway, as well as the TOR and PP2AC pathways, proven by transcriptome analysis. Furthermore, 20 reported maize GMS genes were altered in expression levels in ms33-6038 anthers. The excessive oxidative stress and the metabolic reprogramming resulted in severe phenotypic deficiencies in ms33-6038 anthers. These findings enrich our understanding of the molecular mechanisms by which ROS and metabolic homeostasis impair anther and pollen development in plants.

Functional analysis of flower development related gene SvGLOBOSA from Senecio vulgaris.

The unique capitulum of Asteraceae has important ornamental and research value. Few studies have described the complex molecular mechanism of flower development. In this study, SvGLOBOSA(SvGLO), the MADS-box gene of Senecio vulgaris, was identified by screening the transcriptome data, and its function was examined. The gene structure was analyzed and its function was predicted through bioinformatics. The relative expression levels in different tissues of wild-type S. vulgaris were analyzed by qRT-PCR. SvGLO was overexpressed in Solanum nigrum and morphological observations were made. Histological staining was used in analyzing the histological changes in the ovary of transgenic S. nigrum. The results showed that the open reading frame of SvGLO was 591 bp long, encoding 196 amino acids. It has typical MADS-box and K-box domains and contains a PI motif at the C-terminal. SvGLO belongs to the PI/GLO subfamily of class B MADS-box genes. qRT-PCR results showed that SvGLO was highly expressed in inflorescence tissues but not in vegetative organs. In SvGLO-overexpressed S. nigrum, the sepals showed some characteristics of petals, carpels transformed into stamen-like organs, and fruit development was abnormal. Histological staining revealed that the morphology of ovary wall cells of transgenic S. nigrum was similar to that of anther wall cells of the stamen of wild-type S. vulgaris. Therefore, SvGLO may be involved in the regulation of petal and stamen development in S. vulgaris.

The structures of floral organs and reproductive characteristics of an ornamental bamboo species, Pleioblastus pygmaeus

As a woody grass, bamboo has special reproductive habits with an extremely long vegetative phase. Pleioblastus pygmaeus is a kind of ornamental dwarf bamboo species with high ecological and economic value in China. There was no documentary record of the flowering of P. pygmaeus until 2015, which bloomed in the Bamboo Garden of Nanjing Forestry University. Generally, bamboo plants rarely bear fruit or have a low seed setting rate, but this species has a high seed production. This study explores developmental reasons using anatomical methods. The process of flower bud differentiation and a series of important reproductive development processes including anther wall development, microsporogenesis, megasporogenesis, male and female gametophyte development, and embryonic development were investigated sequentially. Each stamen contained three tetrasporangiate anthers and the development of anther wall was of Monocotyledonous type. The microspores finally matured into 3-celled pollen grains by two successive mitoses. The pistil was composed of three carpels, with an anatropous, tenuinucellate and bitegmic ovule in a single ovary. The formation of embryo sac belonged to Polygonum type. With three mitoses, functional megaspore developed into the embryo sac with eight nuclei within seven cells. The development of stamen and pistil was synchronous in the same floret. The development of embryo followed Grass type and the development of endosperm belonged to Nuclear type. The development of endosperm was earlier than that of embryo. The study enriches basic knowledge of reproductive biology of bamboo plants and is of great fundamental significance to furtherly explore flowering mechanism of P. pygmaeus and to cultivate bamboo plants sustainably.

Anther and ovule development in Pittosporopsis and its implications for the systematics of Metteniusaceae (Metteniusales)

Pittosporopsis Craib, previously considered a member of the Icacinaceae sensu lato (s.l.), was transferred recently to the expanded Metteniusaceae, a family of 11 genera that needs morphological reevaluation to assess possible synapomorphies given its new circumscription. We investigated the anther and ovule developmental characters of Pittosporopsis and compared them with those of other members of Metteniusaceae as well as Icacinaceae s.l. to the extent possible. These characters are important to establish morphological synapomorphies of Metteniusaceae and to provide insights into embryology of the early diverging clades of core asterids. Within the family, Pittosporopsis shares several uncommon embryological characters with both Metteniusa H. Karst. and Emmotum Ham., such as a connective with numerous tanniferous cells and two superposed ovules within one locule. The ovule of Pittosporopsis is bitegmic, the third report of this condition (after Emmotum and Quintinia Baker f.) in the recently recircumscribed campanulids. Characters not shared with other members of Metteniusaceae include an unusual outward protuberance in the anther wall derived from the division and enlargement of endothecial cells, and a hypostase connecting the embryo sac and the ovular vascular bundle. Interestingly, a hypostase is known from Bruniaceae, which is sister to the core campanulids. Although further studies are needed to fully characterize the embryology and floral development of Pittosporopsis and the other genera now placed in Metteniusaceae, our study provides new insights into the embryology of the first diverging campanulid clades.

Sinosenecio jiuzhaigouensis (Asteraceae, Senecioneae), a new species from Sichuan, China

Sinosenecio jiuzhaigouensis (Asteraceae, Senecioneae), a new species from Jiuzhaigou county in northwestern Sichuan province, China, is described and illustrated. This species is similar to S. hederifolius and S. cyclaminifolius in having ovate-cordate leaf blade and solitary capitula, but differs by having swollen (vs. not swollen) rhizomes and smaller capitula (2–3 vs. 4–5 cm in diameter). Two floral micromorphological characters (configuration of filament collars and of anther endothecial cell wall thickenings), achene surface feature, and chromosome number of the new species are reported.

New insights on the analysis of phytosterols in pollen and anther wall of tree peony (Paeonia ostii ‘Fengdan’) revealed by GC-MS/MS

Phytosterols exhibit a wide range of pharmacological activities and have no side-effects, which have attracted more and more attention. In this study, two pre-treatment methods (alkaline hydrolysis and acid-alkali hydrolysis) were performed in parallel for the first time to investigate the effects on phytosterol analysis. The aim is to develop an analytical method for phytosterols in pollen and anther wall of tree peony (Paeonia ostii ‘Fengdan’) by gas chromatography-mass spectrometry. The result indicated that the contents of phytosterols in pollen (3390.02 mg/100 g DW) and anther wall (929.70 mg/100 g DW) of P. ostii ‘Fengdan’ were relatively high. Meanwhile, eleven phytosterols were identified, among which five phytosterols were first identified in tree peony pollen. Moreover, the effects of wall breaking and different developmental stages on phytosterol contents of pollen and anther wall of P. ostii ‘Fengdan’ were also discussed. The result showed that wall breaking was beneficial to sterol detection of pollen, but not necessary for anther wall. For the best harvest time, the stage of S2 had the highest content of phytosterols. In conclusion, this study successfully establishes an analytical method for phytosterols by gas chromatography-mass spectrometry, and lays a foundation for the development and utilization of pollen and anther wall of P. ostii ‘Fengdan’ in functional foods and pharmaceutical industry.

Flower Bud Differentiation, Mega-micro Spore Production, and Male-female Gametophyte Development in Camellia weiningensis

Camellia weiningensis is a typical woody edible oil tree species in the northwest alpine area of Guizhou Province, China, but its embryological development is not fully elucidated. Here, we assessed flower bud differentiation, microsporogenesis, and male-female gametophyte development in this species. We performed cytological observations of flower bud development in C. weiningensis through conventional paraffin sectioning, scanning electron microscopy, and stereomicroscopy to establish the corresponding relationships between the external morphology and internal structure. The flowers were hermaphroditic and exhibited a short flower bud differentiation time. Although pistil development occurred later than stamen development, both organs matured synchronously before flowering. The anther contained four sacs that exhibited a butterfly shape in transverse sections. The anther wall comprised the epidermis, anther chamber inner wall, two middle layers, and a glandular tapetum (from outside to inside). Microspore mother cells formed a tetrahedral tetrad through meiosis, mature pollen was two-celled with three germination pores, and the ovary comprised three to five chambers (three chambers predominated). Multiple ovules were invertedly attached to the axial placentation and exhibited double integuments and a thin nucellus. The embryo sac exhibited Allium-type development, and the mature embryo sac was seven-celled and eight-nucleated. In C. weiningensis, embryonic development does not exhibit abnormalities, and stamen development occurs earlier than pistil development. During flower bud development, the inner development process of male and female cells can be judged according to their external morphological characteristics. Our results may provide a theoretical basis for regulating flowering in and the cross-breeding of C. weiningensis.

The R2R3-MYB gene CgMYB4 is involved in the regulation of cell differentiation and fiber development in the stamens of Chelone glabra L.

A Plantaginaceae flowering plant, Chelone glabra, is different from Arabidopsis thaliana and cotton (Gossypium hirsutum), as it produces fibers on the anther surface. However, the evolutionary molecular mechanism of how fiber development is controlled in the stamen is unclear. MYB genes are essential transcription factors for trichome and fiber development in plants. In this study, we isolated 29 MYB domain-containing sequences using early-stage anthers and several sets of degenerated primers conserved in the R2R3 domain of the MYB transcription factor. Among them, CgMYB4 is an R2R3-MYB gene encoding 281 amino acids. Phylogenetic analysis showed that CgMYB4 is closely related to GhMYB25L/AmMIXTA, which controls fiber initiation and development in cotton and epidermal cell differentiation in the petals of Antirrhinum. Semiquantitative RT-PCR analysis showed that CgMYB4 is strongly expressed at the stamens and carpels. Overexpression of CgMYB4 significantly enhanced root hair formation in transformed hairy roots, contrary to the root hair numbers, which were reduced in silenced CgMYB4 hairy roots. Moreover, overexpression of CgMYB4 also evidently promoted fiber development at filaments and conical cell-like epidermal cell increases at the anther wall. Our results showed that CgMYB4 is an R2R3-MYB gene and is positively involved in regulating cell division and fiber differentiation in the early stages of stamen development in C. glabra.

Biological features of Crocus speciosus M. Bieb. (Iridaceae family)

The paper presents the results of studying the decorative species Crocus speciosus. Some features of the formation and development of male and female generative spheres are presented. It is shown that the formed anther wall is generated by the epidermis, endothecium, middle layer and tapetum. The wall of the mature anther is formed by the epidermis, fibrous endothecium with fibrous thickening, and a tapetal spathella with sporopollenin orbicles. Analysis of mature pollen grains showed a rather high proportion of normal pollen grains (80%), which under favorable conditions indicates a high ability to effectively pollinate. The characteristics of the female generative sphere are also shown: three-celled ovary; anatropic, bitegmal, funicular, crassinucellate ovule; linear tetrad of megaspores; Polygonum-type of embryonic sac development. The processes of flowering, pollination and seed formation are described.

BHLH Transcription Factor NtMYC2a Regulates Carbohydrate Metabolism during the Pollen Development of Tobacco (Nicotiana tabacum L. cv. TN90).

Basic helix-loop-helix (bHLH) transcription factor MYC2 regulates plant growth and development in many aspects through the jasmonic acid (JA) signaling pathway, while the role of MYC2 in plant carbohydrate metabolism has not been reported. Here, we generated NtMYC2a-overexpressing (NtMYC2a-OE) and RNA-interference-mediated knockdown (NtMYC2a-RI) transgenic plants of tobacco (Nicotiana tabacum L. cv. TN90) to investigate the role of NtMYC2a in carbohydrate metabolism and pollen development. Results showed that NtMYC2a regulates the starch accumulation and the starch-sugar conversion of floral organs, especially in pollen. The RT-qPCR analysis showed that the expression of starch-metabolic-related genes, AGPs, SS2 and BAM1, were regulated by NtMYC2a in the pollen grain, anther wall and ovary of tobacco plants. The process of pollen maturation was accelerated in NtMYC2a-OE plants and was delayed in NtMYC2a-RI plants, but the manipulation of NtMYC2a expression did not abolish the pollen fertility of the transgenic plants. Intriguingly, overexpression of NtMYC2a also enhanced the soluble carbohydrate accumulation in tobacco ovaries. Overall, our results demonstrated that the bHLH transcription factor NtMYC2a plays an important role in regulating the carbohydrate metabolism during pollen maturation in tobacco.

Quantitative and qualitative study of endogenous and exogenous growth regulators in eggplant (Solanum melongena) microspore cultures

In eggplant microspore embryogenesis, embryos are produced and then transformed into undifferentiated calli, instead of developing as true embryos. This is the main current bottleneck that precludes this process from being efficient. In this work we aimed to shed light on the factors involved in the successful in vitro development of eggplant haploid embryos by evaluating the role of growth regulators (GRs) in this process. We analyzed the endogenous levels of different GRs, including auxins, cytokinins and gibberelins, as well as salicylic, jasmonic and abscisic acid, in microspores and microspore-derived embryos at different culture stages. We also analyzed the same GR profiles in leaf and anther wall tissues of different eggplant backgrounds. Finally, we assessed the application of different GR combinations to the culture medium. Our results showed that in eggplant there are no genotype-specific endogenous GR profiles that can be associated to a high embryogenic response. Instead, the embryogenic response seems related to different GR accumulation patterns during in vitro culture. The changes observed in the endogenous levels of salicylic and abscisic acid were not related to the embryo transition. There were, however, changes in the levels of indole acetic acid and dihydrozeatin. The best GR combination to promote callus production was 0.5 mg/L 1-naphthaleneacetic acid (NAA) and 0.5 mg/L 6-benzylaminopurine (BAP). A 20% reduction of NAA and BAP reduced embryo production but produced structures more anatomically similar to embryos. These results shed light on the role of GRs during the development of microspore-derived embryos in eggplant microspore cultures.

DCET1 Controls Male Sterility Through Callose Regulation, Exine Formation, and Tapetal Programmed Cell Death in Rice.

In angiosperms, anther development comprises of various complex and interrelated biological processes, critically needed for pollen viability. The transitory callose layer serves to separate the meiocytes. It helps in primexine formation, while the timely degradation of tapetal cells is essential for the timely callose wall dissolution and pollen wall formation by providing nutrients for pollen growth. In rice, many genes have been reported and functionally characterized that are involved in callose regulation and pollen wall patterning, including timely programmed cell death (PCD) of the tapetum, but the mechanism of pollen development largely remains ambiguous. We identified and functionally characterized a rice mutant dcet1, having a complete male-sterile phenotype caused by defects in anther callose wall, exine patterning, and tapetal PCD. DCET1 belongs to the RNA recognition motif (RRM)-containing family also called as the ribonucleoprotein (RNP) domain or RNA-binding domain (RBD) protein, having single-nucleotide polymorphism (SNP) substitution from G (threonine-192) to A (isoleucine-192) located at the fifth exon of LOC_Os08g02330, was responsible for the male sterile phenotype in mutant dcet1. Our cytological analysis suggested that DCET1 regulates callose biosynthesis and degradation, pollen exine formation by affecting exine wall patterning, including abnormal nexine, collapsed bacula, and irregular tectum, and timely PCD by delaying the tapetal cell degeneration. As a result, the microspore of dcet1 was swollen and abnormally bursted and even collapsed within the anther locule characterizing complete male sterility. GUS and qRT-PCR analysis indicated that DCET1 is specifically expressed in the anther till the developmental stage 9, consistent with the observed phenotype. The characterization of DCET1 in callose regulation, pollen wall patterning, and tapetal cell PCD strengthens our knowledge for knowing the regulatory pathways involved in rice male reproductive development and has future prospects in hybrid rice breeding.

Abnormal anther development leads to lower spikelet fertility in rice (Oryza sativa L.) under high temperature during the panicle initiation stage

BackgroundDecreased spikelet fertility is often responsible for reduction in grain yield in rice (Oryza sativa L.). In this study, two varieties with different levels of heat tolerance, Liangyoupeijiu (LYPJ, heat susceptible) and Shanyou63 (SY63, heat tolerant) were subjected to two temperature treatments for 28 days during the panicle initiation stage in temperature/relative humidity-controlled greenhouses: high temperature (HT; 37/27 °C; day/night) and control temperature (CK; 31/27 °C; day/night) to investigate changes in anther development under HT during panicle initiation and their relationship with spikelet fertility.ResultsHT significantly decreased the grain yield of LYPJ by decreasing the number of spikelets per panicle and seed setting percentage. In addition, HT produced minor adverse effects in SY63. The decreased spikelet fertility was primarily attributed to decreased pollen viability and anther dehiscence, as well as poor pollen shedding of the anthers of LYPJ under HT. HT resulted in abnormal anther development (fewer vacuolated microspores, un-degraded tapetum, unevenly distributed Ubisch bodies) and malformation of pollen (obscure outline of the pollen exine with a collapsed bacula, disordered tectum, and no nexine of the pollen walls, uneven sporopollenin deposition on the surface of pollen grains) in LYPJ, which may have lowered pollen viability. Additionally, HT produced a compact knitted anther cuticle structure of the epidermis, an un-degraded septum, a thickened anther wall, unevenly distributed Ubisch bodies, and inhibition of the confluent locule, and these malformed structures may be partially responsible for the decreased anther dehiscence rate and reduced pollen shedding of the anthers in LYPJ. In contrast, the anther wall and pollen development of SY63 were not substantially changed under HT.ConclusionsOur results suggest that disturbed anther walls and pollen development are responsible for the reduced spikelet fertility and grain yield of the tested heat susceptible variety, and noninvasive anthers and pollen formation in response to HT were associated with improved heat tolerance.

Role of MS1 homolog Ntms1 gene of tobacco infertility.

The sterile line is the basis of crop heterosis utilization. To broaden the sources of male sterility in tobacco, the Ntms1 (Nicotiana tabacum L. ms1) gene was cloned from the tobacco variety K326 by homologous cloning based on the Cams1 (Capsicum annuum L. ms1) gene sequence of male-sterility genes in pepper. The protein structure and physicochemical properties of the two genes were determined by bioinformatics analysis, and the function of the Ntms1 gene was verified by the CRISPR/Cas9 system. The results showed that the sequences of Ntms1 and Cams1 were 85.25% similar, and plant homeodomains were found in both genes; the physical and chemical properties were also very similar. It is speculated that the Ntms1 gene had the same function as the Cams1 gene in controlling male sterility. Compared to the wild-type plants, the filaments of the Ntms1 knockout mutant plants were shorter, and the stamen was shorter than the pistil. The anthers did not develop fully and had few viable pollen grains; the tapetum and the anther wall had developed abnormally, and the anther chamber was severely squeezed. The malondialdehyde content in the mutant plants was significantly higher than that in the wild-type plants, while self-fertility was significantly lower in the mutant plants. The results showed that the Ntms1 gene plays an important role in regulating fertility in tobacco.

Doubled Haploids in Eggplant.

Simple SummaryThis review compiles the most relevant advances made in the production of doubled haploid plants in eggplant, the application of doubled haploid lines in breeding programs, and the future perspectives for the development of alternative technologies for doubled haploid generation in this species.Eggplant is a solanaceous crop cultivated worldwide for its edible fruit. Eggplant breeding programs are mainly aimed to the generation of F1 hybrids by crossing two highly homozygous, pure lines, which are traditionally obtained upon several self crossing generations, which is an expensive and time consuming process. Alternatively, fully homozygous, doubled haploid (DH) individuals can be induced from haploid cells of the germ line in a single generation. Several attempts have been made to develop protocols to produce eggplant DHs principally using anther culture and isolated microspore culture. Eggplant could be considered a moderately recalcitrant species in terms of ability for DH production. Anther culture stands nowadays as the most valuable technology to obtain eggplant DHs. However, the theoretical possibility of having plants regenerated from somatic tissues of the anther walls cannot be ruled out. For this reason, the use of isolated microspores is recommended when possible. This approach still has room for improvement, but it is largely genotype-dependent. In this review, we compile the most relevant advances made in DH production in eggplant, their application to breeding programs, and the future perspectives for the development of other, less genotype-dependent, DH technologies.

Light and electron microscopies reveal unknown details of the pollen grain structure and physiology from Brazilian Cerrado species.

Pollen grains have a relatively simple structure and microscopic size, with two or three cells surrounded by the protective sporoderm at maturity. The viability and efficiency of pollen transport from anther to stigma depends on pollen physiological properties, especially the relative water content of the vegetative cell. Pollen transport is a crucial fate for most angiosperms that depends on biotic pollinators and studies focusing on understanding the morpho-physiological properties of pollen grains are still scarce, especially to tropical open physiognomies as the Brazilian Cerrado. Therefore, we investigate some structural and physiological aspects of pollen grains from six native species naturally growing in one Cerrado area: Campomanesia pubescens (Myrtaceae), Caryocar brasiliense (Caryocaraceae), Erythroxylum campestre (Erythroxylaceae), Lippia lupulina (Verbenaceae), Pyrostegia venusta (Bignoniaceae), and Xylopia aromatica (Annonaceae). We selected dehiscent anthers and mature pollen grains to analyze (1) the anther wall and pollen microstructure, (2) the pollen water status at the time of anther dehiscence, and (3) the pollen chemical compounds. In all analyzed species, the anther and pollen developed in a successfully way, and except for Caryocar brasiliense, all species were able to emit pollen tubes in the germination tests. As expected for a dry and open environment, most species dispersed their pollen grains in a partially dehydrated form, as indicated by our harmomegathy experiment. As indicated by our study, the pollen ability in preventing dissection, maintaining its viability in a dry and hot environment during its transport from anther to stigma, may be related to the sporoderm apertures and to the reserve compounds, mainly carbohydrates in the form of hydrolysable starch grains.