Sterile Plants Research Articles

Environment-sensitive genic male sterility in rice and other plants.

Environment-sensitive genic male sterility is a type of male sterility that is affected by both genetic and environmental factors. Environment-sensitive genic male sterile lines are not only used in two-line hybrid breeding but are also good materials for studying plant-environment interactions. In this study we review the research progress on environment-sensitive genic male sterility in rice from the perspectives of epigenetic, transcriptional, posttranscriptional, posttranslationaland metabolic mechanisms as well as signal transduction processes. While significant progress has been made in the genetics, gene cloningand understanding of the molecular mechanisms of environment-sensitive genic male sterility in recent years, the relevant regulatory network is still poorly understood in rice. We therefore also review studies of environment-sensitive genic male sterility in Arabidopsis and other crops, hoping to promote research in this field in rice. Finally, we analyse the challenges posed by environment-sensitive genic male sterility and provide corresponding suggestions. This review will contribute towards an understanding the molecular genetics of environment-sensitive genic male sterility and its application in two-line hybrid breeding in rice and other species.

The Effects of Rf4 and the Genetic Mechanism Behind Fertility Restoration of Wild Abortive Cytoplasmic Male Sterility (WA-CMS) in Japonica Rice (Oryza sativa ssp. Japonica)

Wild abortive-type cytoplasmic male sterility (WA-type CMS) has been exclusively used in hybrid seed production in indica rice cultivars, and fertility restoration in WA-type CMS is controlled by two major restorer genes, Rf3 and Rf4, through a sporophytic mechanism. However, the genetic mechanism underlying fertility restoration in WA-type CMS in japonica cultivars is poorly understood. In the present study, C418, a leading Chinsurah Boro II- (BT)-type japonica restorer line, showed partial restoration ability in WA-type japonica CMS lines. The 1:1 segregation ratio of partially fertile to sterile plants in a three-cross F1 population indicated that fertility restoration is controlled by one dominant gene. Gene mapping and sequencing results revealed that the target gene should be Rf4. The Rf4 gene restores fertility through a sporophytic mechanism, but the Rf4 pollen grains show a preferential fertilization in the testcross F1 plants. Furthermore, Rf4 was confirmed to have only a minor effect on fertility restoration in WA-type japonica CMS lines, and Rf gene dosage effects influenced the fertility restoration of WA-type CMS in japonica rice. The results of our study not only provide valuable insights into the complex genetic mechanisms underlying fertility restoration of WA-type CMS but will also facilitate the efficient utilization of WA-type CMS in japonica rice lines.

Microbiome contributes to phenotypic plasticity in saffron crocus.

Saffron crocus is a sterile plant species that propagates vegetatively, and consequently, narrow genetic variation is detected in this species. Besides the narrow genetic variation, there is significant phenotypic variation in different traits in this plant. Here we tested this hypothesis that plant microbiome is a major contributor to the phenotypic variation. We focused our analysis on culturable bacteria that were dominant in saffron fields with high stigma yield compared to the fields with low stigma yield. Following this strategy, four rhizospheric (Cupriavidus metallidurans, Bacillus sp., Solibacillus sp., and Planococcus sp.) and two endophytic bacteria (Serratia oryzae and S. odorifera) were identified. The effects of the bacteria on the growth and development of the model plant Arabidopsis were assessed both in agar plate and pot assays. Results showed that these bacteria influence the vegetative growth and flowering time of Arabidopsis. In the next step, corms of saffron were inoculated with these bacteria and the growth and development of the saffron plants were monitored for five months. Remarkably, inoculation of the bacteria had significant influence on vegetative growth, flowering time, and stigma yield of saffron crocus. Furthermore, one of the bacteria, C. metallidurans, is reported here for the first time as a naturally occurring plant-associated bacteria. Altogether our results suggest that plant microbiome is an important factor in phenotypic variation in saffron crocus.

Long-term Studies of Annual Variation in Growth and Reproduction of the Understory Fern Steiropteris deltoidea in a Hurricane-prone Rainforest in Puerto Rico

Two long-term studies were conducted in a rainforest in Puerto Rico that included measurements of leaf and plant functional traits of the common fern species Steiropteris deltoidea. A Fern Demography study (1993-2009) compared annual variation and effects of a category 3 hurricane (Georges, 1998) on fertile and sterile leaf traits. A second long-term study (2003-2019), the Canopy Trimming Experiment, evaluated annual variation in growth and reproduction of S. deltoidea in response to two experimentally simulated and one category 4 hurricane (Maria, 2017). In the Fern Demography study, differences between fertile and sterile leaf production rates and plant leaf count of S. deltoidea were significant while leaf lengths and lifespans did not differ between leaf types. Fertile (but not sterile) leaf production increased three-fold after Hurricane Georges but declined 10-fold by the end of the study. Leaf lifespans of cohorts emerging before and in the three years after Hurricane Georges were significantly shortened by tree and debris fall. Elevated production of fertile leaves and increased plant leaf counts followed the two simulated hurricanes of the Canopy Trimming experiment and two natural hurricanes. Steiropteris deltoidea exhibits a level of interannual flexibility in some growth and reproductive traits in response to a changed understory environment that suggests it may be a good indicator species for evaluating microhabitat hurricane effects. Although S. deltoidea exhibited resilience, predicted increases in frequency and magnitude of hurricanes in response to climate change may test the limits of life history strategies of rainforest understory ferns.

High-temperature stress in crops: male sterility, yield loss and potential remedy approaches.

Global food security is one of the utmost essential challenges in the 21st century in providing enough food for the growing population while coping with the already stressed environment. High temperature (HT) is one of the main factors affecting plant growth, development and reproduction and causes male sterility in plants. In male reproductive tissues, metabolic changes induced by HT involve carbohydrates, lipids, hormones, epigenetics and reactive oxygen species, leading to male sterility and ultimately reducing yield. Understanding the mechanism and genes involved in these pathways during the HT stress response will provide a new path to improve crops by using molecular breeding and biotechnological approaches. Moreover, this review provides insight into male sterility and integrates this with suggested strategies to enhance crop tolerance under HT stress conditions at the reproductive stage.

Detection of seed purity of hybrid wheat using reflectance and transmittance hyperspectral imaging technology

Chemical hybridization and genic male sterility systems are two main methods of hybrid wheat production; however, complete sterility of female wheat plants cannot be guaranteed owing to the influence of the growth stage and weather. Consequently, hybrid wheat seeds are inevitably mixed with few parent seeds, especially female seeds. Therefore, seed purity is a key factor in the popularization of hybrid wheat. However, traditional seed purity detection and variety identification methods are time-consuming, laborious, and destructive. Therefore, to establish a non-destructive classification method for hybrid and female parent seeds, three hybrid wheat varieties (Jingmai 9, Jingmai 11, and Jingmai 183) and their parent seeds were sampled. The transmittance and reflectance spectra of all seeds were collected via hyperspectral imaging technology, and a classification model was established using partial least squares-discriminant analysis (PLS-DA) combined with various preprocessing methods. The transmittance spectrum significantly improved the classification of hybrids and female parents compared to that obtained using reflectance spectrum. Specifically, using transmittance spectrum combined with a characteristic wavelength-screening algorithm, the Detrend-CARS-PLS-DA model was established, and the accuracy rates in the testing sets of Jingmai 9, Jingmai 11, and Jingmai 183 were 95.69%, 98.25%, and 97.25%, respectively. In conclusion, transmittance hyperspectral imaging combined with a machine learning algorithm can effectively distinguish female parent seeds from hybrid seeds. These results provide a reference for rapid seed purity detection in the hybrid production process. Owing to the non-destructive and rapid nature of hyperspectral imaging, the detection of hybrid wheat seed purity can be improved by online sorting in the future.

In Vitro Culture as a Tool for Studying Plant Developmental Processes at the Physiological Level in Poland

Abstract Over the last 40 years, in vitro tissue culture has developed dynamically and has become a popular technique for scientific research in the field of biology. Initially, studies were carried out to develop procedures to obtain callus cultures, cell suspensions, and protoplasts of various plant species. Over time, these cultures have been used to analyze the course of processes and mechanisms that occur at the cellular level, including the course of embryological development, formation of cellular structures, polyploidization, signal transduction, gene expression, and responses to various stress factors. In a minireview, different nutritional, hormonal, atmospheric, and light conditions occurring in in vitro cultures, which are stressful conditions compared to those in ex vitro plant culture, were discussed. In this review, some examples of physiological studies conducted on in vitro culture by Polish scientists are presented, including studies carried out to optimize the composition of media that induce callus and plant regeneration; determine the use of in vitro culture for the preservation of endangered plant species; understand the mechanisms of resistance responses to pathogens, salinity, nutritional stress, and low temperatures; and determine the potential production of plants with different chemical compositions. The potential of sterile plant culture is large and beyond the scope of its current use. Therefore, the number and variety of applications of these cultures will be significantly greater in the future.

INITIATION STAGE OF GRAPES IN VITRO CULTURE AS A CRITICAL STAGE OF PLANT CLONAL MICROPROPAGATION

Initiation stage of in vitro culture of grapes is a critical stage of clonal micropropagation, the purpose of which is to obtain the maximum number of sterile and viable regenerative plants.
 Modern varieties are hybrids between the main species of Vitis vinifera, V. labrusca, V. riparia, V. amurensis, V. rupestris,
 V. berlandieri and V. lincecumii, which require the selection of optimal cultivation conditions: the timing of initiation,
 concentration and sterilization exposure time, mineral and hormonal composition of nutrient media, the use of additional
 biologically active substances to improve regeneration processes.

Mutagenic effectiveness and efficiency of gamma rays and combinations with EMS in the induction of macro mutations in blackgram (Vigna mungo (L.) Hepper)

Blackgram, an important pulse crop of India and other Asian countries, is a rich source of protein. Genetic improvement in this crop is generally slow-paced due to the lack of wide genetic variability available for selection. To create variability for important morphological traits and yield, induced mutagenesis was attempted in a popular blackgram cultivar CO 6 using gamma rays (γ rays-60Co) and a combination of ethyl methanesulphonate (EMS) and gamma rays. In M1 generation, the mutagenic treatments of 200 Gy γ rays and 200 Gy + 20 mM EMS showed a high percentage of viable and chlorophyll mutants. However, in M2 generation, 400 Gy + 20 mM EMS generated a higher proportion of viable mutations. A broad spectrum of viable macro mutants namely variation in growth habit, duration, size of leaf and pod, nature of pod and seed, seed yield and protruded stigma mutant were observed. The combination treatments exhibited a maximum frequency of viable macro mutations. Among viable macro mutations, the growth habit mutants recorded maximum frequency, followed by leaf mutants and pod mutants. The protruded stigma mutant was isolated at the higher dose of 400 Gy of γ rays. Studies on palynological traits among fertile and sterile plants using Scanning Electron Microscopy (SEM) revealed variations in pollen and anther length and shape among the mutants. The pollen lumina and muri shape in the fertile plant were observed as polygonal and narrow straight, whereas it was collapsed in the sterile plant. The inheritance pattern for most of the viable macro mutants was true-breeding which was further confirmed in the M3 generation. These viable mutants could be used for the blackgram improvement program.

Реакция образцов озимого ячменя на обработку семян химическими мутагенами

In nature, a huge variety of traits is created in the systems of living organisms due to the occurrence of mutations. The use of ionizing radiation, ultraviolet rays, and many chemical compounds makes it possible to significantly increase the frequency of gene mutations, the genotypic and phenotypic variability of traits, and to achieve a sharp increase in the efficiency of artificial selection and the intensity of the selection process. The genotypic flexibility of the population and selection ensure adaptation to long-term changes in environmental factors. In the present work, the specificity of the mutagenic effect of some chemical mutagens on the winter barley variety Ardak on the variability of population and individual traits was studied for the first time. Our goal was to study the effect of carbolite and N-nitrosomethylurea in different concentrations on the agrobiological characteristics of winter barley. The scientific novelty of the conducted research lies in the study of the effect of carbolite and N-nmm in different concentrations on the agrobiological characteristics of winter barley, as well as on the content of total nitrogen and proteins in barley grains at previously unused or little studied doses. The object of the study was the seeds of barley variety Ardak. Carbolite compounds, N-nitrosomethyl urea were used as mutagenic factors. Carbolite was used at a concentration of 2n, the seeds were treated with carbolite solution for 6, 12, 18 and 24 hours. In the present studies, N-nitrosomethyl urea was used at concentrations of 0.012% and 0.025%. Barley seeds were treated with aqueous solutions of the mutagen for three hours, and then washed in running water at a temperature of 22 °C for 30 minutes. Control seeds were soaked in water. After treatment, the seeds were dried on filter paper and sown in the soil after 10 days. Each option contains 250 seeds. Seed germination was counted after two weeks. Subsequently, the linear parameters of plants were measured every 10 days. After harvesting, the plants were analyzed for morphological changes and the total percentage of changed plants was calculated. In addition, the sign was studied — the weight of 1000 grains. Seeds of the first generation for the next year were sown in the soil according to the treatment options (250 pieces). Second generation plants were analyzed in the same way as M1 plants. Next, a biochemical analysis of the seeds was carried out to determine the total amount of nitrogen and protein according to the treatment options. The Kjeldahl micro-method was used to determine total nitrogen. As a result of the research, it was found that carbolite at a concentration of 2n in 6- and 18-hour exposures stimulates the content of total nitrogen and protein in the first generation in grains of barley variety Ardak. It has an overwhelming effect on the biochemical processes of barley seeds in the second generation. At the same time, carbolite inhibits the development of barley and causes the appearance of a large number of speltoid and sterile plants. But at the same time, it should be emphasized that a large number of speltoids and sterile plants in the variants treated with carbolite decreases in the second generation. N-nmm at concentrations of 0.012% and 0.025% contribute to an increase in the content of total nitrogen and protein in barley grains. The increased content of nitrogen and protein in the treated N-nmm variant is preserved in the second generation. It should be noted that N-nmm at a concentration of 0.012% is more effective for this variety than at a concentration of 0.025%. Also, N-nmm inhibits the development of barley and causes a large number of morphological changes. In a comparative study of the effect of mutagens N-nmm and carbolite on the content of the total amount of nitrogen and protein, it was found that N-nmm contributes to an increase in the amount of nitrogen and protein, while carbolite decreases.

Fine Mapping and Gene Analysis of restorer-of-fertility Gene CaRfHZ in Pepper (Capsicum annuum L.).

Cytoplasmic male sterility (CMS) is a common biological phenomenon used in hybrid production of peppers (Capsicum annuum L.). Although several restorer-of-fertility (Rf) genes of pepper CMS lines have been mapped, there is no report that the Rf gene with clear gene function has been isolated. Here, pepper CMS line HZ1A and its restorer line HZ1C were used to construct (HZ1A × HZ1C) F2 populations and map the Rf gene. A single dominant gene CaRfHZ conferred male fertility according to inheritance analysis. Using sterile plants from (HZ1A × HZ1C) F2 populations and bulked segregant analysis (BSA), the CaRfHZ gene was mapped between P06gInDel-66 and P06gInDel-89 on chromosome 6. This region spans 533.81 kb, where four genes are annotated according to Zunla-1 V2.0 gene models. Based on the analysis of genomic DNA sequences, gene expressions, and protein structures, Capana06g002968 was proposed as the strongest candidate for the CaRfHZ gene. Our results may help with hybrid pepper breeding and to elucidate the mechanism of male fertility restoration in peppers.

Identification of a Male Sterile Candidate Gene in Lilium x formolongi and Transfer of the Gene to Easter Lily (L. longiflorum) via Hybridization.

Pollen-free varieties are advantageous in promoting cut-flower production. In this study, we identified a candidate mutation which is responsible for pollen sterility in a strain of Lilium × formolongi, which was originally identified as a naturally occurred male-sterile plant in a seedling population. The pollen sterility occurred due to the degradation of pollen mother cells (PMCs) before meiotic cell division. Genetic analysis suggested that the male-sterile phenotype is attributed to one recessive locus. Transcriptome comparison between anthers of sterile and fertile plants in a segregated population identified a transcript that was expressed only in pollen-fertile plants, which is homologous to TDF1 (DEFECTIVE in TAPETAL DEVELOPMENT and FUNCTION1) in Arabidopsis, a gene encoding a transcription factor AtMYB35 that is known as a key regulator of pollen development. Since tdf1 mutant shows male sterility, we assumed that the absence transcript of the TDF1-like gene, named as LflTDF1, is the reason for pollen sterility observed in the mutant. A 30 kbp-long nanopore sequence read containing LflTDF1 was obtained from a pollen-fertile accession. PCR analyses using primers designed from the sequence suggested that at least a 30kbp-long region containing LflTDF1 was deleted or replaced by unknown sequence in the pollen-sterile mutant. Since the cross between L. × formolongi and Easter lily (L. longiflorum) is compatible, we successfully introgressed the male-sterile allele, designated as lfltdf1, to Easter lily. To our knowledge, this is the first report of molecular identification of a pollen-sterile candidate gene in lily. The identification and marker development of LflTDF1 gene will assist pollen-free lily breeding of Easter lilies and other lilies.

Fine mapping of Rf2, a minor Restorer-of-fertility (Rf) gene for cytoplasmic male sterility in chili pepper G164 (Capsicum annuum L.).

Genome re-sequencing and recombination analyses identified Capana06g000193 as a strong candidate for the minor male fertility restoration locus Rf2 in chili pepper G164 harboring two dominant male fertility restoration genes. Male fertility restoration genes of chili pepper restorer line G164 (Capsicum annuum L.) were studied using molecular marker genotypes of an F2 population (7G) of G164 crossed with the cytoplasmic male sterility line 77013A. The ratio of sterile to fertile single plants in the F2 population was 1:15. This result indicates that chili pepper G164 has two dominant restoration genes, which we designated as Rf1 and Rf2. An individual plant recessive for Rf1 and heterozygous for Rf2, 7G-112 (rf1rf1Rf2rf2), was identified by molecular marker selection and genetic analysis, and a single Rf2 gene-segregating population with a 3:1 ratio of fertile to sterile plants was developed from the self-pollination of male fertile individuals of 77013A and 7G-112 hybrid progeny. Bulk segregant analysis of fertile and sterile pools from the segregating populations was used to genetically map Rf2 to a 3.1-Mb region on chromosome 6. Rf2 was further narrowed to a 179.3-kb interval through recombination analysis of molecular markers and obtained the most likely candidate gene, Capana06g000193.

Pollination by the hoverflyEristalinus aeneus(Diptera: Syrphidae) in two hybrid seed crops: celery and fennel (Apiaceae)

AbstractHybrid seed production often relies on managed pollinators whose use in isolation cages can pose challenges. Here, we evaluated the pollination ability of the novel managed pollinatorEristalinus aeneus(Diptera: Syrphidae) in hybrid celery and fennel seed crops. During trials performed in 2019–2020 in Cordoba, Spain, we compared seed production with hoverflies released at high and low densities (40–20 ind./m2), and without released pollinators. In celery, we included a treatment withLucilia sericata(Diptera: Calliphoridae), a blowfly used for seed production (375 ind./m2). The production of celery seeds whenE. aeneuswere released at high density was significantly higher (+49%) than without released pollinators, for both sterile and fertile plant genotypes; no significant differences were found between the two hoverfly densities and the blowfly treatments. In fennel, seed yield of fertile plants with high density of hoverflies was higher than with low density (+149%), or without released pollinators (+168%); whereas for sterile plants no differences were found between treatments. In both crops and plant genotypes, the highest pollen adhesion to stigmas (number of pollen grains and proportion of flowers with pollen adhered in two stigmas) was obtained with hoverflies at high density. In celery, pollen adhesion was higher with high density of hoverflies than with blowflies for both plant genotypes, despite the considerably lower numbers of released hoverflies. Our results suggest thatE. aeneusis a more efficient pollinator of celery thanL. sericata, and that it has the potential to effectively pollinate other hybrid Apiaceae seed crops like fennel.

Once more unto the breach, dear friends: Resolving the origins and relationships of the Pellaea wrightiana hybrid complex.

The taxonomic status of Wright's cliff brake fern, Pellaea wrightiana, has been in dispute ever since it was first described by Hooker in 1858. Previously published evidence suggested that this "taxon" may represent a polyploid complex rather than a single discrete species, a hypothesis tested here using a multifaceted analytical approach. Data derived from cytogenetics, spore analyses, leaf morphometrics, enzyme electrophoresis, and phylogenetic analyses of plastid and nuclear DNA sequences are used to elucidate the origin, relationships, and taxonomic circumscription of P. wrightiana. Plants traditionally assigned to this taxon represent three distinct polyploids. The most widespread, P. wrightiana, is a fertile allotetraploid that arose through hybridization between two divergent diploid species, P. truncata and P. ternifolia. Sterile triploids commonly identified as P. wrightiana, were found to be backcross hybrids between this fertile tetraploid and diploid P. truncata. Relatively common across Arizona and New Mexico, they are here assigned to P. ×wagneri hyb. nov. In addition, occasional sterile tetraploid plants assigned to P. wrightiana are shown here to be hybrids between the fertile allotetraploid and the tetraploid P. ternifolia subsp. arizonica. These tetraploid hybrids originated independently in two regions of parental sympatry (southern Arizona and west Texas) and are here assigned to P. ×gooddingii hyb. nov. Weaving together data from a diversity of taxonomic approaches, we show that plants identified as P. wrightiana represent three morphologically distinguishable polyploids that have arisen through repeated hybridization events involving the divergent sexual taxa P. ternifolia and P. truncata.

Light and auxin treatments affect morphogenesis and polyphenolics productivity in Artemisia alba Turra cell aggregates in vitro

Artemisia alba Turra is an essential oil-bearing shrub, with a Euro-Mediterranean distribution widespread in the south-eastern parts of Europe. Phytochemical investigations have evidenced the presence of volatile mono- and sesquiterpene derivatives, as well as non-volatile sesquiterpenoids, flavonoids and phenolic acids contributing to the anti-inflammatory, antimicrobial, antioxidant and pro-apoptotic activity of different preparations, obtained from the plant. The current research aims at elucidation of the potential for biotechnological polyphenolic compounds productivity of non-differentiated cell lines of the plant. For this purpose, non-differentiated cell aggregates were initiated from either leaf or root explants of the sterile grown plant. They were cultivated either in the dark or at 16/8 h photoperiod in liquid media, supplemented with N6-benzyladenine (BA) as auxin. The cytokinin effects of indole-3-butyric acid (IBA) and 1-naphthalene acetic acid (NAA) were compared. It was established that NAA supplementation was superior to IBA and light treatment – to dark growth conditions in terms of polyphenolics productivity. In addition, NAA supplementation led to better expressed compaction and larger size of the cell aggregates as compared with IBA. The results of the present experiment indicate that secondary metabolites productivity in vitro is a dynamic process closely related to the plant’s growth and development and is in close relation to the interactions of the plant with its environmental conditions.

The changes of economically valuable signs got under the influence of gamma-ryes

Relevance. The plants treated and modified under the influence of a physical mutagen of the Co60 isotope at doses of 500, 1000, 5000, 10000, 20000 and 30000 r were grouped into types. Changes in such economically valuable features as yield per one bush, fiber yield, weight of raw cotton in one boll and fiber length under the influence of the Co60 isotope in experimental optionss were studied. With an increase in the dose of gamma rays, an increase in fiber yield was observed. In the AzNIHI-195 variety, when exposed to a lower dose of gamma rays (500 R) on seeds before sowing, the fiber yield was 35.9%, at a high dose (30,000 R) — 37.2%. Fiber yield varies depending not only on the variety, but also on the placement of the bolls on the bush. Forms with short and long fibers selected according to various options are of particular importance as a starting material and on their basis, in the next generation, it is possible to select forms with long fibers. The resulting economically valuable forms will be used as starting material in breeding work.Methods. The research studied the change in the mass of raw cotton of one boll under the influence of gamma rays on seeds. The results of the impact of gamma rays on the seeds of varieties AzNIKHI-104 and AzNIKHI-195 in M 1 shows a change in the mass of raw cotton in one boll. On this basis, sharp differences were obtained both in the effect of different doses of gamma rays among themselves, and in comparison with the control option. In the variety AzNIKHI-104 in M1, the obtained differences were at the ranges of 0.2–0.9 gr. At a high concentration of mutagens, a sharp change in the average weight of one boll was observed.Results. In both varieties, an increase in the dose of the mutagen leads to an increase in both the mass and the yield of raw cotton fiber, while the yield of raw cotton in one bush decreases. When exposed to high doses, low-yielding, semi-sterile and sterile plants are obtained, and the length of the fiber increases at low doses. A similar result is observed in both cotton varieties.

Overexpression of sesame polyketide synthase A leads to abnormal pollen development in Arabidopsis

BackgroundSesame is a great reservoir of bioactive constituents and unique antioxidant components. It is widely used for its nutritional and medicinal value. The expanding demand for sesame seeds is putting pressure on sesame breeders to develop high-yielding varieties. A hybrid breeding strategy based on male sterility is one of the most effective ways to increase the crop yield. To date, little is known about the genes and mechanism underlying sesame male fertility. Therefore, studies are being conducted to identify and functionally characterize key candidate genes involved in sesame pollen development. Polyketide synthases (PKSs) are critical enzymes involved in the biosynthesis of sporopollenin, the primary component of pollen exine. Their in planta functions are being investigated for applications in crop breeding.ResultsIn this study, we cloned the sesame POLYKETIDE SYNTHASE A (SiPKSA) and examined its function in male sterility. SiPKSA was specifically expressed in sesame flower buds, and its expression was significantly higher in sterile sesame anthers than in fertile anthers during the tetrad and microspore development stages. Furthermore, overexpression of SiPKSA in Arabidopsis caused male sterility in transgenic plants. Ultrastructural observation showed that the pollen grains of SiPKSA-overexpressing plants contained few cytoplasmic inclusions and exhibited an abnormal pollen wall structure, with a thicker exine layer compared to the wild type. In agreement with this, the expression of a set of sporopollenin biosynthesis-related genes and the contents of their fatty acids and phenolics were significantly altered in anthers of SiPKSA-overexpressing plants compared with wild type during anther development.ConclusionThese findings highlighted that overexpression of SiPKSA in Arabidopsis might cause male sterility through defective pollen wall formation. Moreover, they suggested that SiPKSA modulates vibrant pollen development via sporopollenin biosynthesis, and a defect in its regulation may induce male sterility. Therefore, genetic manipulation of SiPKSA might promote hybrid breeding in sesame and other crop species.

General regulatory factor 3 regulates the expression of alternative oxidase 1a and the biosynthesis of glucosinolates in cytoplasmic male sterile Brassica juncea

Mitochondrial retrograde signaling (MRS) plays an essential role in sensing and responding to internal and external stimuli to optimize growth to adapt to the prevailing environmental conditions. Previously studies showed alterations on MRS in cytoplasmic male sterile (CMS) plant. However, the regulators involved in MRS in CMS plants remain largely unknown. In this study, we used alternative oxidase 1a (AOX1a) as an indicator of MRS and found that the expression of AOX1a was significantly downregulated in a CMS line comparing to its revertant line, thus indicating an alteration in MRS in the CMS line. By performing a BLAST search of known regulatory components involved in MRS in yeast, we identified general regulatory factor 3 (GRF3), an orthologue of Bmh1/2 in yeast, and demonstrated an association between this gene and MRS in plants, as evidenced by change in AOX1a expression. GRF3 protein was found to be located in the nucleus and the plasma membrane. Further studies showed that GRF3 interacted with MYB29, and regulated the biosynthesis of glucosinolates in Brassica juncea. These findings revealed that GRF3, a negative regulator of AOX1a, is involved in MRS, and also plays a vital role in the accumulation of glucosinolates in CMS crops.

The chimeric gene atp6c confers cytoplasmic male sterility in maize by impairing the assembly of the mitochondrial ATP synthase complex

Cytoplasmic male sterility (CMS) is a powerful tool for the exploitation of hybrid heterosis and the study of signaling and interactions between the nucleus and the cytoplasm. C-type CMS (CMS-C) in maize has long been used in hybrid seed production, but the underlying sterility factor and its mechanism of action remain unclear. In this study, we demonstrate that the mitochondrial gene atp6c confers male sterility in CMS-C maize. The ATP6C protein shows stronger interactions with ATP8 and ATP9 than ATP6 during the assembly of F1Fo-ATP synthase (F-type ATP synthase, ATPase), thereby reducing the quantity and activity of assembled F1Fo-ATP synthase. By contrast, the quantity and activity of the F1' component are increased in CMS-C lines. Reduced F1Fo-ATP synthase activity causes accumulation of excess protons in the inner membrane space of the mitochondria, triggering a burst of reactive oxygen species (ROS), premature programmed cell death of the tapetal cells, and pollen abortion. Collectively, our study identifies a chimeric mitochondrial gene (ATP6C) that causes CMS in maize and documents the contribution of ATP6C to F1Fo-ATP synthase assembly, thereby providing novel insights into the molecular mechanisms of male sterility in plants.