Tapetum-specific expression of a cytoplasmic orf507 gene causes semi-male sterility in transgenic peppers

The molecular mechanism and utilization of ZmMs7-mediated dominant nuclear sterility in Oryza sativa L

Introduction

Research on the molecular basis of dominant male sterility in rice and its application in sterile lines is significantly underdeveloped. This article aims to utilize dominant nuclear male sterile lines, which were created through the ectopic expression of ZmMs7 in the genetic background of rice, for the purpose of heterosis utilization.

Methods

At the same time, we conducted a study on the spatiotemporal expression characteristics of ZmMs7, performed transcriptome analysis, and implemented yeast two-hybrid experiments to elucidate its molecular regulatory mechanisms in mediating dominant nuclear male sterility in rice.

Results

The results confirm the successful construction of a dominant nuclear male-sterile (NMS) vector system (p5126-ZmMs7-DsRed) using the exogenous male-sterile gene ZmMs7. This system comprises three modules: first, a dominant nuclear male-sterile (NMS) functional module driven by p5126, designed to achieve the dominant nuclear male-sterile trait; second, a fluorescence-based selection module driven by the endosperm-specific promoter LTP2, which facilitates the expression of the red fluorescent protein gene DsRed; and finally, a herbicide resistance screening module driven by the constitutive CaMV35S promoter, enabling the expression of the selectable marker Bar gene. The system has successfully developed a practical dominant male-sterile rice line characterized by complete pollen sterility, stable fertility, and straightforward visual seed selection, with no adverse effects on plant growth. In the hybrid offspring, approximately 50% of the seeds are genetically modified fluorescent seeds, while the remaining seeds are non-genetically modified and non-fluorescent. Transgenic plants Pro5126: GUS and ProZmMs7: GUS do not exhibit expression in roots, stems, leaves, or glumes. It is proposed that p5126 may enhance the expression of the ZmMs7 gene, which could lead to the up-regulation of the rice pollen fertility gene RIP1, as well as the down-regulation of OsMADS5 and the leafy glume sterile genes OsMADS1 and LHS1.

Discussion

Furthermore, it was demonstrated that the proteins encoded by these three fertility genes interact with the protein encoded by ZmMs7. This study provides new insights into the molecular regulatory network governing male reproductive development in rice and offers a theoretical foundation and technical support for the development of novel male-sterile germplasm resources.

Comparative Analysis of the Mitochondrial Genome of Eggplant (Solanum melongena L.) to Identify Cytoplasmic Male Sterility Candidate Genes

Cytoplasmic male sterility (CMS) is important for commercial hybrid seed production. However, it is still not used in eggplant (Solanum melongena L.), and corresponding regulatory genes and mechanisms of action have not been reported. We report CMS line 327A, which was derived from the hybridization between cultivated and wild eggplants. By looking at different stages of anther development under a microscope, we saw that the 327A anther's tapetum layer vacuolized during meiosis, which caused abortion. To investigate the 327A CMS regulatory genes, the mitochondrial genomes of 327A and its maintainer line 327B were assembled de novo. It was found that 15 unique ORFs (Open Reading Frame) were identified in 327A. RT-PCR and RT-QPCAR tests confirmed that orf312a and orf172a, 327A-specific ORFs with a transmembrane domain, were strongly expressed in sterile anthers of 327A. In addition, orf312a has a chimeric structure with the ribosomal protein subunit rpl16. Therefore, orf312a and orf172a can be considered strong candidate genes for CMS. Concurrently, we analyzed the characteristics of CMS to develop a functional molecular marker, CMS312, targeting a future theoretical basis for eggplant CMS three-line molecular breeding.

The transcription factor TaGAMYB modulates tapetum and pollen development of TGMS wheat YanZhan 4110S via the gibberellin signaling

Male reproductive development in higher plants experienced a series of complex biological processes, which can be regulated by Gibberellins (GA). The transcriptional factor GAMYB is a crucial component of GA signaling in anther development. However, the mechanism of GAMYB in wheat male reproduction is less understood. Here, we found that the thermo-sensitive genic male sterilitywheat line YanZhan 4110S displayed delayed tapetum programmed cell death and pollen abortive under the hot temperature stress. Combined with RNA-Sequencing data analysis, TaGAMYB associated with fertility conversion was isolated, which was located in the nucleus and highly expressed in fertility anthers. The silencing of TaGAMYB in wheat displayed fertility decline, defects in tapetum, pollen and exine formation, where the abortion characteristics were the same as YanZhan 4110S. In addition, either hot temperature or GA3 treatment in YanZhan 4110S caused the downregulation of TaGAMYB at binucleate stage and trinucleate stage, as well as fertility decrease. Further, the transcription factor TaWRKY2 significantly changed under GA3-treatment and directly interacted with the TaGAMYB promoter by W-box cis-element. Therefore, we suggested that TaGAMYB may be essential for anther development and male fertility, and GA3 activates TaGAMYB by TaWRKY2 to regulate fertility in wheat.

Comparative Cytological and Transcriptome Analyses of Anther Development in Nsa Cytoplasmic Male Sterile (1258A) and Maintainer Lines in Brassica napus Produced by Distant Hybridization

1258A is a new line of B.napus with Nsa cytoplasmic male sterility (CMS) with potential applications in hybrid rapeseed breeding. Sterile cytoplasm was obtained from XinJiang Sinapis arvensis through distant hybridization and then backcrossed with 1258B for many generations. However, the characteristics and molecular mechanisms underlying pollen abortion in this sterile line are poorly understood. In this study, a cytological analysis revealed normal microsporogenesis and uninucleate pollen grain formation. Pollen abortion was due to non-programmed cell death in the tapetum and the inability of microspores to develop into mature pollen grains. Sucrose, soluble sugar, and adenosine triphosphate (ATP) contents during microspore development were lower than those of the maintainer line, along with an insufficient energy supply, reduced antioxidant enzyme activity, and substantial malondialdehyde (MDA) accumulation in the anthers. Transcriptome analysis revealed that genes involved in secondary metabolite biosynthesis, glutathione metabolism, phenylpropane biosynthesis, cyanoamino acid metabolism, starch and sucrose metabolism, and glycerolipid metabolism may contribute to pollen abortion. The down regulation of nine cytochrome P450 monooxygenases genes were closely associated with pollen abortion. These results suggest that pollen abortion in 1258A CMS stems from abnormalities in the chorioallantoic membranes, energy deficiencies, and dysfunctional antioxidant systems in the anthers. Our results provide insight into the molecular mechanism underlying pollen abortion in Nsa CMS and provide a theoretical basis for better heterosis utilization in B.napus.

Orf165 is associated with cytoplasmic male sterility in pepper

Cytoplasmic male sterility (CMS) is a maternally inherited trait that derives from the inability to produce functional pollen in higher plants. CMS results from recombination of the mitochondrial genome. However, understanding of the molecular mechanism of CMS in pepper is limited. In this study, comparative transcriptomic analyses were performed using a near-isogenic CMS line 14A (CMS-14A) and a maintainer line 14B (ML-14B) as experimental materials. A total of 17,349 differentially expressed genes were detected between CMS-14A and ML-14B at the PMC meiosis stage. Among them, six unigenes associated with CMS and 108 unigenes involved in energy metabolism were identified. The gene orf165 was found in CMS-14A. When orf165 was introduced into ML-14B, almost 30% of transgenic plants were CMS. In addition, orf165 expression in transgenic CMS plants resulted in abnormal function of some genes involved in energy metabolism. When orf165 in transgenic CMS plant was silenced, the resulted orf165-silenced plant was male fertile and the expression patterns of some genes associated with energy metabolism were similar to ML-14B. Thus, we confirmed that orf165 influenced CMS in pepper.

The comparison of four mitochondrial genomes reveals cytoplasmic male sterility candidate genes in cotton

BACKGROUND

The mitochondrial genomes of higher plants vary remarkably in size, structure and sequence content, as demonstrated by the accumulation and activity of repetitive DNA sequences. Incompatibility between mitochondrial genome and nuclear genome leads to non-functional male reproductive organs and results in cytoplasmic male sterility (CMS). CMS has been used to produce F₁ hybrid seeds in a variety of plant species.

RESULTS

Here we compared the mitochondrial genomes (mitogenomes) of Gossypium hirsutum sterile male lines CMS-2074A and CMS-2074S, as well as their restorer and maintainer lines. First, we noticed the mitogenome organization and sequences were conserved in these lines. Second, we discovered the mitogenomes of 2074A and 2074S underwent large-scale substitutions and rearrangements. Actually, there were five and six unique chimeric open reading frames (ORFs) in 2074A and 2074S, respectively, which were derived from the recombination between unique repetitive sequences and nearby functional genes. Third, we found out four chimeric ORFs that were differentially transcribed in sterile line (2074A) and fertile-restored line.

CONCLUSIONS

These four novel and recombinant ORFs are potential candidates that confer CMS character in 2074A. In addition, our observations suggest that CMS in cotton is associated with the accelerated rates of rearrangement, and that novel expression products are derived from recombinant ORFs.

Tapetal-Delayed Programmed Cell Death (PCD) and Oxidative Stress-Induced Male Sterility of Aegilops uniaristata Cytoplasm in Wheat

Cytoplasmic male sterility (CMS) plays a crucial role in the utilization of hybrid vigor. Pollen development is often accompanied by oxidative metabolism responses and tapetal programmed cell death (PCD), and deficiency in these processes could lead to male sterility. Aegilops uniaristata cytoplasmic male sterility (Mu-CMS) wheat is a novel male-sterile line in wheat, which possess important potential in hybrid wheat breeding. However, its CMS mechanisms remain poorly understood. In our study, U87B1-706A, with the Aegilops uniaristata cytoplasm, and the maintainer line 706B were used to explore the abortive reason. Compared with 706B, histological analysis and PCD detection of the anther demonstrated that U87B1-706A appeared as delayed tapetal PCD as well as a disorganized organelle phenotype in the early uninucleate stage. Subsequently, a shrunken microspore and disordered exine structure were exhibited in the late uninucleate stage. While the activities of antioxidase increased markedly, the nonenzymatic antioxidant contents declined obviously following overacummulation of reactive oxygen species (ROS) during pollen development in U87B1-706A. Real-time quantitative PCR testified that the transcript levels of the superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) genes, encoding pivotal antioxidant enzymes, were up-regulated in early pollen development. Therefore, we deduce excess ROS as a signal may be related to the increased expression levels of enzyme genes, thereby breaking the antioxidative system balance, resulting in delayed tapetal PCD initiation, which finally led to pollen abortion and male sterility in U87B1-706A. These results provide evidence to further explore the mechanisms of abortive pollen in CMS wheat.

Involvement of a universal amino acid synthesis impediment in cytoplasmic male sterility in pepper

To explore the mechanisms of pepper (Capsicum annuum L.) cytoplasmic male sterility (CMS), we studied the different maturation processes of sterile and fertile pepper anthers. A paraffin section analysis of the sterile anthers indicated an abnormality of the tapetal layer and an over-vacuolization of the cells. The quantitative proteomics results showed that the expression of histidinol dehydrogenase (HDH), dihydroxy-acid dehydratase (DAD), aspartate aminotransferase (ATAAT), cysteine synthase (CS), delta-1-pyrroline-5-carboxylate synthase (P5CS), and glutamate synthetase (GS) in the amino acid synthesis pathway decreased by more than 1.5-fold. Furthermore, the mRNA and protein expression levels of DAD, ATAAT, CS and P5CS showed a 2- to 16-fold increase in the maintainer line anthers. We also found that most of the amino acid content levels decreased to varying degrees during the anther tapetum period of the sterile line, whereas these levels increased in the maintainer line. The results of our study indicate that during pepper anther development, changes in amino acid synthesis are significant and accompany abnormal tapetum maturity, which is most likely an important cause of male sterility in pepper.