Abstract 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.

Abstract The measurement of gene expression can provide important information about gene function and the molecular basis for developmental processes. We analyzed the transcriptomes at three different developmental stages of pepper flower [sporogenous cell division, stage (B1); pollen mother cell meiosis, stage (B2); and open flower (B3)]. In the cDNA libraries for B1, B2, and B3: 82718, 77061, and 91491 unigenes were assembled, respectively. A total of 34,445 unigene sequences and 128 pathways were annotated by KEGG pathway analysis. Several genes associated with nectar biosynthesis and nectary development were identified, and 8,955, 12,182, and 23,667 DEGs were identified in the B2 vs B1, B3 vs B1, and B3 vs. B2 comparisons. DEGs were involved in various metabolic processes, including flower development, nectar biosynthesis, and nectary development. According to the RNA-seq data, all 13 selected DEGs showed similar expression patterns after q-PCR analysis. Sucrose-phosphatase, galactinol-sucrose galactosyltransferase, and sucrose synthase played very important roles in nectar biosynthesis, and CRABS CLAW could potentially be involved in mediating nectary development. A significant number of simple sequence repeat and single nucleotide polymorphism markers were predicted in the Capsicum annuum sequences. The new results provide valuable genetic information about flower development in pepper.

ABSTRACT Pepper is one of the most important vegetable crops in China. Consumers in China are increasingly demanding high quality pepper (Capsicum annuum L.) fruit. As in flood crops, natural disasters, such as flooding, might not only affect pepper yield, but also significantly impact fruit quality. Thus, it is necessary to study the change in fruit quality under waterlogging stress and seek an improved method. Pepper '5901' was the experimental material; we investigated the effects of spraying exogenous Ca2+ on the photosynthetic characteristics and quality of pepper plants under waterlogging stress. We found that waterlogging significantly reduced the photosynthesis rate (PN), stomatal conductance (g s), fruit length, individual fruit diameter, individual fruit fresh weight, and soluble protein, soluble sugar, free amino acid, P, Fe, vitamin C (Vc), and vitamin E (Ve) contents. It significantly decreased the expression levels of 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO-1), catalase (CAT-2), and pyruvate kinase (PK) genes, and it significantly increased intracellular CO2 concentration, capsaicin content, and the expression level of the alcohol dehydrogenase-1 (ADH-1) gene. The parenchymatous cells in the root system and stem were loosely arranged, the degree of lignification was deepened, leaves became thinner, and palisade tissue thickness was reduced. Exogenous Ca2+ significantly enhanced capsaicin content, alleviated the extent of the reduction in the abovementioned physiological parameters, and maintained epithelial cell shape in the mesophyll layer. It maintained the intactness of the cell wall in the root system, cell membrane, and pulp cavity; it also reduced cell injury and stimulated the expression levels of ACO-1, ADH-1, CAT-2, and PK genes. Compared to the normal control, expression levels of these genes increased by 52.03%, 99.48%, 40.78%, and 125.67%, respectively. The present study indicates that spraying exogenous Ca2+ can effectively alleviate injury to pepper plants caused by waterlogging stress and improve the quality of pepper fruit.