Abstract
Pepper (Capsicum annuum L.) is a globally important horticultural crop. Use of the genic male-sterile (GMS) line enables efficient commercial hybrid pepper seed production. However, the mechanisms of pepper GMS functioning remain unclear. In this study, we used proteomic and transcriptomic analysis to identify proteins and genes related to genic male sterility. A total of 764 differentially expressed proteins (DEPs) and 1069 differentially expressed genes (DEGs) were identified in the proteomic and transcriptomic level respectively, and 52 genes (hereafter “cor-DEGs-DEPs” genes) were detected at both levels. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis identified 13 DEPs and 14 DEGs involved in tapetum and pollen development. Among the 13 DEPs identified, eight were involved in pollen exine formation, and they were all up-regulated in the fertile line 16C1369B. For the 14 DEGs identified, ABORTED MICROSPORES (AMS) and DEFECTIVE IN TAPETAL DEVELOPMENT AND FUNCTION1 (TDF1) were involved in tapetum development, and both are possibly regulated by Msc-1. All of these genes were detected and confirmed by qRT-PCR. The presence of these genes suggests their possible role in tapetum and pollen exine formation in GMS pepper. Most key genes and transcription factors involved in these processes were down-regulated in the sterile line 16C1369A. This study provides a better understanding of GMS (msc-1) molecular functioning in pepper.
Highlights
The use of male sterile lines to produce hybrid seeds is one of the most important methods in hybrid breeding; it is used, for instance, in crops such as rice, maize, Chinese cabbage, sunflower and pepper [1,2] The genic male sterile (GMS) pepper is a spontaneous male-sterile mutation found in Shenjiao (C. annuum) in China [3]
To determine the cause of anther sterility in 16C1369A, pepper anthers of the sterile line 16C1369A and the fertile line 16C1369B were selected at four different pollen developmental stages and paraffin section analysis was performed
At the pollen mother cell stage, the sterile 16C1369A and fertile line 16C1369B did not differ significantly in their cytological structure (Figure 1A,D), whereas pollen abortion was observed in the sterile line 16C1369A in the tetrad stage (Figure 1B,E); in this stage, the sterile line 16C1369A tapetal layer cells were over-vacuolized and premature death occurred, whereas in the fertile line 16C1369B, the tapetal layer cells were degraded sufficiently for microspore development
Summary
The use of male sterile lines to produce hybrid seeds is one of the most important methods in hybrid breeding; it is used, for instance, in crops such as rice, maize, Chinese cabbage, sunflower and pepper [1,2] The genic male sterile (msc-1) (GMS) pepper is a spontaneous male-sterile mutation found in Shenjiao (C. annuum) in China [3]. In Arabidopsis, several genes regulate the tapetum and its functions Among these genes, DYSFUNCTIONAL TAPETUM1 (DYT1) and ABORTED MICROSPORES (AMS) encode a bHLH transcription factor [17,20]; Mutations in these two genes can cause excessive tapetal expansion into the locule and result in sporophytic male sterility [20,21]. Liu et al [40] analyzed the anther transcriptomes in pepper CMS lines and its fertility restoration; they found that anther transcriptome analysis may be useful for identifying potential candidate genes associated with the formation or abortion of pollen. We use proteomic and transcriptomic analysis to identify the DEPs and DEGs in GMS (msc-1) pepper and its male fertile line at the key stage of pollen abortion. We discuss the relationship between these DEPs and DEGs and male sterility in GMS pepper, examine the possible biological functions of these DEPs and DEGs, and explore their potential effects on anther development and male sterility
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