A 163‐bp insertion in the Capana10g000198 encoding a MYB transcription factor causes male sterility in pepper (Capsicum annuum L.)

Abstract

SUMMARY Male sterility provides an efficient approach for commercial exploitation of heterosis. Despite more than 20 genic male sterile (GMS) mutants documented in pepper (Capsicum annuum L.), only two causal genes have been successfully identified. Here, a novel spontaneous recessive GMS mutant, designated msc‐3, is identified and characterized at both phenotypic and histological levels. Pollen abortion of msc‐3 mutant may be due to the delayed tapetum degradation, leading to the non‐degeneration of tetrads callosic wall. Then, a modified MutMap method and molecular marker linkage analysis were employed to fine mapping the msc‐3 locus, which was delimited to the ~139.91‐kb region harboring 10 annotated genes. Gene expression and structure variation analyses indicate the Capana10g000198, encoding a R2R3‐MYB transcription factor, is the best candidate gene for the msc‐3 locus. Expression profiling analysis shows the Capana10g000198 is an anther‐specific gene, and a 163‐bp insertion in the Capana10g000198 is highly correlated with the male sterile (MS) phenotype. Additionally, downregulation of Capana10g000198 in male fertile plants through virus‐induced gene silencing resulted in male sterility. Finally, possible regulatory relationships of the msc‐3 gene with the other two reported pepper GMS genes, msc‐1 and msc‐2, have been studied, and comparative transcriptome analysis reveals the expression of 16 GMS homologs are significantly downregulated in the MS anthers. Overall, our results reveal that Capana10g000198 is the causal gene underlying the msc‐3 locus, providing important theoretical clues and basis for further in‐depth study on the regulatory mechanisms of pollen development in pepper.

Key candidate genes for male sterility in peppers unveiled via transcriptomic and proteomic analyses

“…Furthermore, Dong et al. identified CaMYB80 as a key regulator gene specifically expressed in anthers, with its downregulation causing male sterility in pepper ( Dong et al., 2022 ). In wheat genetic breeding studies, CaPRXs were found to be upregulated during early pollen development ( Hiraga et al., 2001 ; Liu et al., 2018 ).…”

“…This finding indicates that CaPRX, identified via proteomics and transcriptomics in multiomics analysis, indirectly influence the process of male sterility in pepper. Furthermore, Dong et al identified CaMYB80 as a key regulator gene specifically expressed in anthers, with its downregulation causing male sterility in pepper (Dong et al, 2022). In wheat genetic breeding studies, CaPRXs were found to be upregulated during early pollen development (Hiraga et al, 2001;Liu et al, 2018).…”

“…Wang et al (2019) found that orf300a and orf314a were strong candidate genes for CMS in pepper via mitochondrial assembly of the sterile line 138A and maintainer line 138B. Another study documented more than 20 GMS mutants in pepper (Dong et al, 2022). Transcriptomic analysis of sterile (160S-male sterile (MS) and fertile (160S-MF) flowers of Brassica napus revealed that heat shock proteins, antioxidants, skeletal proteins, GTPase, and calmodulin might be involved in thermosensitive GMS (Tang et al, 2019).…”