Both tobacco TA29 and sesame GN13 promoters provide anther-specific GUS expression in transgenic sesame (Sesamum indicum L.)

Abstract

Yield improvement is one of the most concerning areas of the "Queen of Oilseed" sesame (Sesamum indicum L.) for its successful commercialisation. Heterosis breeding is an alternate approach for improving sesame compared to the time- and labour-consuming conventional breeding. However, tedious hand emasculation and pollination processes restrict the implementation of commercial heterosis on sesame. The unavailability of male sterile, restorer, and maintainer lines further complicates the problem. Biotechnological gene manipulation can silence anther-specific vital gene(s) leading to male sterility. Anther-specific gene study is therefore crucial to reach such a goal. In this study, we have cloned two established anther-specific promoters: sesame SiBGproplus (hereafter GN13, NCBI accession no. KT246471) and tobacco TA29 (NCBI accession no. X52283) in the plant expression vector pCAMBIA2301 producing respective GN13::GUS and TA29::GUS chimeric vectors. We recovered putatively transgenic T0 sesame lines using conventional Agrobacterium-mediated transformation with 1.76% and 1.71% frequencies, respectively. The T0 lines were segregated at the 3:1 Mendelian segregation ratio for kanamycin resistance and generated T1 transgenic lines by self-fertilisation. Most of the T1 transgenics had a single copy of transgene integration. The histological assay revealed the tapetum-specific GUS expression in the T1 transgenic lines; GUS expression was undetected in other tested plant parts. The results depict successful anther/tapetum-specific expression of two promoters in transgenic sesame lines. In further research, these promoters could be used for anther-specific cytotoxic gene expression, RNAi, or CRISPR-mediated mutational approaches to destroy androecium selectively and exhibit male sterility in sesame, resulting in heterosis-mediated improvement.