Engineering the AEG1 promoter from cotton to develop male sterile lines
This work reports on modifying the Upstream Regulatory Module (URM, 1.5 Kb region upstream of the open reading frame) of Anther Expressing Gene 1 (AEG1) from cotton to achieve anther specific activity. AEG1 was identified in a previous study aimed to isolate a promoter with tapetum specific activity. Such a promoter could then be used to express barnase and barstar genes for developing male sterile and restorer lines for hybrid seed production in cotton. The AEG1 URM was observed to be active in tapetum as well as in roots making it unusable to drive the expression of barnase gene. Analysis of the URM showed the presence of several root specific motifs. Two modified AEG1 URMs were developed, by removing or mutating these motifs and its activity checked in tobacco. The activity of one of the modified URMs, AEG1({Delta}Bmut) was restricted to the anther tissue as observed using the reporter gene {beta}-glucuronidase. The study also demonstrates that male sterile lines could be developed in tobacco using the AEG1({Delta}Bmut) URM to express the barnase gene. This work thus shows the possibility of engineering promoters to achieve tissue specificity and to develop male sterile lines in cotton.