Tapetum-specific expression of cysteine protease induces male sterility in tomato

Male sterile plants play a significant role in developing hybrid varieties to exploit the benefits of hybrid vigour in crops. Cysteine proteases play critical functions, including proteolysis and programmed cell death in plants. In this study, we have generated male-sterile transgenic tomato plants using AdCP (Arachis diogoi cysteine protease) gene under the control of a tapetum-specific promoter (TA-29). The transgenic tomato plants produced non-functional pollen grains. The aborted pollen grains of the male sterile plant did not germinate even after 24 h of incubation compared to normal pollen grains. PCR analysis confirmed the stable integration of transgenes in transgenic plants. Semi-quantitave RT-PCR analysis showed the tissue-specific AdCP gene expression in the anthers of transgenic tomato plants. A back-cross was conducted between the transgenic male-sterile plants (female parent) and control (untransformed) plants (male parent). The T1 progeny indicated the segregation into female fertile and male-sterile plants, showing normal fruit development and seed set. High levels of AdCP transcripts were detected in anther tissues, confirming tapetum-specific expression of the TA29 promoter. The male-sterile tomato plants with targeted expression of the AdCP gene in tapetum could potentially be used to develop novel varieties through hybrid seed production.