Arachis cysteine protease–cystatin complex modeling also suggested the interaction between cysteine protease and cystatin. The present study was, therefore, undertaken to confirm the possible interaction between the cysteine protease and its inhibitor cystatin in planta by co-expressing both the genes at same developmental stages in tapetal cell layer for proper inhibition
of cysteine protease. Similar strategy was used earlier to drive the Beta-Lapachone
of barstar, a ribonuclease inhibitor, for restoration of male fertility in transgenic male sterile plants expressing a cytotoxic protein, barnase from the bacterium, Bacillus amyloliquefaciens  and . Hence, we have used tapetum specific promoter, TA29 to drive the expression of the cysteine protease and its inhibitor for fertility restoration in the hybrid plants obtained by crossing the male sterile plants with the pollen from the plants expressing the inhibitor. We have prepared a construct using cystatin of A. diogoi and expressed it in the tapetal cell layer like the cysteine protease. Putative transgenic plants expressing cystatin were raised and confirmed through PCR. Transcript analysis was performed on PCR confirmed plants and three high expression
hemizygous transgenic plants were selected for exploring the possibility of restoring fertility on the male sterile plants expressing the cysteine protease in the tapetal tissues reported earlier . Since, the crossing is between cysteine protease expressing hemizygous male sterile plants and the hemizygous primary transgenic plants expressing cystatin in tapetum, it could be easily analyzed in genetic terms with respect to appropriate gene segregation and independent assortment.