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Earlier, a pollen-specific Oryza sativa indica pollen allergen gene (OSIPA), coding for expansins/pollen allergens, was isolated from rice, and its promoter--upon expression in tobacco and Arabidopsis--was found active during the late stages of pollen development. In this investigation, to analyze the effects of different putative regulatory motifs of OSIPA promoter, a series of 5' deletions were fused to β-glucuronidase gene (GUS) which were stably introduced into rice and Arabidopsis. Histochemical GUS analysis of the transgenic plants revealed that a 1631 bp promoter fragment mediates maximum GUS expression at different stages of anther/pollen development. Promoter deletions to -1272, -966, -617, and -199 bp did not change the expression profile of the pollen specificity. However, the activity of promoter was reduced as the length of promoter decreased. The region between -1567 and -199 bp was found adequate to confer pollen-specific expression in both rice and Arabidopsis systems. An approximate 4-fold increase in the GUS activity was observed in the pollen of rice when compared to that of Arabidopsis. As such, the OSIPA promoter seems promising for generation of stable male-sterile lines required for the production of hybrids in rice and other crop plants.

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