The barstar gene from Bacillus amyloliquefaciens encodes a specific ribonuclease inhibitor (barstar enzyme) expressed only in the tapetum cells of the pollen sac during anther development.

The barstar enzyme specifically inhibits barnase RNAse. Together, the barnase RNAse and the barstar form a very stable one-to-one complex, in which the RNAse is inactivated. As a result, when pollen from the restorer line is crossed to the male sterile line, the resultant progeny express the RNAse inhibitor in the tapetum cells of the anthers allowing hybrid plants to develop normal anthers and restore fertility.

Also, the barstar gene may be used to prevent the barnase RNAse from disrupting the development of bacteria in which the introduced DNA was prepared during the transformation process.