Male Sterility and Fertility Restoration in Transgenic Plants- During 1990-1992, an exciting example of producing transgenic plants with male sterility and fertility restoration. Genes has become available in Brassica napus. This should facilitate production of hybrid seed without manual emasculation and controlled pollination as often practiced in maize.

In 1990, C. Mariani and others from Belgium, successfully used a gene construct having an anther specific promoter (from TA29 gene of tobacco) and bacterial coding sequence for a ribonuclease (barnase gene from Bacillus amyloliquefaciens) for production of transgenic plants in B. napus.
The results were spectacular in the sense that the transferred gene prevented normal pollen development leading to male sterility. The product of barnase gene is cytotoxic, killing the tapetal cells, thus preventing pollen development. Utilizing this male sterility barnase gene construct (TA-29- RNase), it was possible to introduce male sterility in other crops also.

When transgenic male sterile plants (with barnase gene) were crossed with transgenic male fertile plants (with barstar gene), the F₁ plants expressed both genes so that male fertility was restored due to suppression of cytotoxic ribonuclease activity in the anther by the formation of cell specific RNase/RNase inhibitor complexes. This system of transgenic plants should facilitate hybrid seed production in crop plants in general.