Barnase-barstar system: an indelible technique to produce hybrid seeds in self-pollinated crops

Self-pollinated crops are sensitive to exploit high level of heterosis. The improvement of crop plants through the production of hybrid varieties is a major goal of plant breeding. The genetically engineered techniques have a pivotal role in developing male sterility and restorer systems. Chimaeric ribonuclease gene (barnase) expression within the anther selectively destroys the tapetal cell layer that surrounds the pollen sac, prevents pollen formation and leads to male sterility. A chimaeric tapetal cell-specific ribonuclease inhibitor gene (barstar) was used in male fertile plants to restore male fertility in F₁ progeny. Cytotoxic ribonuclease activity in the anther was suppressed to restore male fertility in F₁ hybrid by the formation of cell-specific RNase/RNase inhibitor complexes.