Expression of self-incompatibility ribonucleases of Antirrhinum inEscherichia coli

Abstract

Self-incompatibility is an intraspecific reproductive barrier to prevent self-fertilization in the flowering plants. In many species, self-incompatibility is controlled by a single S locus with multiple alleles. So far, the only gene known in theS locus of the Solanaceae, Scrophulariaceae and Rosaceae encodes a class of ribonucleases, called self-incompatibility ribonucleases (S RNases), which have been shown to mediate stylar expression of self-incompatible reaction. As the first step to investigate their three-dimensional structure, we successfully expressed three biologically active S RNases of Antirrihnum (S ₂,S ₄ andS ₅) inEscherichia coli (E. coli). Their functional expressions caused no detrimental effect on host bacteria growth and provided a basis for a large scale preparation of S RNase proteins. Possible reasons for non-lethality of S RNases onE. coli are discussed.