Pollen-expressed S-RNases are not involved in self-incompatibility in Lycopersicon peruvianum

Abstract

 Self-incompatibility in solanaceous plants is gametophytically controlled by a multiallelic S-locus. The only known S-locus product is a series of extracellular ribonucleases (the S-RNases) which are expressed in the mature style and determine its self-incompatibility phenotype. Potentially, S-RNases also determine the self-incompatibility phenotype of pollen as some solanaceous plants express this protein for a brief period during anther development. To test this, we first showed that the S₃-RNase of Lycopersicon peruvianum is expressed during anther development. We then transformed L. peruvianum plants with sense and antisense versions of the S₃-RNase coding region under the control of a pollen-specific promoter. Pollen from the transgenic plants accumulated S₃-RNase transcripts and the S₃-RNase protein was detected immunologically in the sense transgenic plants. However, neither the sense nor the antisense S₃-RNase constructs altered the self-incompatibility phenotype of pollen from the transgenic plants, demonstrating the S₃-RNase is not the pollen product of the S₃-allele.