GENES WITH HOMOLOGY TO FUNGAL AND S-GENE RNASES ARE EXPRESSED IN ARABIDOPSIS-THALIANA

The only RNase genes that have been cloned from higher plants are those expressed in species that are known to exhibit self-incompatibility, such as the S genes of Nicotiana alata. In this report, we investigated whether the expression of this particular type of RNase gene is restricted to self-incompatible species, or if similar genes are expressed in other plants. Using a polymerase chain reaction approach we have identified a set of three putative RNase genes in the self-compatible plant Arabidopsis thaliana (L.) Heynh. ecotype Columbia. These A. thaliana genes, designated RNS1, RNS2, and RNS3, do not cross-hybridize to each other, and their products are homologous to both the S-gene RNases of N. alata and a set of related fungal enzymes. The A. thaliana RNS1, RNS2, and RNS3 genes encode transcripts of 1.1, 1.3, and 1.1 kilobases, respectively, and of the three genes, RNS2 is the most highly expressed in whole plants. The identification of the RNS genes in a self-compatible species suggests that this class of RNases is of general significance in RNA catabolism in higher plants.