RNase X2, a pistil-specific ribonuclease from Petunia inflata, shares sequence similarity with solanaceous S proteins.
Petunia inflata, a species with gametophytic self-incompatibility, has previously been found to contain a large number of ribonucleases in the pistil. The best characterized of the pistil ribonucleases are the products of the S alleles, the S proteins, which are thought to be involved in self-incompatibility interactions. Here we report the characterization of a gene encoding another pistil ribonuclease of P. inflata, RNase X2. Degenerate oligonucleotides, synthesized based on the amino-terminal sequence of RNase X2, were used as probes to isolate cDNA clones, one of which was in turn used as a probe to isolate genomic clones containing the gene for RNase X2, rnx2. The deduced amino acid sequence of RNase X2 shows 42% to 71% identity to the 20 solanaceous S proteins reported so far, with the highest degree of similarity being to S3 and S6 proteins of Nicotiana alata. The cDNA sequence predicts a leader peptide of 22 amino acids, suggesting that RNase X2, like S proteins, is an extracellular ribonuclease. Also, similar to the S gene, rnx2 is expressed only in the pistil, and contains a single intron comparable in size and identical in location to that of the S gene. However, rnx2 is not linked to the S locus, and, in contrast to the highly polymorphic S gene, it is monomorphic. The possible biological function of RNase X2 is discussed.
Lee
H S
HS
Department of Molecular and Cell Biology, Pennsylvania State University, University Park 16802.
Singh
A
A
Kao
T
T
D000595:Amino Acid Sequence; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D010944:Plants / Q000033:anatomy & histology / Q000201:enzymology*; D012260:Ribonucleases / Q000235:genetics*; D017386:Sequence Homology, Amino Acid
D010940:Plant Proteins; D004247:DNA; D012260:Ribonucleases; C078709:ribonuclease X2