CHARACTERIZATION OF THE RICE PATHOGEN-RELATED PROTEIN RIRLA AND REGULATION OF THE CORRESPONDING GENE

In rice (Oryza sativa L.), local acquired resistance against Pyricular ia oryzae (Cav.), the causal agent of rice blast, can be induced by a preinoculation with the non-host pathogen Pseudomonas syringae pv. syr ingae. We have cloned a cDNA (Rir1a) and a closely related gene (Rir1b ) corresponding to transcripts that accumulate in leaf tissue upon ino culation with P. syringae pv, syringae. The cDNA encodes a putative 10 7 amino acid protein, Rir1a, that exhibits a putative signal peptide c leavage site in its hydrophobic N-terminal part and a C-terminal part that is relatively rich in glycine and proline. The Rir1b gene contain s a Tourist and a Wanderer miniature transposable element in its singl e intron and encodes a nearly identical protein. Rir1a is similar in s equence (ca. 35% identical and ca. 60% conservatively changed amino ac ids) to the putative Wir1 family of proteins that are encoded by patho gen-induced transcripts in wheat. Using antibodies raised against a Ri r1a-fusion protein we show that Rir1a is secreted from rice protoplast s transiently expressing a 35S::Rir1a construct and that the protein a ccumulates in the cell wall compartment of rice leaves upon inoculatio n with P. syringae pv. syringae. Possible roles of Rir1a in pathogen d efense are discussed.