Induction of thaumatin-like proteins (TLPs) in Rhizoctonia solani-infected rice and characterization of two new cDNA clones.

Thaumatin-like proteins (TLPs) were shown to be induced in rice plants (cv. IR58) that were infected with the sheath blight fungus, Rhizoctonia solani. Western blot analysis revealed the presence of two TLPs with sizes of 25 and 24 kDa which are different from a previously reported TLP with a size of 15.6 kDa from rice plants infiltrated with the non-pathogenic bacterium, Pseudomonas syringae pv. syringae. By probing a cDNA expression library prepared from RNA isolated from R. solani-infected rice plants with a TLP antibody, several putative TLP cDNA clones were isolated and sequenced. The cDNA clones appeared to be derived from two different genes which shared only 77% sequence identity with each other and a lower percentage of sequence identity with the previously reported TLP cDNA clone. Southern blot analysis with the two TLP cDNAs revealed different rice genomic DNA fragments. Northern blot analysis also confirmed that a 1.1-kb RNA detectable by the TLP cDNA inserts was induced by fungal infection. Thus rice TLPs are encoded by a family of at least three genes which are differentially expressed in responses to bacterial or fungal pathogens.