Molecular cloning and functional analysis of pea cDNA E86 encoding homologous protein to hypersensitivity-related hsr203J

Clone E86 was isolated as cDNA for elicitor-inducible gene from pea epicotyls by differential screening. The deduced amino acid sequence of E86 showed high homology to hypersensitivity-related protein hsr203J in tobacco and also showed significant homologies to the Ser-active hydrolases, such as mammalian hormone-sensitive lipases, bacterial lipases and esterases. E86 polypeptide possesses consensus amino acid sequence motifs (His-Gly) and (Gly-X-Ser-X-Gly) conserved in lipases and esterases and showed esterase degradation of p-nitrophenyl butyrate. Northern blot analysis revealed that the E86-transcript is abundant in roots and stems and was induced by fungal elicitor in pea epicotyls. However, elicitor-induced accumulation of E86 mRNA was significantly inhibited by the fungal suppressor. Furthermore the expression of the genes encoding E86 and phenylalanine ammonia-lyase was induced within 1 h after the inoculation of a nonpathogen, but it was delayed for 5 h by the inoculation of a compatible pathogen. These results suggest that the elicitor-induced Ser-active hydrolase derived from E86 gene might be related to the plant defense responses.