ER5, A TOMATO CDNA-ENCODING AN ETHYLENE-RESPONSIVE LEA-LIKE PROTEIN -CHARACTERIZATION AND EXPRESSION IN RESPONSE TO DROUGHT, ABA AND WOUNDING

We report the isolation by differential display of a novel tomato ethy lene-responsive cDNA, designated ER5. RT-PCR analysis of ER5 expressio n revealed an early (15 min) and transient induction by ethylene in to mato fruit, leaves and roots. ER5 mRNA accumulated during 2 h of ethyl ene treatment and thereafter underwent a dramatic decline leading to u ndetectable expression after 5 h of treatment. The full-length cDNA cl one of 748 bp was obtained and DNA sequence analysis showed strong hom ologies to members of the atypical hydrophobic group of the LEA protei n family. The predicted amino acid sequence shows 67%, 64%, 64%, and 6 1% sequence identity with the tomato Lemmi9, soybean D95-4, cotton Lea l4-A, and resurrection plant pcC27-45 gene products, respectively. As with the ether members of this group, ER5 encodes a predominantly hydr ophobic protein. Prolonged drought stress stimulates ER5 expression in leaves and roots, while ABA induction of this ethylene-responsive clo ne is confined to the leaves. The use of 1-MCP, an inhibitor of ethyle ne action, indicates that the drought induction of ER5 is ethylene-med iated in tomato roots. Finally, wounding stimulates ER5 mRNA accumulat ion in leaves and roots. Among the Lea gene family this novel clone is the first to display an ethylene-regulated expression.