A GROUP 3 LEA CDNA OF RICE, RESPONSIVE TO ABSCISIC - ACID, BUT NOT TOJASMONIC ACID, SHOWS VARIETY-SPECIFIC DIFFERENCES IN SALT STRESS-RESPONSE

A cDNA clone oslea3, encoding a group 3 late-embryogenesis abundant (L EA) protein was isolated from roots of rice seedlings (Oryza sativa L. ). The encoded OSLEA3 protein has previously been found to accumulate to higher levels in roots of two salt-tolerant compared to a salt-sens itive rice variety in response to abscisic acid (ABA) [Moons et al., 1 995. Plant Physiol. 107, 177-186]. The OSLEA3 protein (M-r 20.5, pI 6. 5) characteristically contains ten imperfect 11-mer amino acid repeats . Exogenous application of ABA and exposure to salt shock (150 mM NaCl ) rapidly induces a de novo, abundant oslea3 transcript accumulation i n seedling roots, whereas application of jasmonic acid (9 mu M) does n ot induce oslea3 expression. The stress-induced oslea3 transcript grad ually declined upon prolonged salt shock, as wilting-induced damage be came irreversible. oslea3 expression was compared for the salt-toleran t variety Pokkali and the salt-sensitive cultivar Taichung N1. Higher maximal mRNA levels were found in roots of the tolerant variety, also declining less rapidly upon sustained salt shock, concomitant with a d elayed drop in shoot water content. DNA blot analysis indicated the ex istence of a small oslea3 gene family in rice with an equal gene numbe r in both ecotypes. The results suggest that a differential regulation of oslea3 expression is an aspect of the varietal differences in salt stress tolerance. (C) 1997 Elsevier Science B.V.