IDENTIFICATION AND EXPRESSION OF WATER STRESS-REGULATED AND ABSCISIC ACID-REGULATED GENES IN A DROUGHT-TOLERANT SUNFLOWER GENOTYPE

We have studied two lines of sunflower (Helianthus annuus L.) selected in the field as drought-tolerant (R1 genotype) or drought-sensitive ( S1 genotype). When subjected to drought conditions, the R1 line was ab le to maintain high leaf water potential longer and wilted later than the S1 line, Therefore, this indicates that R1 tolerance includes a le af-adaptive response. By subtractive hybridization, we have isolated s ix different cDNAs (designated sdi for sunflower drought-induced) corr esponding to transcripts accumulated in R1 and S1 leaves during adapti ve response. Analysis of transcript accumulation in response to drough t in both genotypes suggests a preferential expression of three sdi ge nes in the tolerant line. Abscisic acid-mediated induction, analysed i n R1 leaves, was observed for only four sdi genes. Sequence analysis o f six sdi clones revealed that five clones were related to known prote ins including non specific lipid transfer proteins (nsLTP), early ligh t-induced proteins (ELIP), 1-aminocyclopropane-1-carboxylate oxidase ( ACC oxidase) or dehydrins, predicted to be involved in a wide range of physiological processes.