COMPARISON OF THE GENETIC ORGANIZATION OF THE EARLY SALT-STRESS-RESPONSE GENE SYSTEM IN SALT-TOLERANT LOPHOPYRUM-ELONGATUM AND SALT-SENSITIVE WHEAT

Lophopyrum elongatum is a facultative halophyte related to wheat. Elev en unique clones corresponding to genes showing enhanced mRNA accumula tion in the early stages of salt stress were previously isolated from a L. elongatum salt-stressed-root cDNA library. The chromosomal distri bution of genes complementary to these clones in several genomes of th e tribe Triticeae and their copy number in the L. elongatum and wheat genomes are reported. Genes complementary to clones pESI4, pESI14, pES I15, pESI28, and pESI32 were found in homoeologous group 5, those comp lementary to pESI18 and pESI35 in homoeologous group 6, and those comp lementary to pESI47, pESI48, pESI3, and pESI2 in homoeologous groups 1 , 3, 4, and 7, respectively. The genes are present in a single copy pe r genome in L. elongatum with the exception of those complementary to pESI2 and pESI18 which are present in at least two and five copies, re spectively. Since similar copy numbers per genome were found in wheat (except for pESI2), the ability of L. elongatum to accumulate higher m RNA levels than wheat in response to salt shock apears to have evolved by changes in the regulation of these genes.