MOLECULAR CLONING AND CHARACTERIZATION OF ABA BIOSYNTHESIS GENES IN WILD BARLEY, Hordeum spontaneum

¹ Tubitak, Research Institute for Genetic Engineering and Biotechnology, 41470, Gebze, Kocaeli, Turkey

² Institute of Evolution, University of Haifa, Mount Carmel, Haifa, 31905, Israel

Abscisic acid (ABA) is a plant hormone that plays an important role in plant responses to various abiotic stresses such as drought. Our objective is to identify in natural populations of wild barley from across their ecogeographic range, including deserts, the physiological and genomic organization of drought resistance genes in terms of cloning and characterization of ABA biosynthesis genes. This work is focused on the ABA biosynthesis pathway, from zeaxanthin to ABA, as recent data provided evidence of their crucial contribution to the regulation of ABA biosynthesis. Molybdenum co-factor sulfurase (MoCo sulfurase), zeaxanthin epoxidase (ZEP), 9-cis-epoxycarotenoid dioxygenase (NCED), short chain dehydrogenase, reductase (SDR) and aldehyde oxidase (AOO3) genes have been cloned and sequenced in the genotypes of Hordeum spontaneum from a northern mesic Mediterranean area, semi-xeric steppes, and a southern xeric desert in Israel. The NCED gene, in particular, proposed to be the key regulatory gene in ABA biosynthesis, displays significant sequence polymorphism between genotypes. The southern blot analysis has been used to examine the genomic organization of the ABA biosynthesis genes and expression analyses of these genes will be performed. Development of an integrated strategy for cloning and characterization of ABA biosynthesis genes in wild barley will contribute to a better understanding of the regulation of ABA levels and this knowledge will then be helpful for future plant breeders to develop varieties more tolerant to drought stress.