Classification and expression diversification of wheat dehydrin genes.

Dehydrins (DHNs) are late embryonic abundant proteins characterized by the dehydrin domains that are involved in plant abiotic stress tolerance. In this study, fifty-four wheat DHN unigenes were identified in the expressed sequence tags database. These genes encode seven types of dehydrins (KS, SK3, YSK2, Y2SK2, Kn, Y2SK3, and YSK3) and separate in 32 homologous clusters. The gene amplification differed among the dehydrin types, and members of the YSK2- and Kn-type DHNs are more numerous in wheat than in other cereals. The relative expression of all of these DHN clusters was analyzed using an in silico method in seven tissue types (i.e. normal growing shoots, roots, and reproductive tissues; developing and germinating seeds; drought- and cold-stressed shoots) as well as semi-quantitative reverse transcription polymerase chain reaction in seedling leaves and roots treated by dehydration, cold, and salt, respectively. The role of the ABA pathway in wheat DHN expression regulation was analyzed. Transcripts of certain types of DHNs accumulated specifically according to tissue type and treatment, which suggests their differentiated roles in wheat abiotic stress tolerance.