Identification and expression analyses of two lotus (Nelumbo nucifera) dehydrin genes in response to adverse temperatures, ABA and IAA treatments

Dehydrins (DHNs) play imperative role in the stress tolerance of high plants. In this study, the YSK2-type DHN (NnDHNl) and SK 3 -type DHN (NnDHN2) were investigated. The putative NnDHN1 and NnDNH2 shared conserved S-segment as well as K-segment, with distinct isoelectric points, kinase selectivities and number of functional motifs. Phylogenetic analysis revealed that NnDHNs were grouped with Y n SK n - and SK n -type of DHNs in high plants. Additionally, NnDHN1 mRNA was only expressed in leaves and embryo. NnDHN2 mRNA was found in embryo, leaves, rhizome and leafstalk. NnDHNs mRNAs were not detected in root of N. nucifera. Real-time PCR assay demonstrated that the levels of NnDHN1 and NnDHN2 mRNAs were significantly elevated during cold temperature, while both were relatively stable in response to high temperature. Moreover, NnDHN2 mRNA was significantly increased after treatment with abscisic acid (ABA) or indole-3-acetic acid (IAA), while NnDHN1 mRNA was induced by ABA treatment with little change in response to IAA. These results illustrate two NnDHNs with partially overlapping function which exhibit different stress responsiveness.