Identification and characterization of two waterlogging responsive alcohol dehydrogenase genes (AdADH1 and AdADH2) in Actinidia deliciosa

Previous study showed that two alcohol dehydrogenase genes (ADHs) were significantly upregulated in roots of Actinidia deliciosa after treatment with waterlogging using Illumina sequencing technology. Those two ADH genes, named AdADH1 and AdADH2, were isolated from A. deliciosa in this study. QRT-PCR analysis showed that AdADH1 and AdADH2 expression levels were significantly increased in A. deliciosa after treatment with waterlogging, NaCl, 4 degrees C, and heat stresses, but not ABA and drought stresses. The changes of AdADH1 and AdADH2 expression levels during waterlogging were much higher than those during other stresses. We examined the response to abiotic stresses in transgenic Arabidopsis lines in which the A. deliciosa AdADH1 and AdADH2 genes were introduced under the control of a constitutive promoter, respectively. Overexpression of A. deliciosa AdADH1 or AdADH2 in Arabidopsis could enhance waterlogging tolerance at five week old seedlings. However, the function of AdADH1 for waterlogging resistance was much better than that of AdADH2. Arabidopsis overexpressing AdADH1 gene could enhance the resistance to cold stress at five week old seedlings, but AdADH2 could not. Overexpression of AdADH1 gene enhances the resistance to salt stress at the stage of seed germination and in seedlings, and overexpression of AdADH2 gene enhances the resistance to salinity stress at the stage of seed germination but not in seedlings. However, transgenic Arabidopsis overexpressing AdADH1 or AdADH2 could not enhance to the osmotic stress at the stage of seed germination and in seedlings. These results indicated that A. deliciosa AdADH1 plays an important role in resistance to waterlogging, salinity, and cold stresses, but not drought stress, and AdADH2 plays an important role in resistance to waterlogging and salinity stresses, but not cold and drought stresses.