Identification and Functional Analysis of Two Alcohol Dehydrogenase Genes Involved in Catalyzing the Reduction of ()-3-Hexenal into ()-3-Hexenol in Tea Plants ().

Alcohol dehydrogenase (ADH) is a vital enzyme in the biosynthesis pathway of six-carbon volatiles in plants. However, little is known about its functions in tea plants. Here, we identified two genes ( and ). An protein expression assay showed that both CsADH1 and CsADH2 proteins can catalyze the reduction of ()-3-hexenal into ()-3-hexenol. Subcellular localization revealed that both CsADH1 and CsADH2 proteins were predominantly localized in the nucleus and cytosol. had high transcripts in young stems in autumn, while showed extremely high expression levels in stems and roots. The expression of was mainly downregulated under ABA treatment, while and transcripts were significantly lower under MeJA treatment at 12 and 24 h. Under cold treatment, transcripts first decreased and then increased, while demonstrated an almost opposite expression pattern. Notably, was significantly upregulated under simulated invasion. Gene suppression by antisense oligonucleotides (AsODNs) demonstrated that AsODN_ treatment significantly reduced transcripts and the abundance of ()-3-hexenol products. The results indicate that the two genes may play an important role in response to (a)biotic stresses and in the process of ()-3-hexenol biosynthesis.