An Alcohol Dehydrogenase Gene from Synechocystis sp. Confers Salt Tolerance in Transgenic Tobacco

Abstract

<i>Synechocystis</i> salt-responsive gene 1 (<i>sysr1</i>) was engineered for expression in higher plants, and gene construction was stably incorporated into tobacco plants. We investigated the role of Sysr1 [a member of the alcohol dehydrogenase (ADH) superfamily] by examining the salt tolerance of <i>sysr1</i>-overexpressing (<i>sysr1</i>-OX) tobacco plants using quantitative real-time polymerase chain reactions, gas chromatography-mass spectrometry, and bioassays. The <i>sysr1</i>-OX plants exhibited considerably increased ADH activity and tolerance to salt stress conditions. Additionally, the expression levels of several stress-responsive genes were upregulated. Moreover, airborne signals from salt-stressed <i>sysr1</i>-OX plants triggered salinity tolerance in neighboring wild-type (WT) plants. Therefore, Sysr1 enhanced the interconversion of aldehydes to alcohols, and this occurrence might affect the quality of green leaf volatiles (GLVs) in <i>sysr1</i>-OX plants. Actually, the <i>Z</i>-3-hexenol level was approximately twofold higher in <i>sysr1</i>-OX plants than in WT plants within 1-2 h of wounding. Furthermore, analyses of WT plants treated with vaporized GLVs indicated that <i>Z</i>-3-hexenol was a stronger inducer of stress-related gene expression and salt tolerance than <i>E</i>-2-hexenal. The results of the study suggested that increased C₆ alcohol (<i>Z</i>-3-hexenol) induced the expression of resistance genes, thereby enhancing salt tolerance of transgenic plants. Our results revealed a role for ADH in salinity stress responses, and the results provided a genetic engineering strategy that could improve the salt tolerance of crops.