The expression and anaerobic induction of alcohol dehydrogenase in cotton

The alcohol dehydrogenase (ADH) system in cotton is characterized, with an emphasis on the cultivated allotetraploid species Gossypium hirsutum cv. Siokra. A high level of ADH activity is present in seed of Siokra but quickly declines during germination. When exposed to anaerobic stress the level of ADH activity can be induced several fold in both roots and shoots of seedlings. Unlike maize and Arabidopsis, ADH activity can be anaerobically induced in mature green leaves. Three major ADH isozymes were resolved in Siokra, and it is proposed that two genes, Adh1 and Adh2, are coding for these three isozymes. The genes are differentially expressed. ADH1 is predominant in seed and aerobically grown roots, while ADH2 is prominent in roots only after anaerobic stress. Biochemical analysis demonstrated that the ADH enzyme has a native molecular weight of approximately 81 kD and a subunit molecular weight of approximately 42 kD, thus establishing that ADH in cotton is able to form and is active as dimers. Comparisons of ADH activity levels and isozyme patterns between Siokra and other allotetraploid cottons showed that the ADH system is highly conserved among these varieties. In contrast, the diploid species of cotton all had unique isozyme patterns.