Rice alcohol dehydrogenase genes: anaerobic induction, organ specific expression and characterization of cDNA clones.

Anaerobiosis rapidly induces alcohol dehydrogenase (ADH), an enzyme of the fermentation pathway, in different parts of rice seedlings. After initiation of anaerobiosis, the activity of the enzyme increases linearly for 3 days or more. The ADH activity is anaerobically inducible even in mature rice leaves in contrast to maize which shows no induction in mature leaves. Rice ADH activity can also be induced by an auxin analog, 2,4-dichlorophenoxyacetic acid, under aerobic conditions. The experimental results show that anaerobiosis increases the ADH mRNA level, indicating that the ADH enzyme is regulated at the transcriptional level. Starch gel electrophoresis of a protein extract from rice shows 3 distinct forms of ADH. The amounts of the 3 forms vary with the organ, suggesting that the expression of ADH genes is organ-specific. Sequencing data show that the two different cloned cDNA copies of ADH mRNAs are derived from two different genes.