Characterisation of the ethanol-inducible alc gene expression system for transgenic plants

We describe a chemically induced gene control mechanism for plants based on the ALCR transcription factor and alcA promoter of Aspergillus nidulans, which we have called the aic system. Ethanol, the chemical inducer, is not toxic at levels required for induction, and can be applied to the plants by spraying, root drenching and addition to liquid growth media. The ale system is very sensitive to ethanol and the induction is rapid; 0.01% (1.7 mM) ethanol in liquid growth media initiates chloramphenicol acetyl transferase (CAT) reporter gene expression within 4 h, with maximal expression occurring after 4 days. In the complete absence of ethanol, there is no detectable expression of CAT, nor do we observe induction in plants subjected to wound, cold or drought stress, or following treatment with either salicylic acid or methyl jasmonate. However, extreme anoxia resulting in elevated levels of alcohol dehydrogenase activity in both roots and leaves gave substantial induction of CAT in leaves but not in roots. We believe that the ale system will have broad utility in the exogenous control of plant gene expression in pure science and that it also has considerable potential in agriculture.