RESPONSE OF THE MAIZE CATALASES TO LIGHT

The three maize catalase genes respond differentially to light signals . Expression of Carl is light independent while expression of Cat2 and Cad is light responsive. Upon exposure to light there is rapid accumu lation of CAT-2 protein in leaves, due to both increased transcript ac cumulation and increased translation of the Cat2 message. Short UV lig ht pulses also cause a strong transient induction of Cat2 gene express ion, while long term exposure to UV does not affect the rate of Cat2 t ranscription. The Cat3 gene of maize exhibits a transcriptionally regu lated circadian rhythm. The induction of the Cat3 circadian expression in etiolated leaves is probably regulated by a very low fluence phyto chrome response; the involvement of a blue light/UV-A and a UV-B photo receptor is also possible. Regulatory elements located on the Cat3 pro moter have recently been identified and their significance in the comp lex light response of the gene is being investigated. Possible physiol ogical role(s) of the light responding maize catalases Cat2 and Cat3 a re discussed. (C) 1997 Elsevier Science Inc.