Sunlight-induced anthocyanin pigmentation in maize vegetative tissues

Although, in maize, sunlight-regulated anthocyanin formation in vegetative tissues is observed only in the cultivars harbouring homozygous recessive p i loci, the identity of the photoreceptor mediating this process is not yet fully established. In this study the nature of photoreceptor(s) mediating this response was examined using an Indian hybrid maize cultivar (Kanchan-5 21), The etiolated maize seedlings of this cultivar on exposure to sunlight formed anthocyanin in all vegetative organs. Sunlight elicited photoinduct ion of anthocyanin with a slow increase between 4-16 h after the sunlight e xposure, followed by a rapid increase between 16-24 h, The photoinduction o f anthocyanin was primarily mediated by the UV-B component of sunlight and could be elicited by exposure to an artificial UV-B light source. The sunli ght-mediated induction of anthocyanin was reduced if the sunlight exposure was terminated with a far-red pulse before transfer to darkness, indicating a coaction of phytochrome in this photoresponse, Exposure to sunlight also stimulated phenylalanine ammonia lyase (PAL) activity in all organs with t wo temporally separated peaks. The first peak of PAL between 4-12 h was ind uced by phytochrome, and the second peak of PAL between 12-24 h was induced by UV-B light. These results indicate that the photoinduction of anthocyan in in maize is mediated by a coaction of UV-B light and phytochrome.