PHYTOCHROME-INDUCED INTERCELLULAR SIGNALING ACTIVATES CAB-LUCIFERASE GENE-EXPRESSION

The phytochrome-induced expression pattern of the chlorophyll a/b bind ing protein (cab) gene was studied using a cab2::luciferase reporter t ransgene in the tobacco cotyledon. The role of developmentally regulat ed competence, cooperativity among cells and signal propagation was in vestigated by red-light microbeam irradiation of distinct areas of the cotyledon. Even with a minimal fluence, the response was not restrict ed to the irradiated cells. Following irradiation of the cotyledon bas e, the luciferase activity revealed a robust propagation of activating signals to areas that had not received a light stimulus. The acropeta l outspread formed distinct expression patterns depending on the site of the irradiation, The combination of imaging luciferase activity in living seedlings and microbeam microscopy provides significant experim ental evidence of how cellular light perception and intercellular sign alling contribute to the cab gene expression pattern.