Blue and red-light irradiance switching of nuclear- and chloroplast-encoded gene expression in Arabidopsis and Sorghum

Abstract

We have previously shown in maize chloroplasts an interaction between light quality and irradiance levels in control of the expression of genes associated with photosystem II, LHCP2 and psbA. Blue light decreased LHCP2 and increased psbA mRNA expression compared with red light of equal irradiance. Differences were irradiance related. Our present work examines irradiance and quality light regulation of LHCP2, psbA, rbcS, PEPCO and PPDK gene expression in two different species, Arabidopsis (C3) and Sorghum (C4) at different stages of development and shows that the blue light suppression of LHCP2 and enhancement of psbA gene expression also operates at 50 and 130 μmol m −2 s −1 total irradiance. It also shows that light quality effects on LHCP2 gene expression are dependent on the stage of development but those on psbA are not. Sequential light quality experiments indicate that chloroplast gene expression is plastic and responsive to the immediate environment. Switching effects of blue in red light during development in light mixtures with a constant irradiance (50 μmol m −2 s −1) are blue light irradiance regulated.