Regulation of input-output relationships in phytochrome A signalling.

CASAL, JORGE J.

Santiago de Chile

Simposio; II Reunión de Biología Vegetal; 2007

Light modulates plant growth and development. In particular, phytochrome A mediates two different photoresponses: the so-called very-low-fluence response (VLFR), which is required for germination when the seeds are briefly exposed to light during soil tillage, and the high-irradiance response (HIR), which is required for seedling de-etiotation and survival under dense plant canopies. The two response modes of phyA can be observed as discrete photobiological phases for some processes such as inhibition of hypocotyl growth and LHCB gene expression. The molecular mechanisms involved in the transition between the VLFR and the HIR with increasing frequency of phytochrome A excitation are not know. We will provide evidence in favour of a positive feed-back loop involving a transcription factor as a key component in the transition between VLFR and HIR.