Minisymposium 20: Photomorphogenesis
Abs #
41001: Green light signals inform early plant development through a novel sensory system
Classical and contemporary studies show that green light (GL) signals can influence photomorphogenic development. Recent studies in our laboratory have shown that GL signals antagonize specific aspects of red-and blue-light-induced development during the transition from growth in darkness to growth in light. For instance, whereas red, far-red, blue and UV light inhibit stem elongation rate during de-etiolation, monochromatic GL causes the stem to elongate more rapidly. The response is rapid, obeys reciprocity, and is not mediated by known light sensors. Whole-genome microarray analyses performed on GL-pulse treated seedlings at a time coincident with maximal elongation rate indicated that a single, short GL pulse (102 μmol m-2) has specific effects on gene expression. Predictably, a GL pulse induces nuclear genes such as Lhcb and Elip through low-level activation of phytochrome A. However, the same arrays also show that a suite of plastid transcripts (many typically induced by light) is surprisingly down-regulated within 1 h of the treatment. A single low-fluence pulse of GL (102 μmol m-2) is sufficient to drive plastid transcript down-regulation within 15 minutes, matching the time/fluence parameters of the stem-growth response. These undocumented simultaneous GL responses occur after a brief GL treatment and are directly at opposition to predicted light responses. One interpretation of these findings is that unidentified GL-sensor (or sensors) informs the developing seedling of photosynthetically-unfavorable light conditions leading to alternative regimes of growth and gene expression that create an enhanced state of etiolation.
