Studies on the molecular mechanism of HOS1-mediated phytochrome B function during hypocotyl growth of Arabidopsis

Abstract

During seedling development, response to light induces inhibition of hypocotyl elongation, cotyledon opening, and leaf greening, and those are called photomorphogenesis. For hypocotyl elongation, photoreceptors, especially one of the red/far-red light-sensing phytochromes, phytochrome B, is regarded as a crucial regulator of it. Although, it is not completely known how the phytochrome B regulates hypocotyl growth. Here, I showed that well known E3 ubiquitin ligase, HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 1, prevents the transcriptional activation activity of PHYTOCHROME INTERACTING FACTOR 4 which induces hypocotyl cell growth. Also, photoactivated phyB is needed for activation of HOS1 in inhibiting PIF4 activity. Consequently, I found a new molecular mechanism for the phyB-dependent prohibition of hypocotyl growth in Arabidopsis.