New insights of red light-induced development: Novel molecular aspects of phytochrome B action

The red/far-red light absorbing photoreceptors phytochromes regulate development and growth, and thus play an essential role in optimizing adaptation of the sessile plants to the ever changing environment. Our understanding of how absorption of a red/far-red photon by phytochromes initiates/modifies diverse physiological responses has been steadily improving. Research performed in the last five years has been especially productive, and led to significant conceptual changes about the mode of action of these photoreceptors. In this review we focus on the phytochrome B photoreceptor, the major phytochrome species active in light-grown plants. We discuss how its light-independent inactivation (termed dark/thermal reversion), post translational modification, including ubiquitination, phosphorylation, sumoylation as well as heterodimerisation with other phytochrome species modify red-light controlled physiological responses. Finally we discuss how photobiological properties of phyB enable this photoreceptor to function also as thermosensor.