Light perception in plants: cytokinins and red light join forces to keep phytochrome B active.

Plant growth and development is modulated by internal cues such as rhe hormonal balance and external factors. Plants are particularly sensitive to their light environment, which they scrutinize with at least three classes of photoreceptors. In recent years, it has become increasingly clear that light and hormonal signaling interact at several levels. A cytokinin receptor was recently identified together with several elements acting in this signaling pathway. ARR4, a response regulator working downstream of a cytokinin receptor, has been shown to regulate phytochrome B-mediated light signaling.