Phytochrome Regulation of Branching in Arabidopsis

SCOTT A. FINLAYSON; SRIRAMA R. KRISHNAREDDY; TESFAMICHAEL H. KEBROM; JORGE J. CASAL

PLANT PHYSIOLOGY.

AMER SOC PLANT BIOLOGISTS

Año: 2010 vol. 152 p. 1914 - 1927

0032-0889

The red light:far-red light ratio perceived by phytochromes controls plastic traits of plant architecture, including branching.Despite the significance of branching for plant fitness and productivity, there is little quantitative and mechanistic informationconcerning phytochrome control of branching responses in Arabidopsis (Arabidopsis thaliana). Here, we show that inArabidopsis, the negative effects of the phytochrome B mutation and of low red light:far-red light ratio on branching werelargely due to reduced bud outgrowth capacity and an increased degree of correlative inhibition acting on the buds rather thandue to a reduced number of leaves and buds available for branching. Phytochrome effects on the degree of correlativeinhibition required functional BRANCHED1 (BRC1), BRC2, AXR1, MORE AXILLARY GROWTH2 (MAX2), and MAX4. Theanalysis of gene expression in selected buds indicated that BRC1 and BRC2 are part of different gene networks. The BRC1network is linked to the growth capacity of specific buds, while the BRC2 network is associated with coordination of growthamong branches. We conclude that the branching integrators BRC1 and BRC2 are necessary for responses to phytochrome, butthey contribute differentially to these responses, likely acting through divergent pathways.