Work

Phosphorylation of BLUS1 kinase by phototropins is a primary step in stomatal opening

Year: 2013

Type: article

Abstract: Opening of stomata in the plant facilitates photosynthetic CO2 fixation and transpiration. Blue-light perception by phototropins (phot1, phot2) activates the plasma membrane H+-ATPase, causing stomata to open. Here we describe a regulator that connects these components, a Ser/Thr protein kinase, BLUS1 (BLU E LIGHT S IGNALING 1), which mediates a primary step for phototropin signalling in guard cells. blus1 mutants identified by infrared thermography result in a loss of blue light-dependent stomatal opening. BLUS1 encodes a protein kinase that is directly phosphorylated by phot1 in vitro and in vivo at Ser-348 within its C-terminus. Both phosphorylation of Ser-348 and BLUS1 kinase activity are essential for activation of the H+-ATPase. blus1 mutants show lower stomatal conductance and CO2 assimilation than wild-type plants under decreased ambient CO2. Together, our analyses demonstrate that BLUS1 functions as a phototropin substrate and primary regulator of stomatal control to enhance photosynthetic CO2 assimilation under natural light conditions. Blue light stimulates stomatal opening in Arabidopsis by activating phototropins. By screening for mutants that lack this response, the authors isolate the protein kinase blus1, and show that its phosphorylation by phototropin-1 promotes guard cell signalling and stomatal opening.

Source: Nature Communications

DOI: 10.1038/ncomms3094