BLUS1 functions as a phototropin substrate and primary regulator of stomatal control

 

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

by Takemiya A., Sugiyama N., Fujimoto H., Tsutsumi T., Yamauchi S., Hiyama A., Tada Y., Christie J. M., Shimazaki K.-i. (2013)

in Nature Communications 4 – doi:10.1038/ncomms3094  –

Medline – http://www.nature.com/ncomms/2013/130628/ncomms3094/full/ncomms3094.html – 

https://www.nature.com/articles/ncomms3094

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 (BLUE LIGHT SIGNALING1), 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 CO₂assimilation under natural light conditions.