Raf-like kinases and receptor-like (pseudo)kinase GHR1 are required for stomatal vapor pressure difference response

Significance With the continuing increase in global temperatures, plants transpire more water due to the increasing vapor pressure deficit. Stomatal pores in plants close rapidly in response to the rising vapor pressure deficit to counteract water loss. We demonstrate that mutations in the stomatal CO 2 signaling pathway do not impair the response to an increase in vapor pressure difference (VPD). Osmotic stress causes cytoplasmic Ca 2+ transients in guard cells. Nevertheless, we show that diverse investigated higher-order calcium-signaling mutants do not affect the VPD response. We reveal that B3 family Raf-like protein kinases and a plasma membrane receptor-like protein GHR1 function in the elusive leaf-to-air VPD-mediated stomatal closure pathway. Notably, ghr1 mutant alleles disrupt the classical “wrong-way” stomatal VPD response.