Transcriptome analysis of a Physcomitrella patens pphk quadruple mutant.

The plant hormone ABA plays an important role in protecting plants from drought, and activation of the plant-specific kinases SnRK2 is essential for ABA signaling. Recently, we have identified ABA and abiotic stress-responsive Raf-like kinase (ARK) as an upstream kinase of SnRK2 in the Physcomitrella patens and Arabidopsis thaliana. ARK is thought to be activated by autophosphorylation. However, the mechanism by which ARK is autophosphorylated in response to ABA and osmostress is unclear. In previous study, PpARK interact with the ethylene receptor (ETR)-related sensor histidine kinase (HK) 5 in yeast two-hybrid assay, so we focused on the ETR-related HK as a regulator of ARK. Physcomitrella patens has 8 genes belonging to ETR-related HK and can be classified into two subgroups, PpHK5/13/20/24 and PpHK8/9A/9B/19. Quadruple mutant disrupting the four HKs in the subgroup to which HK5 belongs lost their response to ABA and osmostress. To gain insight into the role of ETR-related HK in ABA and osmostress responses in Physcomitrella patens, we performed transcriptome analysis of pphk quadruple mutant and WT plants with 10 micro M ABA or 0.4 M mannitol for 3 hours.