PLDα1 and GPA1 are involved in the stomatal closure induced by Oridonin in Arabidopsis thaliana

Oridonin is an important diterpenoid, which plays an important role in plant growth and development. PLD alpha 1 and GPA1 are involved in many biotic or abiotic stresses. In this study, using the seedlings of Arabidopsis thaliana L. wild type (WT), PLD alpha 1 defective mutant (pld alpha 1), GPA1 defective mutant (gpa1) and pld alpha 1/gpa1 double mutant as materials, the effect of stomatal apertures responding to Oridonin and the functions of PLD alpha 1 and GPA1 in this response were investigated. The results showed that 60 mu mol.L-1 of Oridonin induced stomatal closure and significantly increased the relative expression levels of GPA1 and PLD alpha 1. Oridonin increased H2O2 accumulation in guard cells by inhibiting the antioxidant enzymes. The increase of H2O2 caused the expression of OST1, which is a positive regulatory gene for stomatal closure. Both PLD alpha 1 and GPA1 were involved in Oridonin-induced stomatal closure and PLD alpha 1 acted downstream of GPA1. The results suggested that Oridonin caused stomatal closure by affecting GPA1 and promoting PLD alpha 1 to produce PA, and further accumulating H2O2 to upregulate gene OST1.