Mitochondrial GPATs protect Arabidopsis from water stress by impacting cuticle and secondary cell wall development.

Key message: Mt-GPAT1/2 are involved in cutin biosynthesis and negatively regulate SCW formation by modulating the lignin and cellulose synthesis genes. Alterations in cuticle and SCW lead to plant water imbalance. Trichomes and cuticles are critical epidermal adaptations that serve protective roles in plants. The cuticle functions as a barrier, allowing for controlled interactions between the plant and its environment. Cutin synthesis is crucial for plants to withstand various external stresses. In this study, we report on the Arabidopsis mutant gpat1 gpat2, which exhibits a highly permeable cuticle and defects in trichome development. Mutation of GPAT1 and GPAT2 resulted in a reduction of cutin monomer. In gpat1 gpat2, the structure of the cuticular layer of the cell wall is notably altered. Additionally, GPAT1 and GPAT2 are found to downregulate the expression of genes involved in lignin and cellulose biosynthesis, which are related to secondary cell wall (SCW) formation. The dysfunction of GPAT1 and GPAT2 disrupted the water balance of the plant. Our findings reveal a network where mitochondrial GPAT1 and GPAT2 play roles in maintaining water balance by participating in both Arabidopsis cutin synthesis and SCW formation.