gpat6a tomato infected with P.infestans

Most above ground parts of vascular plants are covered by an extracellular cuticle composed of cutin to protect against dehydration and to form a barrier against pathogen attack. Cutin monomers contain 16- or 18-carbon fatty acids and glycerol-3-phosphate acyltransferase enzymes (GPATs) transfer these fatty acids to glycerol, facilitating their transport to the plant surface. The GPAT6-like RAM2 gene has been shown to be important for full susceptibility of Medicago truncatula roots to the oomycete pathogen Phytophthora palmivora. Here we address the dual functionality of GPAT6 during development of the leaf wall to provide a barrier to pathogen entry and water loss. Silencing of NbGPAT6a increased leaf susceptibility to P. infestans, whereas stable overexpression of NbGPAT6a-GFP rendered leaves more resistant. Mutation (knockout) of the orthologous gene in Tomato (Microtom), SlGPAT6a, results in increased susceptibility of leaves to P. infestans infection but increased resistance to Botrytis cinerea. CryoSEM revealed that leaves of tomato gpat6 mutants feature a thicker but more porous cell wall/cuticle and contain fewer stomata.