MYC2-Activated TRICHOME BIREFRINGENCE-LIKE 37 Acetylates Cell Walls and Enhances Herbivore Resistance.

O-acetylation of polysaccharides predominantly modifies plant cell walls by changing the physico-chemical properties and, consequently, the structure and function of the cell wall. Expression regulation and specific function of cell wall-acetylating enzymes remain to be fully understood. In this report we cloned a previously identified stunted growth mutant named sucrose uncoupled 1 (sun1) in Arabidopsis (Arabidopsis thaliana). SUN1 encodes a member of the TRICHOME BIREFRINGEN-LIKE family, AtTBL37. AtTBL37 is highly expressed in fast-growing plant tissues and encodes a Golgi apparatus-localized protein that regulates secondary cell wall thickening and acetylation. In sun1, jasmonate signaling and expression of downstream chemical defense genes, including VEGETATIVE STORAGE PROTEIN 1 (VSP1) and BRANCHED-CHAIN AMINOTRANSFERASE4 (BCAT4), are increased but, unexpectedly sun1 is more susceptible to insect feeding. The central transcription factor in jasmonate signaling, MYC2, binds to and induces AtTBL37 expression. MYC2 also promotes the expression of many other TBLs. Moreover, MYC activity enhances cell wall acetylation. Overexpression of AtTBL37 in the myc2-2 background reduces herbivore feeding. Our study highlights the role of O-acetylation in controlling plant cell wall properties, plant development and herbivore defense.