GSE123543
A pathogen-responsive gene cluster for the production of highly modified fatty acids in tomato
In response to biotic stress, plants produce suites of highly modified fatty acids that bear unusual chemical functionality. Despite their chemical complexity and proposed roles in pathogen defense, little is known about the biosynthesis of these decorated fatty acids in plants. Falcarindiol is a prototypical acetylenic lipid present in carrot, tomato, and celery that inhibits growth of fungi and human cancer cell lines. Using a combination of untargeted metabolomics and RNA sequencing, we discovered a biosynthetic gene cluster in tomato (Solanum lycopersicum) that is required for the production of falcarindiol in response to an adapted fungal pathogen, Cladosporium fulvum. By reconstituting the initial biosynthetic steps in a heterologous host (Nicotiana benthamiana) and generating transgenic pathway mutants in tomato, we demonstrate a direct role for three genes in the cluster in falcarindiol biosynthesis. This work reveals a mechanism by which plants sculpt their lipid pool in response to pathogens, and provides critical insight into the complex biochemistry of alkynyl lipid production. Overall design: Tomato (Solanum lycopersicum VF36, 4.5 week-old plants) were treated with a panel of fungal elicitors via leaf infiltration: chitin (Ct, 0.5 mg/ml), Malassezia restricta (Mz, OD600 = 0.5), Cladosporium fulvum (Cf, OD600 = 1.0), and a panel of bacterial elicitors: flg22 (Fg, 1 µM), Staphylococcus epidermidis (Sc, OD600 = 1.0), Propionibacterium acnes (Pb, OD600 = 1.0) and Xanthomonas euvesicatoria (Xe, OD600 = 0.2), and water (mock, control). After pathogen inoculation, leaves (one leaf from three individual plants per treatment, n=3) were collected at 12, 24, and 48 hours post-inoculation using razor, flash frozen by liquid nitrogen, and stored at -80 °C for later use in gene profiling and RNA-Sequencing.