Laccase GhLac1 Modulates Broad-Spectrum Biotic Stress Tolerance via Manipulating Phenylpropanoid Pathway and Jasmonic Acid Synthesis

Abstract

Plants are constantly challenged by a multitude of pathogens and pests, which causes massive yield and quality losses annually. A promising approach to reduce such losses is to enhance the immune system of plants through genetic engineering. Previous work has shown that laccases (p-diphenol:dioxygen oxidoreductase, EC 1.10.3.2) function as lignin polymerization enzymes. Here we demonstrate that transgenic manipulation of the expression of the laccase gene <i>GhLac1</i> in cotton (<i>Gossypium hirsutum</i>) can confer an enhanced defense response to both pathogens and pests. Overexpression of <i>GhLac1</i> leads to increased lignification, associated with increased tolerance to the fungal pathogen <i>Verticillium dahliae</i> and to the insect pests cotton bollworm (<i>Helicoverpa armigera</i>) and cotton aphid (<i>Aphis gosypii</i>). Suppression of <i>GhLac1</i> expression leads to a redirection of metabolic flux in the phenylpropanoid pathway, causing the accumulation of JA and secondary metabolites that confer resistance to <i>V. dahliae</i> and cotton bollworm; it also leads to increased susceptibility to cotton aphid. Plant laccases therefore provide a new molecular tool to engineer pest and pathogen resistance in crops.