Polygalacturonase causes lygus-like damage on plants: cloning and identification of western tarnished plant bug (Lygus hesperus) polygalacturonases secreted during feeding

Abstract

Polygalacturonase (PG), an enzyme that degrades pectin within the plant tissue cell wall, has been postulated as the chemical cause of damage to plants by the mirid Lygus hesperus. Micro-injection of two pure recombinant Aspergillus niger PG II protein forms, the wild type enzymically active and the mutant inactive one, into alfalfa (Medicago sativa L.) florets, demonstrates that the enzymatic activity rather than the PG protein structure per se elicits damage symptoms. A PG gene family has been described for the tarnished plant bug, L. lineolaris. Here we report cloning members of the L. hesperus PG gene family, Lhpg2, obtained with L. lineolaris PG-specific primers and a novel Lhpg4, amplified with degenerate primers that were designed based, in part on the N-terminal sequence from an active, partially purified L. hesperus salivary gland PG protein. Proteomic analyses revealed that the salivary gland PGs encoded by Lhpg2 and Lhpg4 are detected in a diet into which L. hesperus has extruded its saliva when feeding.