Submitted to: The Canadian Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2018
Publication Date: 4/15/2019
Citation: Jones, R.W. 2019. Plant vascular system-feeding Psyllidae (Hemiptera) and Nematoda genomes encode family 12 glycosyl hydrolases. The Canadian Entomologist. 151(3):291-297. https://doi.org/10.4039/tce.2019.11.
Interpretive Summary: Insect feeding on plants causes millions of dollars of loss each year. Damage is further increased when the feeding insect transmits a pathogen that infects the plant, greatly reducing yield and quality of annual crops such as potato and tomato, and resulting in permanent loss of production in various perennial crops such as grape and citrus. A new enzyme has been discovered in a group of insects that feed on plant fluids. This group of insects also transmit some of the most debilitating plant pathogens that infect crop plants. Identification of this enzyme allows for studies into how it may aid in maintaining insect feeding sites and in transmitting destructive plant pathogens. It also opens the possibility of selecting specific plant produced proteins that block the enzymatic activity, preventing both feeding and pathogen transmission. This information will be useful to scientists studying insect pathogen transmission, and for plant breeding efforts designed to optimize enzyme inhibitor protein production in plants.
Technical Abstract: Insect feeding takes many different forms, ranging from physical consumption of plant parts to removal of plant fluids through feeding on phloem or xylem vasculature. Physical consumption of plant parts has been shown to be facilitated by insect-encoded plant cell wall hydrolases, many of them cellulose-targeting glycosyl hydrolases from family 9. We now report the first evidence for genomic encoding of family 12 glycosyl hydrolases that have endoglucanase/xyloglucanase activity. The genes were identified in three psyllids (Acanthocasuarina meullerianae, Pachypsylla venusta and Diaphorina citri), the glassy-winged sharpshooter (Homalodisca vitripennis) and a root tip feeding nematode (Xiphinema index). While the final gene product was highly similar, the genomic intron structure varied, having a 2.5 kB intron in P. venusta, a 240 bp intron in D. ctri and no intron in H. vitripennis or X. index. Endoglucanase and xyloglucanase activity was demonstrated using the D. citri gene in an Agrobacterium-infiltration based expression system. The presence of GH family 12 in this set of insects suggests a specific role in facilitating feeding on phloem and xylem tissue, and the possible involvement in facilitating the vectoring of Xylella fastidiosa by H. vitripennis and Candidatus Liberibacter asiaticus by D. citri.