Canadian Forest Service Publications
Characterization of horizontally transferred ß-fructofuranosidase (ScrB) genes in Agrilus planipennis. 2014. Zhao, C.; Doucet, D.; Mattapalli, O. Insect Molecular Biology 23: 821-832.
Issued by: Great Lakes Forestry Centre
Catalog ID: 35715
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The emerald ash borer (Agrilus planipennis) is an important invasive insect pest of Fraxinus spp. that feeds on host tissues containing high levels of sucrose. However, little is known about how it digests sucrose. Here, using larval midgut transcriptome data and preliminary genome sequence efforts, two β-fructofuranosidase-encoding ScrB genes, AplaScrB-1 and AplaScrB-2, were identified, and proved to reside within the A. planipennis genome. Homology and phylogenetic analysis revealed that they were acquired by A. planipennis via horizontal gene transfer (HGT) from bacteria, possibly an event independent from that reported in bark beetles (eg ScrB genes). Microsynteny between A. planipennis DNA scaffold #2042940, which hosts AplaScrB-1, and a region in the Tribolium castaneum chromosome LG4 suggested that A. planipennis gained this gene after the separation of Buprestidae and Tenebrionidae. Although both of the putative AplaScrB proteins have conserved β-fructofuranosidase motifs, only AplaScrB-2 was predicted to be a secretory protein. Expression of AplaScrB-1 seemed constitutive during development and in all tissues examined, whereas AplaScrB-2 showed a peak expression in adults and in the midgut. We propose that acquisition of these genes by A. planipennis from bacteria is adaptive, and specifically AplaScrB-2 is involved in breaking down dietary sucrose to obtain energy for development
Plain Language Summary
The emerald ash borer (EAB) is an important alien invasive insect pest of ash in North America. Much of the damage caused by EAB is the result of larvae carving galleries in cambial tissues located underneath the bark of the trunk and major branches, thereby blocking the flow of nutriments to various parts of the tree. Devising strategies and control products to mitigate the damage caused by EAB larvae requires an intimate knowledge of the pests’ nutritional physiology. This paper describes the discovery of two EAB digestive enzymes, the β-fructofuranosidases AplaScrB-1 and AplaScrB-2, which are involved in the breakdown of host tree sucrose into glucose and fructose. The genes coding for both enzymes were cloned and analysis of their sequences indicates that they may have been acquired from bacteria, via a process called “horizontal gene transfer”. The AplaScrB-1 gene was expressed in all larval tissues, while AplaScrB-2 gene was expressed at higher levels in the digestive tract. We propose that acquisition of these two genes by EAB from bacteria is adaptive, and specifically AplaScprB-2 is involved in breaking down dietary sucrose to obtain energy for development.