CHARACTERIZATION OF GLUCOSE‐INDUCED GLUCOSE OXIDASE GENE AND PROTEIN EXPRESSION IN Helicoverpa armigera LARVAE

Abstract

Caterpillar labial salivary enzyme glucose oxidase (GOX) plays an important role in plant-insect interactions by suppressing the caterpillar-induced nicotine production in tobacco plants. In the present study, we cloned and characterized the GOX gene (HaGox) from labial salivary glands of Helicoverpa armigera larvae using 3' and 5' RACE, homologous analysis, phylogenetic analysis, LC-MS/MS, and qRT-PCR. The deduced GOX amino acid sequence (606 amino acids) shares 99% and 76% identity with H. zea and Spodoptera exigua GOX, respectively, and is consistent with the GOX protein sequence identified from H. armigera labial salivary gland. These results confirmed that the HaGox encode the GOX protein. Transcript levels of HaGox in larval labial salivary glands were significantly higher than those in midgut and hemolymph, respectively, and those of caterpillars reared on tobacco leaves coated with 0.1%, 1%, and 10% glucose solutions were significantly higher than those reared on 0.01% glucose-coated leaves or control tobacco leaves. Western blot and native PAGE showed that GOX protein expression levels and GOX enzymatic activities also increased with dietary glucose. These results proved that GOX expressions in larval labial salivary glands induced by dietary glucose were exhibited not only on transcriptional levels, but also on translational/posttranslational levels.

Expressional divergence of insect GOX genes: From specialist to generalist glucose oxidase

“…This suggests that GOX transcripts and activity are regulated largely by carbohydrate content in H. assulta, but by carbohydrate and protein contents in H. armigera. Consistent with our finding, carbohydrates such as sucrose and glucose were found to increase GOX activities in H. armigera (Hu et al, 2008;Tang et al, 2012) and H. zea (Eichenseer et al, 2010). Likewise, carbohydrates and dietary protein were positively correlated with GOX activity in Spodoptera exigua (Babic et al, 2008), with the former affecting GOX's transcription, and the later effecting GOX's translational and/or posttranslational regulation (Afshar et al, 2010).…”

“…It is well known that GOX activity in herbivores' labial gland or oral secretion varies significantly, depending on developmental stages (Merkx-Jacques and Bede, 2005;Eichenseer et al, 1999), dietary factors (Hu et al, 2008;Tang et al, 2012;Afshar et al, 2010) and host plants (Peiffer and Felton, 2005;Eichenseer et al, 2010;Merkx-Jacques and Bede, 2005;Babic et al, 2008). However, it is not clear whether GOX activity is always higher in generalists than specialists at any comparable stages or conditions.…”

Glucose Oxidase of a Crucifer-Specialized Insect: A Potential Role in Suppressing Plant Defense via Modulating Antagonistic Plant Hormones

“…exigua, while GOX activity is determined by the dietary protein or amino acid levels . This characteristic seems to be common in generalist herbivores due to similar findings from Helicoverpa armigera . However, the greater GOX activity in generalist herbivores (H.…”

“…17 This characteristic seems to be common in generalist herbivores due to similar findings from Helicoverpa armigera. 18 However, the greater GOX activity in generalist herbivores (H. armigera) than in specialist (Helicoverpa assulta) is proved not to be a result of greater transcription rate, but possibly due to the better transcript stability, translation rate, enzyme stability, and/or their combination. 19 The mechanism of the GOX-mediated interaction in different insects varies and is not unique across different host plant types.…”

Cannibalism Affects Core Metabolic Processes in Helicoverpa armigera Larvae—A 2D NMR Metabolomics Study

“…d -glucono-1,5-lactone is an oxidation product of d -glucose. The reaction is carried out by glucose oxidase, an enzyme secreted in the labial salivary glands of H. armigera [ 12 ].…”