D3027: A glucose-conjugating enzyme is highly expressed in the silk glands of moths

Uridine diphosphate glycosyltransferase (UGT) is a multigene family of enzymes responsible for catalyzing glycosylation of small hydrophobic molecules. These enzymes participate in the detoxification of xenobiotics and biotransformation of endobiotics, where glucose conjugation increases the water solubility of lipophilic aglycone compounds. Recently, a genomic analysis of the corn earworm (Helicoverpa zea), a serious agricultural pest species feeding on numerous economically important plants, identified 45 different UGT genes. We discovered a UGT gene (UGT34) showed high levels of expression exclusively in the silk gland tissue, a tissue which is not believed to be directly involved in detoxification, but was not expressed in the other tissues, such as central nervous system, guts, fat body, and Malpighian tubules. Quantitative and real-time PCR were used to analyze the expression levels of UGT34 in different instar stages and silk gland sub-segments, revealing that UGT34 is generally expressed at all instar levels and largely expressed in the middle and posterior subsegments of the silk glands. The soybean looper (Chrysodeixis includens), another Noctuidae moth species, was analyzed and found to have similar gene expression patterns, implying that UGT34 may play an important role in the silk glands of moths. This study used RNA interference (RNAi) but was revealed to be unsuccessful in determining UGT34 function. Silk plays a critical role in feeding, protecting, and metamorphosis in many lepidopteran insect species. Altogether, the present study implies that UGT34 plays an important role in silk glands, yet its molecular and physiological function needs to be determined by further study.