Abstract
AbstractDiapause, an arrested period of postâembryonic development in insects, is under the control of hormonal interactions. In the bamboo borer Omphisa fuscidentalis Hampson (Lepidoptera: Crambidae), larvae remain in diapause for as long as 9 months during the dry season, from September to the following June, although the factors that regulate larval diapause are poorly understood. The present study describes the cloning and expression analysis of the diapause hormone and pheromone biosynthesis activating neuropeptide (DHâPBAN) precursor of O. fuscidentalis (OmpfuâDHâPBAN cDNA), aiming to reveal how it may be involved regulating larval diapause in this species in combination with environmental factors. The open reading frame (ORF) of the cDNA encodes a 199âamino acid precursor protein that contains DH, PBAN and three other neuropeptides, all of which share a conservative Câterminal pentapeptide motif FXPR/KL (X = G, T or S). The OmpfuâDHâPBAN is highly similar (74%) to the DHâPBAN of the legume pod borer (Maruca vitrata). A quantitative realâtime polymerase chain reaction reveals that OmpfuâDHâPBAN mRNA is expressed only in neural tissues and that expression is highest in the suboesophageal ganglion. In addition, the expression level of OmpfuâDHâPBAN mRNA in the suboesophageal ganglion is consistently high during the fifth larval instar, increasing moderately in early diapause before reaching a peak during late diapause. After pupation, expression of the OmpfuâDHâPBAN precursor decreases to a low level. In addition to endocrine factors, the results demonstrate that photoperiod increases the expression level of OmpfuâDHâPBAN mRNA in larval diapause. These results also suggest that the expression of the OmpfuâDHâPBAN gene correlates with larval diapause development and may be activated by photoperiod in O. fuscidentalis.
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