Glycerol is a polyol that is responsible for the cold hardiness of insects. Glycerol kinase gene, which is an important key enzyme for glycerol biosynthesis, was predicted from whole genome sequencing data from the diamondback moth, Plutella xylostella. Four of P. xylostella glycerol kinase genes (PxGKs) were determined as a functional glycerol kinase through in silico study. Pre-exposure of P. xylostella larvae to 4°C for 7 h significantly enhanced survival (rapid cold hardiness: RCH) under a freezing temperature (-10°C) and increased glycerol titers. To determination of functional GK gene, expressions of all GK genes were measured by RT-PCR analysis. All GK genes were expressed in all larval stage and tissues (gut, hemocyte, and fat body). Expressions of all GK genes were suppressed by its specific dsRNA treatment into 4 th instar larva. Each 150 ng of dsRNA PxGK2 treatment significantly decreased glycerol amount in hemolymph by HPLC analysis. Larval treated by dsRNA PxGK2 also significantly lost the RCH under -10°C exposure. These results indicate that glycerol is a crucial RCH agent and its synthesis is regulated by a specific PxGK2 gene among GK gene isoforms in P. xylostella. In addition, the beet armyworm, Spodpotera exigua, encodes RCHassociated SeGK1, which has been functionally identified by RNA interference.

• Youngjin Park(Department of Bioresource Sciences, Andong National University, Andong 760-749, Korea)
• Younggyun Kim(Department of Bioresource Sciences, Andong National University, Andong 760-749, Korea)