Examining the role of trehalose in thermal tolerance by the whitefly Bemisia tabaci

The polyhydric alcohol sorbitol is known to function as a cryoprotectant in many insects, however, studies have shown that Bemisia tabaci produces sorbitol when under heat stress exceeding 30ºC. The presence of high rates of ketose reductase activity has indicated that fructose is the substrate for sorbitol synthesis. Fructose is also a component of the sucrose isomer trehalulose [α-D-glucopyranosl-(1,1)-β-D-fructofuranoside], which constitutes a major component of B. tabaci honeydew. It was predicted that trehalulose levels in honeydew should be reduced under high temperature conditions when fructose is instead converted to sorbitol in the body. Experiments were designed to examine the effect of temperature on sorbitol and trehalulose production by the whitefly using both pre-conditioned and short-term exposures to thermal variation between 26º and 40ºC. HPLC analysis of B. tabaci honeydew and whole body extracts revealed a negative relationship between trehalulose production in the honeydew and sorbitol accumulation in the whitefly body. This negative tradeoff suggests a role for trehalulose that responds to internal homeostatic demands under environmental variation.