The Mechanisms Of Physiology And Biochemistry Of PH₃ Resistance In Tribolium Castaneum (Herbst)

Tribolium castaneum (Herbst) is an important worldwide stored pest. Direct feeding on the host grain, enhances mould growth and excretion of hydroxyquinone compounds contaminates and causes damage to the grain. For more than 40 years, this species has shown its ability to develop resistance to insecticides and resistant strains have spread geographically, so that it remains as one of the major pests of stored products. Because of long-time use of PH3 to control T. castaneum, its resistance to PH3 is more and more serious, and economic loss caused is increasing gradually. Funded by the Program for New Century Excellent Talents in University (NCET-04-0854), this research was carried out by applying virous biochemical means to study about three energy sources and three detoxication enzymes in different stages of three kinds of T. castaneum (ABTC-S, HYTC-R, HSTC-R) with different PH₃ resistent level. The result is as follows:1. The relationship between energy sources and resistance to PH₃ in T. castaneumTo measure the content of three energy sources among different developmental stages in the PH₃ resistant and susceptible strains of T. castaneum by the methods of acetylacetone, anthrone-colorimetry and Coomassiebrilliant blue G-250. The result shows the content of three energy sources in susceptible strains are higher than two PH₃ resistant strains during mature and pupa stage. The reason may be that, on one hand, it's the cost of resistance; on the other hand, it has something to do with the inherited backgroud of the three strains of this research .But in larva stage, as to susceptible strain, its dissolveable protein is higher than the two resistant strains, and the assay of the contents in triacylglycerol and polysaccharide is lower than the two resistant strains. That maybe caused by the different larva periods between resistant and susceptible strains.2. The relationship between 2 kinds of hydrolytic enzymes and resistance to PH₃ in T. castaneum2.1 Comparison of main Biochemical properties of CarE between susceptible strain and PH3 resistant strains of T. castaneumIn this study, the activity and specific activity of CarE in two resistant strains is lower than susceptible strains, but there is no correlation between its specific activity and resistance fold.The study of CarE Michaelis-Menten constant (K_m) and maximal velocity (V_m) of three strains shows that the K_m and V_m of three different developmental stages of HSTC-R strains, and K_m and V_m of HYTC-R strains are higher than susceptible strains. The change shows that the affinity of CarE to substrate in two resistant strains has some decreases, and the catalytic ability increases. Moreover, the result of in vitro inhibition indicates that organic phosphorus medicine malaoxon can inhibit the CarE activity of larva and pupa of T. castaneum. The CarEs of the susceptible larva and pupa are the most sensitive to malaoxon, while the high resistant strain is the least sensitive to malaoxon, and low resistant strain is between the two strains. This is interrelated with their resistance levels, and it indicates that PH₃ resistance affects the ability to metabolize exogenous toxicants of T. castaneum to some extent.2.2 Comparison of main Biochemical properties of ACP and ALP between susceptible strain and PH3 resistant strains of T. castaneumThe results showed that, either the specific activity or K_m or V_m of ACP in HSTC-R is lower than susceptible strains and HYTC-R strains. It indicates that PH₃ resistance affects ACP's affinity and catalytic ability to substrate to some extent.During the research on ALP, it is found that activity, specific activity, K_m and V_m of the two resistant strains are still low in the whole. It indicates that PH₃ resistance indeed affects ALP greatly. However, the difference between the two resistant strains is not significant, so probably there are other factors affecting the properties of ALP.3. The relationship between GSTs and resistance to PH₃ in T. castaneumThe research shows that comparing with susceptible strain, the specific activity of GSTs in resistant strains of T. castaneum has some increases, but not too much , and the change dose not affected by resistance level. When the substrate is GSH, the K_m values of two resistant strain GSTs are hiher than susceptible strain, and so is the V_m. It indicates that the resistance caused by PH₃ induced certain change of GSTs.