| Rhabdoscelus lineaticollis is an invasive species of quarantine pest which was found in the southern China in recent years.For the invasive insect species,they have to adapt to the biotic and abiotic factors in the fresh environment for their sustainable development.Temperature,which often obviously affects the grown,survival and production of insect,is one of the key factors during its successful invasion.Under the field conditions,especially for the invasive species,insect can not avoid the unexpected exposure of extreme temperature with the global warming.Cumulative evidence has indicated that insect has developed some behavior and physilological adaption strategies to eleminate the negative influence of extreme temperature to some extent.However,the effects of extreme temperature exposure on R.lineaticollis and the potential physiological mechanism remain elusive.Here,we have demonstrated the effect of different temperature exposure on the life cycle,survival rate and reproduction of R.lineaticollis.Furthermore,the underlying physiological mechanisms were also detected by revealing the response pattern of heat shock protein genes and measuring the relative antioxidant enzyme activity.Our investigation will pave the way to predict the potential spreading tendency and development of new management strategy on this pest,The main results were as follows:1.Rhabdoscelus lineaticollis could complete its entire life cycle in the range of 18? to 30?.With the increasing temperature the period of its developmental stage shortened.However,at 30?,the duration of larval stage prolonged,which may be because the high temperature influence metabolic balance of larvae.Eggs could not hatch under the exposure of 12? or 13?.At 15?,the duration of larval stage could be up to one year,and R.lineaticollis could not complete the entire life cycle(without adult stage).The emerging rate of adult were the highest at 21? or 24?,suggesting that the optimum temperature for R.lineaticollis growth was in the range of 21? to 24?.2.RACE technique was used to clone three full-length cDNA of Rlhsp70,Rlhsc70 and Rlhsp90 in R.lineaticollis.BlastX showed that hsp70 and hsc70 had three signature sequences of the Hsp70 family,and Rlhsp90 had one signature sequence of the Hsp90 family.Phylogenetic tree analysis showed Rlhsp70 and Rlhsc70 clustered in different types,suggesting they descended from different ancestors.All these genes had closest genetic relationship to Coleoptera,which was consistent with the traditional taxonomy.3.After the exposure 2h of low temperature,the expression level of Rlhsp70 Rlhsc70 and Rlhsp90 were lower compared to the control,which showed that these three proteins didn't play an important role in cold tolerance.After the high temperature exposure for 2h,the expression levels of Rlhsp70 and Rlhsc90 were hundreds and dozens of times higher than that of the control,respectively,while the expression level of Rlhsc70 was lower.these results indicated that Rlhsp70 and Rlhsp90 may play an essential role in coping with heat injury.4.After the low temperature and high temperature exposure for 2h,the activities of CAT,SOD and POD showed different response to temperature variation.The activity of POD didn't appear to be affected by temperature compared to the control while activities of CAT and SOD increased remarkably at 39? and-7?.Furthermore,the CAT activity also increased significantly at 0? and 36?.These results suggested that the antioxidant enzymes may coordinate to protect larvae from thermal injury.In conclusion,the response of heat shock proteins and antioxidant enzymes in R.lineaticollis under the environment temperature stress is a kind of protective reaction to adapt temperature stress,which reveals the basic cause of the strong adaptability of bio-invasion from the molecular level and physical level. |
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