Study On The Diapause Induction And Low Temperature Environment Adaptation Mechanism Of Leguminivora Glycinivorella(Mats)

Leguminivora glycinivorella belongs to an important pest of soybean in China.It has a specific feeding habit,which can cause huge economic losses to soybean cultivation and production when it breaks out.In Northeast China,the pest carry out diapause over winter in the form of mature larvae,and the diapause period was about 9 months.Therefore,whether the mature larvae can have the safe hibernation or not is an important factor affecting the number of population in the next year.Diapause is an effective ecological strategy for the over-wintering larvae of Leguminivora glycinivorella to adapt to the low temperature environment in Northeast China.However,there are few studies on the diapause of Leguminivora glycinivorella,and only some preliminary studies have been carried out from the ecological and physiological aspects of diapause.In order to improve the understanding of the diapause characteristics and the effect of its influencing factors,further explore the effect of diapause formation on the adaptability of the overwintering larvae of the pest population to the low temperature environment and its dynamic regulation process,and improve the level of prediction,forecast and comprehensive management for Leguminivora glycinivorella,the diapause and related physiological and biochemical mechanisms on the overwintering larvae of Leguminivora glycinivorella were studied in this paper.The results were as follows:1. Larval diapause of Leguminivora glycinivorella was sensitive to short photoperiod.With the shortening of light time,the diapause rate of larvae increased gradually;when the light time was shorter than 14h,all the larvae entered diapause;when the light time was longer than 16 h,the larvae could pupate normally.The critical photoperiod of diapause was 14.81 h.The low instar larvae of Leguminivora glycinivorella were more sensitive to short photoperiod?14L:10D?.The longer the time for the larvae that received continuous short photoperiod treatment was,the higher the diapause rate was.2. The larvae of short photoperiod entered diapause state under the induction of short photoperiod,and made physiological response to the low temperature environment in advance.The supercooling point?-19.204??and freezing point?-13.49??on diapause larvae?DL?of Leguminivora glycinivorella were lower than the supercooling point?-16.42??and freezing point?-11.22??of non-diapause larvae?NDL?,and there was a significant difference in their supercooling ability.The contents of total carbohydrates,glycogen,glycerol and other energy substances in DL were significantly higher than those in NDL.The contents of total carbohydrates and glycerol in DL were 2.17 times and 1.76 times of NDL,respectively.However,there was no significant difference in the contents of water and soluble protein between them.The activity of POD and CAT in DL was significantly higher than that in NDL,while the activity of SOD was slightly lower than that in NDL,but there was no significant difference.3,DL was more sensitive to low temperature than NDL for Leguminivora glycinivorella.After low temperature treatment,the supercooling points of DL and NDL decreased significantly,and the water content in the body decreased significantly.The content of total carbohydrates,glycogen and trehalose in DL and NDL increased after short-term low-temperature treatment?10?4h,5?4h?,but the increase of total carbohydrates and trehalose in DL was more significant at 5?4H;the content of trehalose in DL with long-term low-temperature treatment?5?24h?was 1.45 times higher than that in NDL.The activities of POD,CAT and SOD in DL were significantly increased,while those of POD and CAT in NDL were significantly increased,but there was no significant change in SOD activity.After long-term low-temperature treatment?5?24h?,the activity of POD in NDL were not significantly changed,the activity of CAT was significantly increased and the activity of SOD was decreased;the activity of POD in DL was decreased,the activity of CAT was increased and the activity of SOD activity did not change.4. The energy substance content,metabolic enzyme and protective enzyme activity in DL?Leguminivora glycinivorella?were different in different overwintering environment?-10?,-5?,0?,5?and 10??,showing dynamic adaptability in time series.In the diapause process of Leguminivora glycinivorella,the content of total carbohydrates decreased significantly with time,and the change trend of glycogen content was similar to that of total carbohydrates,while the change trend of trehalose was opposite to that of glycogen,keeping a high level.Glycerol content increased significantly at-10?.The content of sorbitol changed little.The protein content increased with the decrease of temperature.In the diapause process of Leguminivora glycinivorella,the changes of these small molecular substances were affected by diapause development and temperature,and the dynamic changes of their contents could reflect the cold tolerance of Leguminivora glycinivorella.The activities of sorbitol dehydrogenase?SH?,hexokinase?HK?,pyruvate kinase?PK?and alkaline phosphatase?AKP?decreased significantly in the early stage of diapause and kept at a low level.The activities of four metabolic enzymes were related to diapause development and temperature synergism.Through the regulation of related metabolic enzymes,the metabolism rate of Leguminivora glycinivorella was maintained at a low level,which improved the cold tolerance ability of Leguminivora glycinivorella.After low temperature treatment,the content of H₂O₂in DL increased,the activity of SOD decreased in the early stage of diapause,and then increased significantly,and the activity of CAT and POD fluctuated greatly.There were significant changes in the activity of three protective enzymes under different temperature and diapause time,indicating that the physiological changes of Leguminivora glycinivorella larvae were different during diapause,and the change range could be used as an important physiological index to measure the cold resistance of Leguminivora glycinivorella DL.5. High throughput sequencing platform?Illumina Hiseq?was used to carry out RNA-seq,sequence assembly and bioinformatics analysis for NDL and DL.39466 Unigenes with annotation information were obtained by sequencing.Through the alignment of NR database,it was found that in the whole gene sequences of Leguminivora glycinivorella,there were the most similar gene sequence compared with Microplitis demolitior,accounting for 9.33%.There were1383 differential genes between NDL and DL,among which 557 genes were up-regulated,826genes were down-regulated.In COG annotation analysis,the most genes were annotated into C:energy production and transformation,accounting for 17.94%;the 6 processes with the most differential genes distributed in GO database included cell process?9.68%?,metabolic process?11.64%?,cell membrane?18.94%?,cell membrane group?18.43%?,catalytic activity phase?19.36%?and binding?14.01%?.509 genes were mapped to 270 pathways in KEGG database.During the diapause of Leguminivora glycinivorella,the expression of genes related to lipid metabolism and oxidoreductase activity was significantly up-regulated,indicating that these genes may be involved in the diapause of Leguminivora glycinivorella.