| Cnaphalocrocis medinalis(Guenée)is one of the most important pests on rice.It has a strong migratory ability.In recent years,the damage of C.medinalis has been increasing,and it has brought a huge threat to the safety of food production in our country.The outbreak of C.medinalis is sudden and depends to a largely extent on the migration population,so it brings great difficulty to the forecast and control.To clarify the occurrence and control mechanism of its migratory behavior is of great significance to the prediction and scientific prevention and control of the rice leaf folder.Take-off is the initial link of insect migration.The success of take-off directly determines the success or failure of insect migration.Proving the occurrence and regulation mechanism of migration and take-off behavior is the key to understanding the migration behavior of C.medinalis.Based on previous findings that the migratory take-off behavior of C.medinalis was dependent on light,this study conducted indoor observations on the take-off behavior of the field population of C.medinalis.Compare and analyze the effects of different light changes on the expression of cryptochromes-related genes(CRY1,CRY2)and juvenile hormone-related genes(JHAMT,Met)of the rice leaf folder,and the differences in the expression of these genes between migrants and residents.From the molecular perspective,we explored the molecular mechanism of light changes regulating the migratory take-off behavior of the rice leaf folder,and have some research progress.The main results are as follows:1.The take-off experiment of C.medinalis indoors.Using high-altitude searchlights to monitor the occurrence of C.medinalis in Jiangyan area of Jiangsu Province from 2017 to 2019 and dissection in the field,found that the dynamic inter-annual change trend of its occurrence in the region was the same,and in late August there was mostly emigration.After determining the emigration period based on the inter-annual dynamics,during the migration period of2019(August 28 to October 14),adults were collected from the field every day to observe the take-off behavior in the indoor simulated sunset light change environment.Found that the daily migratory take-off ratio was between 15% and 80%,the migratory take-off behaviors were concentrated at 19:00-20:00,and the peak take-off period was 19:00-19:30(within 30 minutes after the simulated sunset).Combined with previous studies,shown that light changes could induce the migratory take-off behavior of the rice leaf folder.2.The effect of light changes on the CRY1,CRY2,JHAMT,and Met of C.medinalis.Determining the expression of CRY1,CRY2,JHAMT and Met genes in adults by real-time fluorescent quantitative PCR(q PCR)to clarify the impact of light changes.Here,there were three schemes for light changes: constant light,instantaneous switching between light and dark(completely daken at 19:30),light and dark gradient(19:00-19:30 simulated sunset,19:30 completely dark).The research found:(1)In the same period,the expression levels of CRY1,CRY2,JHAMT and Met genes under different light change treatments were not completely the same.The expression level of CRY1 is only significantly different at 20:00;the expression level of CRY2 is significantly different at 19:30,19:45,and 20:00.The expression level of JHAMT is significant at 19:45;the expression level of Met was significantly different at 19:15,19:30.19:45 and 20:00.This indicated that light caused the differences in the expression levels of CRY1,CRY2,JHAMT and Met in the rice leaf folder,may not by its own biological rhythm.(2)Under light changes,the expression levels of CRY1,CRY2,JHAMT,and Met have significant differences in different periods.From 19:00 to 20:00,females’ CRY1 expression was the lowest at 19:15,and the highest at 19:30,males’ CRY 1 expression was highest at 19:30 and lowest at 20:00.The expression level of CRY2 in females was the lowest at 19:15 and 19:30 and highest at 20:00;and males’ CRY2 expression was highest at 19:30 and lowest at 19:45 and 20:00.Females’ JHAMT expression was highest at 19:15 and 19:30,and the lowest at 19:45 and 20:00;males’ JHAMT expression was lowest at 19:15 and highest at 19:45.Females’ Met expression was lowest at 19:15,highest at 19:45 and 20:00,males’ Met expression was highest at19:30,and lowest at 19:00 and 20:00.The above results indicated that light changes can cause changes in the expression of CRY1,CRY2,JHAMT,and Met in adults of C.medinalis,and the time point of the change is similar to the take-off peak period.(3)There was a significant correlation between the expression levels of CRY1,CRY2,JHAMT and Met in the adult C.medinalis.Under the light change treatment of the gradually dark before sunset group,the expression of CRY1 and CRY2 were significantly negatively correlated with the expression of JHAMT,and significantly positively correlated with the expression of Met.This indicated that under light changes,the cryptochrome-related genes CRY1 and CRY2 in the adult rice leaf folder could be involved in the regulation of the expression of juvenile hormone-related genes JHAMT and Met,thereby promoting the migration and take-off of the rice leaf folder.3.Expression differences of CRY1,CRY2,JHMAT,and Met in the migrants and residents C.medinalis.Using q PCR to determine the expression levels of CRY1,CRY2,JHAMT,and Met in the migrants and residents.The results showed that:(1)the expression level of Met in the migrants was significantly higher than the residents,however,the expression levels of CRY1,CRY2,and JHAMT were not significantly different between migrants and residents.(2)The expression of CRY2 significantly negatively correlated with the expression of Met,and significantly positively correlated with the expression of JHAMT.This result indicated that Met plays an important role in determining the migrants and residents of the rice leaf folder,and CRY2 may relate to the regulation of Met. |
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