| Frankliniella occidentalis is a widespread and highly adaptable horticultural pest that has now spread to many countries and poses a serious threat to agricultural production.F.occidentalis are highly adaptable and can grow,develop and reproduce on a wide variety of plants in different habitats,and cause serious harm.In order to study the relationship between temperature and humidity on population development of F.occidentalis and environmental adaptability,this study conducted high temperature,low temperature and humidity treatment on F.occidentalis reared at constant temperature for a long time under laboratory conditions,and compared with the relevant data of several years ago on CABI.Two small heat shock protein gene fragments were obtained from the transcriptome of F.occidentalis after temperature stress and their expression patterns were analyzed.At the same time,after interfering the expression of two small heat shock proteins in F.occidentalis by RNAi,the survival rate,temperature tolerance and humidity tolerance of F.occidentalis were statistically analyzed,and the interference efficiency of corresponding genes was quantitatively detected.The main research results are as follows:1.Through statistical analysis of different sexes and developmental stages of F.occidentalis exposed to different high/low temperatures for 1 h.The results showed that all of F.occidentalis of developmental stages and sexes died in the range of-15℃-16℃ and 42℃,indicating that the high temperature threshold for F.occidentalis survival was about 41 ℃～42 ℃,and the low temperature threshold was about-15℃～-16 ℃.The high temperature results were similar to the previous data(41 ℃).However,the lower limit of low temperature is 1～2 ℃ larger than-14℃calculated by previous research.Humidity-related research results showed that F.occidentalis had a certain ability to resist drought and adapt to,or even prefer,the high humidity climate.The survival rate of adult thrips was 75%after 48 h in a high humidity environment with RH=100%.In addition,pupae showed stronger drought resistance than adults.About 20%of individuals survived and emerged successfully after 48 h of exposure to extreme drought conditions at RH=0%.2.Two full-length sequences of small heat shock protein genes were cloned based on the transcriptome of F.occidentalis after temperature stress,which were named FoHSP11.6 and FoHSP28.0,and GenBank entry numbers were OK310493 and OK310494,respectively.The full length of the two sequences was 806 and 1,041 bp,and the open reading frame(ORF)was 330 and 768 bp,respectively,encoding 110 and 256 amino acids.Multiple sequence alignment analysis showed that FoHSP11.6 and FoHSP28.0 had high similarity with sHSP of other insects.The phylogenetic tree analysis showed that the two FoHSPs were divided into two different clades,and FoHSP28.0 is clustered with Thrips palmi of Thysanoptera.By comparing the genome sequence and cDNA sequence,it was found that neither of the two contained introns.3.Based on the full-length sequences of two small heat shock proteins of F.occidentalis,the expression patterns of two FoHSPs under different temperatures,exposure times,humidities,developmental stages and sexes were studied and analyzed by real-time fluorescence quantitative detection method.The results showed that FoHSP11.6 was induced by extreme high and low temperature stress in both adults and pupae,while FoHSP28.0 was induced by temperature stress in both adults and second instar nymphs.The expression patterns of FoHSP11.6 and FoHSP28.0 were different in response to temperature stress.FoHSP11.6 was strongly induced under extreme temperature stress,while FoHSP28.0 was overexpressed under relatively mild temperature stress.The temporal expression patterns of FoHSP11.6 and FoHSP28.0 were similar,with the expression levels reaching the peak after 0.5/1 h treatment and then decreasing.The expression levels of FoHSP11.6 and FoHSP28.0 in pupae increased when the relative humidity was low(0-25%)and decreased when the humidity was close to the optimal growth level.The expression level of FoHSP11.6 was higher in adults,and the expression level of FoHSP28.0 was higher in pupae and adults.In addition,we also found that the expression of FoHSP11.6 and FoHSP28.0 in male adults was significantly higher than that in female adults.4.dsRNA was introduced by feeding method,and adult thrips were selected as experimental materials for RNAi to study the effects of interference with FoHSPs in this study on the survival rate,temperature tolerance and humidity tolerance of F.occidentalis,and the interference efficiency of corresponding genes was quantitatively detected.The efficiency detection results of FoHSP11.6 and FoHSP28.0 show that the silencing efficiency in this study can reach 40%～60%.After ingestion of a sucrose solution containing the target gene dsRNA,the survival rate of F.occidentalis adult decreased significantly compared to the control.Compared with dsGFP and CK,the survival rate of F.occidentalis ingesting dsFoHSP11.6 and dsFoHSP28.0 decreased after high and low temperature stress.However,the silenced expression of FoHSPs had little effect on the drought tolerance of F.occidentalis under different humidity.This study clarified the upper and lower limits of temperature that F.occidentalis can tolerate at present,improved the basic data of the influence of humidity factors on F.occidentalis,explored the expression mode of small molecular weight heat shock protein genes in response to temperature and humidity stress,and constructed the RNA interference system of F.occidentalis for analyzing the function of two small molecular weight heat shock protein genes involved in the study.The above research results provided basic data of F.occidentalis for the establishment of ecological adaptation database,the study of population outbreak mechanism and the prediction of potential suitable areas. |
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