| Spodoptera frugiperda,a crop pest that continues to migratory around the world.It has spread rapidly to other parts of China since its discovery in Yunnan in 2018,seriously harming the country’s crop economy.In recent years,due to the increase of pest resistance induced by chemical pesticide and environmental pollution,physical prevention and control is increasingly concerned.LED light,as a new environmentally friendly light source,not only has obvious effects on moth pests but can also avoid negative effects on crops.Vitellogenin receptor regulates endocytosis mainly by binding with vitellogenin,and plays a decisive role in vitellogenin deposition,ovarian development and reproduction of insects.In this thesis,S.frugiperda was used as an experiment object,the full-length sequence of the vitellogenin receptor gene of S.frugiperda(Sf Vg R)was amplified for the first time and analyzed its sequence characteristics and expression pattern.The effects of LED light on growth,development,and reproduction of S.frugiperda were studied,and the m RNA expression levels of Sf Vg and Sf Vg R were analyzed in S.frugiperda after LED light treatment with different wavelengths.The effects of ds Sf Vg and ds Sf Vg R on vitellogenin and its receptor genes in S.frugiperda were investigated using RNAi technology.The main conclusions were as follows:1.Effects of 520 nm and 570 nm LED light on growth,development,and reproduction of S.frugiperdaDifferent LED light had important effects on the growth and development of S.frugiperda.The results showed that the entire generation of S.frugiperda was significantly shortened under 520 nm treatment compared with the control(P<0.05).The pupation rate and eclosion rate were significantly decreased,only 41.44%(P<0.01)and 71.75%(P<0.05)of control,respectively.The fecundity was only 17.54%(P<0.001)of control,and the preoviposition period was significantly extended(P<0.05).Under 570 nm treatment,the egg stage and larval stage were significantly shortened,and the pupation rate and eclosion rate were significantly decreased(P<0.05),while there was no significant difference in fecundity and the preoviposition period(P>0.05).The results showed that the two kinds of LED light had inhibitory effects on the growth and development of S.frugiperda,and 520 nm LED green light significantly inhibited the reproduction of S.frugiperda.2.Analysis of the characteristics of the Sf Vg RThe full-length of Sf Vg R was amplified for the first time.The full length was5,629 bp,contains a 5,280 bp open reading frame,as well as the 5’ non-coding region of 170 bp and the 3’ non-coding region of 179 bp,encoding a polypeptide composed of 1,759 amino acids.The molecular weight of Sf Vg R was 197.71 k Da with a proposed isoelectric point of 5.02.Sf Vg R belong to the low-density lipoprotein receptor(LDLR)family,which includes five conserved domains.Phylogenetic analysis showed that the Sf Vg R were closely related to other lepidoptera and were clustered together,indicating that vitellogenin receptors were highly conserved in evolutionary terms and were consistent with the traditional evolutionary relationship.3.Effects of 520 nm and 570 nm LED light on Sf Vg and Sf Vg RReal-time quantitative PCR was used to analyze the Sf Vg R m RNA expression level of S.frugiperda in different developmental stages and tissues.The results showed that Sf Vg R gene was expressed only in female pupae and female adults and reached its peak on the third day after emergence.In addition,the Sf Vg R gene was also specifically expressed only in the ovary in different tissue.The m RNA expression levels of Sf Vg and Sf Vg R genes of S.frugiperda were also detected after two kinds of LED light treatment.The results showed that the m RNA expression levels of Sf Vg and Sf Vg R genes in female adults were significantly inhibited under520 nm LED light treatment.The levels of expression decreased by 33.90% and49.25%,respectively(P<0.05).Under 570 nm LED light treatment,the expression levels of two genes were not significantly different from those of the control.This is consistent with the effect of the treatment on the fecundity of S.frugiperda.The results showed that 520 nm LED green light inhibited the expression of Sf Vg and Sf Vg R genes in S.frugiperda,thereby reducing the fecundity.4.The function of Sf Vg and Sf Vg R was verified by RNAiThe function of Sf Vg and Sf Vg R in S.frugiperda were studied after microinjection of ds RNA.The results showed that compared with the control group,the m RNA expression levels of target genes in female adults were decreased by 83.05%and 79.78% after injection of ds Sf Vg and ds Sf Vg R,respectively(P<0.0001).But neither affected the expression of the other gene.This suggests that the decreased Vg levels in the ovary are due to a lack of Vg R-mediated Vg uptake into oocytes,rather than a decrease in Vg synthesis.In addition,to investigate the reproduction and development of ovaries in female adults of S.frugiperda after injection of ds Sf Vg and ds Sf Vg R,it was found that the reproduction in the two treatment groups decreased significantly,only 29.68% and39.98% of the control group.In addition,the ovarian development of the two treatment groups was obviously immature,the volume of follicles decreased,and the content of yolk deposition in oocytes was also significantly reduced.These results suggest that RNAi-mediated knockdown of Vg and Vg R gene may play a key role in regulating the reproductive ability of S.frugiperda.In conclusion,appropriate wavelength LED lighting can inhibit the growth and reproduction of S.frugiperda.Significant differences in reproduction and ovary development revealed the importance of Sf Vg and Sf Vg R gene silencing in inhibiting their reproduction,which provided evidence that the two genes play a key role as targets in regulating the population growth of S.frugiperda,and provided theoretical basis and practical guidance for the successful implementation of integrated pest management(IPM)measures. |
