| Maize is an important food crop in Guizhou Province,and the Asian corn borer Ostrinia furnacalis is one of the major pests that damage maize,seriously affecting its quality and yield.Heat shock protein is a kind of resistance protein produced by organisms in adapting to the adverse external environment,and plays an important role in the insects’response to external stresses.In this study,the field occurrence pattern of O.furnacalis was clarified by investigating the field growth dynamics and migration pattern of O.furnacalis in Guizhou Province for two consecutive years,which provided a scientific reference basis for the effective formulation of control strategies and timely control measures.Two small molecule heat kinin genes,Hsp24.3and Hsp21.8,were cloned from the O.furnacalis using RT-PCR,and their sequence characteristics and homology were analyzed based on bioinformatics;their expression profiles in different developmental stages and different tissues of the O.furnacalis were detected using real-time fluorescence PCR;the expression profiles of Hsp24.3and the differential expression of Hsp24.3 and Hsp21.8 under different stress factors was investigated to lay the foundation for revealing the molecular mechanism of O.furnacalis in response to environmental stresses.In addition,The main findings of this paper are as follows:1.Investigation on the occurrence pattern of O.furnacalis in Zhijin County（1）Field occurrence pattern of O.furnacalisin Zhijin CountyThe main Lepidoptera pests of maize in Guizhou Province are O.furnacalis,Mythimna separata and Conogethes punctiferalis.O.furnacalislarvae occur throughout the reproductive period in both spring and summer corn fields,with the most occurrence in the male twitching and milk ripening stages of spring corn and the most occurrence in the waxing stage on summer corn.O.furnacaliswas found at much higher rates than several other Lepidoptera pests at all periods of spring and replanted corn.The 2017-2018 survey found that three peak adult moth trapping periods occurred each year,and these peaks occurred in early-mid June,early-mid August,and early September.In terms of eggs and larvae three peak egg drop and three peak larvae occurred,which tentatively suggests that corn borer may occur incompletely three generations a year in the area.Adults of the overwintering generation of Asian corn borer gradually occur in corn fields in normal years in mid to late May,and one generation of eggs are gradually produced in early June,and the damage of Asian corn borer occurs in the field in late June.The first generation of adults appeared in the field in mid-July,the second generation of eggs appeared in the field in late July,and the damage of the second generation of larvae appeared in early August until the ears were picked.（2）Migration pattern of O.furnacalisin the fieldThe number of adult O.furnacalismoths trapped at different distances during the same period did not show a significant trend of decreasing with increasing distance,which indicates that the flying ability of adult O.furnacalismoths is relatively strong and their activities are not limited to the vicinity of the plumage site.The field system survey of O.furnacalis showed that the closer the spring sown corn field was to the village,the larger the number of eggs and larvae of O.furnacalisand the more serious the damage was,and the village was the main source of insects for spring sown corn;after replanted corn was planted,the spring sown corn field became its main source of insects again,and rapidly spread to the surrounding replanted corn fields.It is recommended that in production practice:spring and resown maize should be controlled within 1.0 km from the source of insects as a priority.In this study,the second generation of O.furnacalis nymphs were not found in replanted corn fields at different distances,indicating that two generations of O.urnacalisstill occur mainly in this area in a year.2.Cloning and expression profiling of O.furnacalis heat kinin genes Hsp24.3 and Hsp21.8In this study,we used reverse transcription-polymerase chain reaction（RT-PCR）to clone maize stem borer heat kinin genes Hsp21.8 and Hsp24.3,and analyzed their sequence characteristics by bioinformatics methods.The expression patterns of Hsp21.8 and Hsp24.3 genes in different ages and adults of maize borer were examined by real-time quantitative PCR（RT-q PCR）.The results showed that the open reading frame of Hsp21.8 gene was 588 bp long,encoding 195 amino acids;the relative molecular weight of the encoded protein was 21.83 k D;the isoelectric point（pl）was 6.25;the total number of negatively charged residues（Asp+Glu）was 31 and the total number of positively charged residues（Aro+Lys）was 28;the molecular formula was Hsp24.3 has an open reading frame of 663 bp,encodes 220 amino acids and has a relative molecular weight of 24.33 k D;the isoelectric point（pl）is 4.6;the total number of negatively charged residues（Asp+Glu）is 37 and the total number of positively charged residues（Aro+Lys）is 28.The total number of positively charged residues（Aro+Lys）is 22;the molecular formula is C1095H1691N281O344S2;it has the amino acid profile of cytoplasmic-type heat kin and belongs to cytoplasmic heat kin.The Hsp24.3 and Hsp21.8 genes were expressed throughout the developmental stages of the corn borer,with the relative expression of the Hsp21.8 gene being the highest in the pupal stage,4.02 times higher than that of the adult females and 26.13times higher than that of the males,with a slight fluctuation in relative expression from the egg stage to the 5th instar;the relative expression of the Hsp24.3 gene was the highest in the males,8.98 times higher than that of the females The relative expression of Hsp24.3 gene was 8.98 times higher in males than in females,and the relative expression fluctuated slightly from egg stage to pupal stage.Overall,the relative expression of Hsp24.3 and Hsp21.8 genes was relatively stable before the pupal stage of O.furnacalis.3.Expression of Hsp24.3 and Hsp21.8 in response to environmental stress in O.furnacalisThe differential expression of Hsp24.3 and Hsp21.8 genes in response to UV-A,high and low temperature stresses was examined.The results showed that under UV-A stress,the relative expression of Hsp21.8 gene peaked at 60 min and 30 min in male and female adult O.furnacalis,respectively;Hsp24.3 peaked at 150 min and 120 min,respectively;under 4℃stress,the relative expression of Hsp24.3 gene peaked at 120min in both male and female adult O.furnacalis.Under 36℃stress,the relative expression of Hsp21.8 gene peaked at 60min in both male and female adult O.furnacalis,and Hsp21.8 gene peaked at 90min in both male and female adult O.furnacalis. |
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