Study On The Mechanism Of Zucchini-mediated Cotton-specialized Aphid Adaptation To Cucumber

During the evolution process,Aphis gossypii Glover differentiated into different host specific types due to different feeding species.The common host specific types of Aphis gossypii mainly include cotton-specialized and cucumber-specialized.The cotton-specialized aphids cannot directly establish populations on cucumbers,but can establish populations on cucumbers after induction by feeding on zucchini.This study used biology,transcriptomics,microbiology and other technical methods to study the biological characteristics of the cotton-specialized aphids（Hap1 type）after being transferred through zucchini hosts,revealing the adaptation of the intermediate host zucchini to cotton aphid hosts molecular mechanism.This study can provide a scientific basis for the comprehensive control of cotton aphid.The main results of the research are as follows:1.It was clarified that the cotton-specialized aphids（Hap1 type）can establish a population on the cucumber host after continuously feeding on zucchini for 5 generations.Cotton-specialized aphids fed on zucchini hosts for 1–10 generations,denoted as T1–T10.By analyzing the life table data of cotton-specialized aphid on cotton,zucchini and cucumber from T1 to T10 generations,it was found that the survival rate of cotton-specialized aphids on the cucumber host on the 10th day gradually increases after being transferred through the zucchini host.After 5 generations of cotton-specialized aphids feeding on zucchini,the net value-added rate R₀>1 and the intrinsic growth rate r_m>0 on cucumber host.It can be seen that the cotton aphid is a growing population,which can be Steady establishment of populations on cucumber host.2.It was clarified that the effect of feeding on the intermediate zucchini host on the transcriptome of the cotton-specialized aphids.By comparing the transcriptome of cotton-specialized aphids feeding on cotton and zucchini in different generations,it was found that the number of different expressed genes between the cotton-specialized aphids feeding on the host of zucchini and feeding on the cotton gradually increased from T5.There were 828 genes between T6 and T7（577 up-regulated and 251down-regulated）.The differentially expressed genes between T7 and T8 were reduced to 9（4up-regulated,5 down-regulated）,14 between T8-T9（9 up-regulated,5 down-regulated）,and 35 between T9-T10（up 7 and down 28）.The results of KEGG enrichment analysis showed that the differential expressed genes related to the energy metabolism pathway were significantly reduced after being transferred from cotton host to zucchini host,indicating that the cotton-specialized aphid reduced energy metabolism in order to better adapt to the new host.Different expressed genes related to nutrient metabolism pathways required for long-term development,such as amino acids,carbohydrates,fats,and vitamins,were significantly up-regulated.The differential expressed genes related to the synthesis-related pathways of steroid hormones and other secondary metabolites were significantly up-regulated,and the differential genes related to the heterogeneous metabolic pathways of cytochrome P450 were significantly up-regulated.3.It was clarified that the feeding on zucchini significantly affects the composition and relative abundance of cotton-specialized aphids symbiotic bacteria.By comparing the microorganisms in cotton-specialized aphids feeding on cotton and zucchini of different generations,it was found that the dominant bacterial genera in the microbial community of the cotton-specialized aphids samples feeding on zucchini were mainly Buchnera,Arsenophnus and Acinetobacter.Compared with the aphids feeding on the cotton host,the relative abundance of Buchnera in the cotton aphid feeding on the zucchini host increased significantly,and the secondary symbiotic bacteria Acinetobacter,Stenotrophomonas,Pseudomonas,Flavobacterium,and Novosphingobium were significantly reduced.