Studies On The Metabolic Adaptation And Transcriptomics Mechanism Of Lipid Metabolism In Diapause Coccinella Septempunctata L.

With the development of technology and utilization of pest Green prevention and control of crops, the merit of Biological Control is increasingly important. Coccinella septempunctata L., praying on aphids, coccid etc., is an agent of natural enemies, which has been commercialized and utilized extensively in countries. Diapause is an inherit attribute of many natural enemies, and regulation natural enemy diapause could extend shelf-life, assure long-distance shipment and improve stress resistance of natural enemy, promoting storage, shipment and massive usage of this special goods. Diapause studies of C. septempunctata, including diapause anatomy features, artificial regulation, post-diapause traits, diapause mechanism, improve acquiring diapause traits of C. septempunctata further, and provide guidance to production practices.Storage and utilization of nutrients during diapause are crucial for insects passing diapause successfully. Based on anatomy of diapause ladybeetle, we systematically detected water content, lipid, carbohydrate and protein content of normal development(ND), diapause(D) and post-diapause(PD) insects. Then, super-cooling point(SCP) was measured within above three different developmental stages. Furtherly, we did RNA-seq by transcriptome for ND, D and PD ladybeetle, acquiring massive differential expression Unigenes. Based on transcriptical profiles, we selected genes associated with lipid metabolism and analised deeply surving as a reference on nutrients’ utilization and regulation for diapause ladybeetles. Main results are as follows:1. Primary biochemical substances among ND, D and PD showed significant difference, including water content, lipid, carbohydrate and total protein. Water content and total protein were lowest in diapause ladybeetles compared with normal development and post-diapause individuals’, indicating that metabolism in diapause was depressed. Lipid, sugars and glycogen were important nutrient of diapause ladybeetle: lipid in diapause ladybeetles’(173.66±19.01 μg/mg) was twice more than ND(80.04±15.82 μg/mg) and PD(83.83±12.54 μg /mg); total sugar and glycogen were twice and seven times more than ND and PD. However, glycerol, sorbitol and trehalose showed no difference among ND, D and PD individuals. Besides, diapause ladybeetle accumulated a great deal of glycogen rather than trehalose, and trehalose showed no significant different among ND, D and PD ladybird, confirming that C. septempunctata belongs to glycogen accumulation.2. Cold hardiness of diapause C. septempunctata was elevated. The SCP of diapause ladybeetle was-16.53 ℃, but lower than normal development individuals’(-14.07 ℃) and post-diapause individuals’(-15.29 ℃). After diapause acclimation, cold hardiness of post-diapause increased.3. We used transcriptional technology checked ND, D, and PD transcriptional profiles. Via splicing, filtering and stitching, we obtained 82,820 Unigenes with 3,501 Unigenes were differentially expressed between D-ND, including 2,125 upregulated Unigenes in diapause and 1,376 downregulated Unigenes; after comparison between PD and D, we acquired 1,427 Unigenes with 749 upregulated Unigenes in diapause and 678 downregulated Unigenes. These differentially expressed Unigenes enrichment mainly distributed in molecular function category, fatty acid metabolism pathway, drug metabolism, and carbon metabolism etc. pathwaies.4. By comparison of D-ND and PD-D differential expressed genes and KEGG database, 17 Unigenes with lipid metabolism function were selected, involving in fatty acid synthesis, β-oxidition, transport etc., showing differential expression during diapause. Fatty acid synthase, elongation of fatty acid protein, lipid transport protein etc. were upregulated in diapause individuals, and some lipid degradation proteins also upregulated in diapause ladybirds, such as esterase, acyl-CoA acetyltransferase, related to raise diapause ladybirds’ immunity perhaps. Besides, some proteins correlated with hormone synthesis were upregulated, related to depressed ovary development of diapause C. septempunctata perhaps.