Comparison of expression of the genes associated with immunity and development between Apis cerana cerana and Apis mellifera ligustica infected with sacbrood virus

Abstract:

[Objective] To investigate the effects of sacbrood virus (SBV) infection on the genes associated with the immunity, metabolism, resistance to virus, and cell growth and metabolism of Apis cerana cerana and Apis mellifera ligustica. [Methods] The 2-day-old larvae were collected from the colonies of A. c. cerana and A. m. ligustica and reared in an incubator at 34 ℃ and RH 85%. The larvae were infected with SBV at 3 days old, and the dead larvae were then recorded every day. Real-time quantitative polymerase chain reaction (RT-qPCR) was employed to measure the expression levels of gene SBV, as well as the genes associated with immunity (Apidaecin, Abaecin, Hymenoptaecin, Defensin, Lys-1, Pgrp-lc, Kenny, and Domeless), metabolism (Ilp1, Hex110, and Vg), resistance to viruses (Dis3, Dicer, and Ago1), and cell development and metabolism (Vhdl, Co-1-iv, and Mta1), in the 4- and 7-day-old larvae. [Results] After infection with SBV at the same dose, all the larvae of A. c. cerana died at 8 days old, while some larvae of A. m. ligustica emerged. The relative expression of SBV in A. c. cerana was significantly higher than that in A. m. ligustica of the same days old. Compared with the control group, SBV infection significantly up-regulated the expression of Abaecin, Apidaecin, Hex110, Dicer, and Vhdl in the 4-day old larvae of A. c. cerana, and it up-regulated the expression of Hymenoptaecin and Ago1 and down-regulated that of Apidaecin, Abaecin, Vg, and Vhdl in the 4-day-old larvae of A. m. ligustica. In addition, SBV infection down-regulated the expression levels of Hex110, Dis3, and Ago1 in the 7-day-old larvae of A. c. cerana and Ilp1, Dicer, and Co-1-iv in the 7-day-old larvae of A. m. ligustica. [Conclusion] The larvae of A. c. cerana were more susceptible to SBV infection than those of A. m. ligustica. The significant differences in the expression levels of the genes involved in immunity and development between A. c. cerana and A. m. ligustica may be associated with the differences in the defense mechanism against diseases and pests, the regulation of nutrient metabolism, and the virus-caused siRNA response.