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Open Access Research article

Genome-wide regulation of innate immunity by juvenile hormone and 20-hydroxyecdysone in the Bombyx fat body

Ling Tian1, Enen Guo2, Yupu Diao1, Shun Zhou1, Qin Peng1, Yang Cao2, Erjun Ling1 and Sheng Li1*

Author Affiliations

1 Key Laboratory of Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China

2 Department of Sericulture Science, College of Animal Sciences, South China Agricultural University, Guangzhou 510642, China

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BMC Genomics 2010, 11:549  doi:10.1186/1471-2164-11-549

Published: 9 October 2010

Abstract

Background

Insect innate immunity can be affected by juvenile hormone (JH) and 20-hydroxyecdysone (20E), but how innate immunity is developmentally regulated by these two hormones in insects has not yet been elucidated. In the silkworm, Bombyx mori, JH and 20E levels are high during the final larval molt (4 M) but absent during the feeding stage of 5th instar (5 F), while JH level is low and 20E level is high during the prepupal stage (PP). Fat body produces humoral response molecules and hence is considered as the major organ involved in innate immunity.

Results

A genome-wide microarray analysis of Bombyx fat body isolated from 4 M, 5 F and PP uncovered a large number of differentially-expressed genes. Most notably, 6 antimicrobial peptide (AMP) genes were up-regulated at 4 M versus PP suggesting that Bombyx innate immunity is developmentally regulated by the two hormones. First, JH treatment dramatically increased AMP mRNA levels and activities. Furthermore, 20E treatment exhibited inhibitory effects on AMP mRNA levels and activities, and RNA interference of the 20E receptor EcR-USP had the opposite effects to 20E treatment.

Conclusion

Taken together, we demonstrate that JH acts as an immune-activator while 20E inhibits innate immunity in the fat body during Bombyx postembryonic development.