Study of compensatory growth based on different nutrition conditions of Bombyx mori

Abstract

• Various body weight gain rates of Bombyx mori occur in response to variable food regimes. • Compensatory growth in Bombyx mori partially prevents body weight loss. • Compensatory growth affects digestive enzyme activities. • Digital gene expression profiling was used to analysis of differentially expressed genes. • Compensatory growth affects the gene expression levels of PI3K/AKT signaling pathway. Organisms achieve compensatory growth after a period of nutrient restriction followed by recovering the nutrient status . However, the underlying mechanisms associated with such growth acceleration remain unclear. The silkworm Bombyx mori is a lepidopteran model insect. This study aimed to investigate the physiological characteristics and the underlying mechanisms in B . mori fed on mulberry leaves (MG), artificial diet (AG), and artificial diet + mulberry leaves (AG-MG), respectively. Silkworms in AG-MG which fed on artificial diet from 1st to 3rd instars followed by feeding on mulberry leaves from 4th to 5th instars exhibited a higher weight gain rate than that in MG and AG, indicating that compensatory growth occurred as a result of the switch in the silkworm food regime. Trypsin and lipase activities of silkworms in AG-MG were shown to be up-regulated at 72 h after changing food. Digital gene expression profiling (DGE) analysis revealed that genes related to metabolism and development in silkworm midguts were differentially expressed. The quantitative real-time PCR (qRT-PCR) results showed that the expression levels of IIS/PI3K-AKT pathway genes including INR , IRS , AKT , PI3K60 and PI3K110 of silkworms in AG were down-regulated compared with that in MG at 0 h. Whereas AKT, PI3K and PI3K60 of silkworms were significantly increased by 1.68-, 1.49-, 1.67-fold, respectively, at 72 h after switched to mulberry leaves than the same instar fed on artificial diet. PDK ’s expression of silkworms in AG was higher than that in other two groups at each timepoint. Compared with MG and AG, PTEN and IRS were down-regulated at 48 and 72 h in AG-MG. Collectively, these results indicate that compensatory growth in B . mori is regulated by IIS/PI3K-AKT signaling pathway.