Proteomics Analysis Of Larval Midgut From The Silkworm, Bombyx Mori

The silkworm, Bombyx mori, is herbivorous insect. It is a lab-reared animal and its relatively large size make silkworm as a model organism for Lepidoptera pest. The genomic project of Bombyx mori was completed in 2004, combined with EST sequence, we construct the hypothetical protein database of silkworm, which provide us a database for proteomics research.The silkworm, as a holometabolous insect, has four remarkably different developmental stages: egg, larva, pupa, and moth. The larva is the only stage in the whole silkworm life cycle that feeds. This stage, especially the 5th instar larvae accumulate most nutrition, is very important for growth, development, and silk production. The midgut is the major organ for food digestion, nutrient absorption and also a barrier for foreign substance which serve as a target for insect control.Starvation affects insects on many aspects including behavior, development, life span, reproduction and metabolism. As one of the important tissues responsible for food digestion and nutrition absorption, larval midgut is also a target tissue to study the responses to starvation. Hence, the proteomic research of larval midgut in silkworm is very important for us to understand the mechanism of food digestion and the stress mechanism under this disadvantage condition.In this study, we used 2-DE and matrix assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) to analyze the midgut proteins from the 5th instar larvae as well as the midgut proteins under starvation conditions. The main results we abtained are as follows:1. A total of 96 proteins were identified in this study and among them,69 proteins were observed in silkworm midgut for the first time.2. The numbers of protein spots were gradually increased along with the growth of larvae, especially those ranging in size from 30 kDa to 90 kDa at higher pl region.3. We found the silkworm larval midgut responded to starvation by producing a 10 kDa heat shock protein and a diapause hormone precursor to increase the survival rate under disadvantage condition.