Ultrastructure And Indentification Of The Chorion In Nilaparvata Lugens (St(a|°)l)

Insect eggshell morphogenesis is a gradual process involving intense syntheticand secretory activity of the follicular cell during the late stages of oogenesis. Theeggshell is a highly organized supramolecule and largely proteinaceous structuresfeaturing regional complexity. Studies on insect eggshell show that different orders ofinsects have eggshells of widely different structure, composition and mechanism ofeggshell assembly. The present study was to investigate, by means of light andscanning electron microscopes (TEM, SEM), the morphological details andmechanism of eggshell assembly of chorion of Nilaparvata lugens (St l) and toattempt to separate chorion proteins of N. lugens by SDS-PAGE andMALDI-TOF-MS. The major results are as follow:1. The results showed that the chorion of N. lugens and Sogatella furcifera (Horváth)are smooth. Their operculum and the hatching line were similar, facilitatinghatching of the larva, however, the function of their operculum areas weresignificant different, the former one was help eggs attaching host plant. Besides,one micropyle with a “channel” was observed on the anterior pole of the eggallowing for entrance of the sperm.2. The chorion of N. lugens and S. furcifera consisted of two layers with differentelectron density. The exochorion of them were thin about300nm and250nm, and closely adheres to the endochorion. The endochorion was thinner (900nm and650nm) than exochorion and had a higher electron density. TEM studies ofdifferent stages of N. lugens showed that the formation of its eggshell, like otherinsects, is a gradual process involving intense synthetic and secretory activity ofthe follicular cell.3. This paper attempted to find out the better acrylamide gel concentration and wayof sample preparation in order to optimize the effect of SDS-PAGE. Using15%acrylamide gel concentration to separate chorion of N. lugens. Subsequentelectrophoretical analysis showed that the chorion is of a proteinaceous nature andconsists of2polypeptides with an estimated molecular weight of50-,40-kDa.Further MALDI-TOF-MS analyze showed the two of them as chorion proteins,one is small hot shock protein and the others are vitellogenin.4. The research of different stages of N. lugens egg showed that there were changesof protein composition. During the early stage of this period, the most notablechange was the accumulation of yolk proteins. Also there was a significantreduction of protein variety and the chorion was formed during the last stage.The operculum of N. lugens is help eggs attaching host plant and facilitatinghatching of the larva; their chorion are consist of two layers and may involveintercalation events during eggshell formation; two separated chorion proteins of N.lugens are low molecular protein. These results will help to provide a betterunderstanding of eggshell structure, formation, protein composition and basicinformation to research of insecticide.