VITELLIN OF THE SWEET-POTATO WHITEFLY, BEMISIA-TABACI - BIOCHEMICAL-CHARACTERIZATION AND TITER CHANGES IN THE ADULT

SDS-PACE of the sweet potato whitefly (Bemisia tabaci) egg extract sho wed one major band (approximately 190 kDa) and two minor bands (approx imately 75 kDa and 67 kDa). A distinct 190 kDa band was also present i n male extract. On SDS gels the vitellin band of the greenhouse whitef ly (Trialeurodes vaporarium) was larger, about 220 kDa. The native mol ecular mass of sweet potato whitefly vitellin was estimated to be 375 kDa using 4-20% native pore-limiting gel electrophoresis. Its isoelect ric point was estimated to be 7.3 using isoelectric focusing. Two-dime nsional gel electrophoresis and densitometry were used to estimate vit ellin subunit composition; the data suggest that the sweet potato whit efly vitellin is likely to be a 380 kDa native molecule formed by two 190 kDa subunits. The two minor bands (75 kDa and 67 kDa) may be break down products of the native vitellin. This conclusion was supported by a Western blot of an SDS-PAGE gel of partially degraded female and eg g extracts, which showed that polyclonal antiserum raised against the 190 kDa polypeptide recognized the 75 kDa and 67 kDa bands. Seven hybr idoma cell lines secreting monoclonal antibodies against the 190 kDa b and were screened, and one of them (S1A2G9H2) was mass produced. The a ntibody recognized the 190 kDa band in a Western blot. All the screene d monoclonal antibodies were female and egg-specific by ELISA and/or W estern blot, suggesting that the 190 kDa band in male extract was not a vitellin. A sensitive ELISA was established that could detect as lit tle as 1/40 of an egg equivalent of vitellin using the monoclonal anti body from S1A2G9H2. Profiles of female sweet potato whitefly reproduct ive activities (egg laying, amount of vitellin in the female, and tota l vitellin produced by a female) within 2 days after eclosion were det ermined. (C) 1997 Wiley-Liss, Inc.