Variations in the Protein Content and Tobacco Mosaic Virus Contamination of an Endomembrane Fraction from Leaves of Nicotiana tabacum L. “Samsun” after Infection with Tobacco Mosaic Virus

Abstract

The protein content of a fraction of smooth cytoplasmic (= SC) membranes, which was isolated from the resuspended 1,000 to 20,000 g pellet of primarily TMV-infected leaves of Nicotiana tabacum L. “Samsun” and harvested at 27% saccharose of a 10 to 50% saccharose gradient, dropped below that of the initial concentration within few days after inoculation with TMV. Thereafter it increased rapidly, with a maximum reached 8 d post infection. In contrast, the content of membrane-bound active virus increased continuously. The time course of this in-vivo-binding of TMV was different in 4 subfractions of SC membranes isolated from the resuspended pellets after centrifugation at 0 to 1,000 g, 1,000 to 7,000 g, 7,000 to 13,000 g, and 13,000 to 19,000 g. In subfraction no. 2, the contamination with TMV was greatest at 5 d after infection. However, 10 d after infection the TMV content of subfraction no. 1 exceeded that of all other subfractions. The protein content of SC membranes of leaves being secondarily infected with TMV also increased considerably, but only in light-green and not in dark-green tissue zones. Compared with the SC membranes from healthy leaves, we observed a strong binding of BSA to membranes from light-green and a weaker binding to membranes from dark-green tissue.