INHIBITION OF INCREASE AND ACTIVITY OF TOBACCO-MOSAIC VIRUS UNDER NITROGEN-DEFICIENT CONDITIONS

Abstract

Expts. were carried out to determine in what way tobacco-mosaic virus (Mar-mor tabaci) is affected in Turkish tobacco plants (Nicotiana tabacum) deficient in N. Representative diseased N-fed and N-deficient plants were harvested at 4-day intervals and the expressed juice assayed for relative virus activity, total protein and virus protein. In N-deficient plants the virus-protein content as well as the content of soluble plant protein remained practically constant, whereas in N-fed plants each increased more than 5 times during a 16-day period. However, although no decrease in the yield of virus protein in the N-deficient plants could be detected, its biol. activity decreased more than 40%. It is not known how this inactivation was brought about. As far as the N-deficient plant is concerned, the virus protein acts as a foreign protein, for the virus was apparently not affected by the normal proteolytic processes of the plant. Even a plant suffering from a severe N-deficiency was unable to use, in the synthesis of its normal proteins, any N previously utilized by the virus; the virus was unable to utilize any N tied up in the proteins normally present in a N-deficient plant, for in the absence of an external supply of N, no further virus multiplication could be detected.