DO LIGHT-INDUCED PH CHANGES WITHIN THE CHLOROPLAST DRIVE TURNIP YELLOW MOSAIC-VIRUS ASSEMBLY

Turnip yellow mosaic virus (TYMV) induces gross morphological and bioc hemical changes in the chloroplasts of infected cells. Viral RNA is sy nthesized in vesicles formed by invagination of the outer chloroplast bilayer. Virion assembly occurs at the neck of these vesicles and requ ires illumination. Data collected over the last three decades are cons istent with the hypothesis that light-induced generation of a low pH d rives TYMV assembly within the intermembrane space of chloroplasts. In a low-pH environment, poly(C) regions within the genomic RNA of TYMV may interact to form tertiary structures, and the recognition of these structures by TYMV coat protein initiates virion assembly.