The Phenotype of a Virescent Chloroplast Mutation in Tobacco Is Associated with the Absence of a 37.5 kD Thylakoid Polypeptide

Abstract

The Vir-c mutation is a virescent chloroplast mutation found in a line of plants derived from protoplast fusions between a Nicotina tabacum line and a line containing N. tabacum nuclei with Nicotiana suaveoeas cytoplasm. Vir-c displays a lag period in chlorophyll accumulation and granal stack formation in young leaves. We examined total chloroplast protein in young leaves and showed the mutant contains 1.3 to 2.1 times less stromal protein, and 2.9 to 4.3 times less thylakoid protein when compared to the N. tabacum var "Turkish Samsun" control. Electrophoretic patterns of total thylakoid proteins indicated three polypeptides were specifically decreased in amount within the context of the overall reduction in thylakoid protein. Electrophoresis of thylakoid proteins synthesized by chloroplasts isolated from half-expanded leaves demonstrated that mutant chloroplasts did not synthesize a 37.5 kilodalton polypeptide which was synthesized by "Samsun" chloroplasts. A polypeptide of this molecular weight was synthesized by Vir-c chloroplasts isolated from mature leaves which had recovered the normal phenotype. Restriction

Envelope K+/H+ Antiporters AtKEA1 and AtKEA2 Function in Plastid Development

“…Recovery of pigmentation is typical of virescent mutants, which show defects in photosynthetic pigments in young and emerging tissues but gradually turn green along the leaf proximal-distal axis. This is often related to the altered expression of genes involved in early chloroplast biogenesis, causing delayed chloroplast development (Archer et al, 1987;Lopez-Juez and Pyke, 2005). We suggest that, even though growth is retarded, chloroplasts of kea1kea2 mutants eventually develop to form functioning organelles, resulting in less severe phenotypes in older leaves.…”

A frameshift mutation of the chloroplast matK coding region is associated with chlorophyll deficiency in the Cryptomeria japonica virescent mutant Wogon-Sugi

“…In higher plants, chlorophyll-deficient mutants such as albino, variegated and virescent mutants have been selected and utilized to elucidate the development and function of the chloroplast. The virescent forms of these mutants are phenotypically characterized as having a lag in chlorophyll accumulation in young leaves (Archer and Bonnett 1987 ; Archer et al 1987 ) and have been isolated in a wide range of flowering plants including rice (Iba et al 1991 ), barley (Jain 1966 ), maize (Hopkins and Elfman 1984 ), cotton (Benedict and Kohel 1970 ), tobacco (Archer and Bonnett 1987 ; Archer et al 1987 ), and peanut (Benedict and Ketring 1972 ).…”

Protein synthesis by isolated chloroplasts

“…Archer et al (1987) have used the system to diagnose the molecular basis of a chloroplast coded virescent mutant in tobacco. From their experiments on in organello protein synthesis, they concluded that the inability of plastids from the mutant to make a 37.5 kDa polypeptide was probably the causal factor of this mutation and thus this polypeptide might be important for the assembly of pigment-protein complexes in the developing world.…”