Regulation of chloroplast gene expression is affected in ali, a novel tobacco albino mutant

An albino mutant designated all was isolated from an M-2 population derived from a tobacco (Nicotiana tabacum L. 'BY-4') plant which had been irradiat ed with a N-14-ion beam at an early stage of embryonic development. Leaf me sophyll cells of ali were devoid of developed chloroplasts, and no stacked thylakoid membranes could be detected in the plastids. The reduction of pig ment and the arrest of chloroplast development in all were associated with distinct alterations in gene expression. Expression of plastid-encoded gene s for the photosynthesis system (rbcL, psbA) was greatly reduced in ali, bu t at the transcript level plastid-encoded genes for 23S rDNA and 16S rDNA e xpression were only slightly reduced. Transcription of the nuclear-encoded Lhc and rbcS genes in the mutant was similar to that in the wild-type, Ther e was no accumulation of Rubisco-L, Rubisco-S, and PSII-DI polypeptides in the ali mutant. The number of chloroplasts per cell was similar in both ali and wild-type plants. These results suggest that ali is a novel albino mut ant in which chloroplast gene expression is affected. (C) 2001 Annals of Bo tany Company.