Correlation of Plastid DNA Copy Number with Plastid Gene Expression in Various Organs in Mature Pea Plants (Pisum sativum L.)

The correlation of plastid DNA copy number with the organ-specific expression of the plastid gene in mature pea plants was examined. The plastid DNA copy number and several transcript levels were measured by hybridization, and their relative values were compared, with total DNA as an internal standard. Variations in the relative transcript levels of the photosynthesis genes rbc L, psa B, and psb A in different organs were similar to the variations in gene dosage, but those of the ribosomal protein L2 gene were not. The results suggest that gene dosage affects the organ-specific expression of photosynthesis genes. Northern blot analysis showed that the relative amounts of processed transcripts differed in different organs. This implies that the organ-specific stabilization of mRNA also is important for plastid gene expression.