Are there chloroplast master controllers?
The radically different phenotype of plastids in photosynthetic compared with non-photosynthetic tissues could most easily be explained if mechanisms existed that simultaneously controlled a large number of genes encoding chloroplast proteins. Arguably, however, plastids play central roles, other than in photosynthesis, in the biology of specific cell types. A biologically economical way of building such plastids would be to have co-ordinated control of genes encoding plastid proteins, irrespective of whether they are directly related to photosynthesis. In other words, the existence of both chloroplast-specific and plastid-generic master switches could be anticipated. Evidence has emerged that is consistent with the existence of both kinds of centralized regulation of gene expression. A common phenotype of the Arabidopsis det1 and the tomato hp-2 mutants is the partial development of chloroplasts in cells or under conditions where they would not normally appear. This includes semi-deve
