Abstract
Plastid-derived signal, "plastid signal", plays an important role for the coordinated expression of nuclear genes encoding for photosynthesis-related proteins with the functional status of chloroplast. Arabidopsis GUN loci have been identified as primary component of plastid signaling. gun mutants have Lhcb expression in the absence of proper chloroplast development, while it is strongly repressed in wild type. There are at least two types of the signal pathways, tetrapyrrole-dependent and tetrapyrrole-independent pathway. At present, seven "tetrapyrrole pathway" mutants are identified including gun2-gun5. gun1 is the sole "non-tetrapyrrole pathway" mutant to date. In the tetrapyrrole pathway, Mg-protoporphyrin IX and its methyl ester are proposed to be the signal(s), which reflect the functional status of plastids. The phenotype of newly identified tetrapyrrole pathway mutants will be reported. We will also present the data of T-DNA insertion mutants of PARPs (ZAP & NAP; candidate genes of GUN1).
