Preliminary Investigation Of The Coordination Between Plastid And Nucleus In Arabidopsis

There is an intracellular coordination between nucleus and plastid in the plant cells. Nuclear gene products control the transcription and translation of plastid genes, but the metabolic or developmental state of the plastid can also influence the expression of nuclear genes encoding plastid proteins. Recent studies have indicated that plastids are able to communicate their functional status to the nucleus by sending a "plastid signal" which derives in the change of the concentration of the plastid factors and that the nucleus responds by making appropriate changes in gene expression. Mg-Protoporphyrin â…¨ (MP) , a tetrapyrrole intermediate in the plastid act as a plastid signal. The plastid-to-nucleus signaling mutants of Arabidopsis have been obtained. These mutants are called "gun", for genome uncoupled. Five GUN loci have been reported, and all the five GUN genes except GUN1 have been already cloned.The coordination between nucleus and plastid is mainly involved in the anterograde pathway that nuclear genes control the development of the plastid. From the studies in the variegated mutants (im, var2, var1 and chm), a kind of mutants deficient in plastid development, we know it is the mutations in nuclear genes that induce these phenotype. The mechanism of variegation in chloroplast has been clearly, but one induced by nuclear genes still puzzled us. The genotype of the cell is all the same, but the status in plastid development appears different. These variegated mutants themselves explained the existence of coordination between nucleus and plastid.In this paper, we have screened three gun mutants using the transgenic plants that contain a fusion of the Rbcs promoter to the Gfp gene (Rbcs::Gfp) when treated with norflurazon and lincomycin which influence plastid development greatly. We haven't discovered new GUN locus, but we find it is a new method that gun mutants are screened under the treatment with lincomycin. A metabolic interaction between GUN genes can be inferred through the observation of the phenotype of double gun mutants. Pharmaceutical experiments showed that the redox state of plastid can alsoinfluence the expression of nuclear genes involved in dedifferentiation and differentiation, and that cGMP may act in the signaling transduction downstream of MRFurthermore, we have screened four mutants deficient in plastid development in the EMS mutation pools. The affected loci in the variegated mutants Adl-1 and var-a are allelic to CUE1 and IM respectively. But the phenotype of the mutants pag (pale green) and var-b has it's own future distinctively, not reported in publications before. We consider them may be new genes. And now, the working on the two genes cloning is carrying out.