Preliminary Function Analysis Of MTERF Protein PDE191 In Arabidopsis Thaliana

As the physiological characteristics of green plants, photosynthesis is the major energy source for organisms on earth to survive and develop. Chloroplast is important for plant photosynthesis, and chlorophyll plays a crucial role, which absorb light energy, and drive the thylakoid membrane electron to transport. As a result, chlorophyll deficiency often leads to albino phenotype and seedling lethality. Thus we pay more attention on chloroplast biogenesis and the maintenance of chloroplast function. As a very obvious trait mutation, pigment defective mutant is the ideal material to carry out research on structure, function and regulation mechanism of photosynthesis system.The mitochondrial transcription termination factor (mTERF) proteins are important regulators in the transcription of mitochondrial genes. They are encoded by nuclear genes and combine with mitochondrial DNA to terminate the transcription. In recent years, as well as the in-depth study on the transcription of mitochondrial gene and human mitochondrial diseases, people begin to pay close attention to human mTERF. But researches in Arabidopsis is still relatively fewer. Currently, the structure of mTERF family proteins have been slowly explored, but the function and mechanism is needed to be further studied.In this study, we report the characterization of a pigment defective 191(pdel91) in Arabidopsis, which displays an albino phenotype and was seedling lethal. When supplemented with sucrose, it exhibited a delayed greening phenotype. Genetic analysis indicated that the mutant phenotype was a single recessive locus and the genomic complementary experiment further confirmed that the albino phenotype was due to the knockout of the PDE191. We examined the ultrastructure of chloroplasts by transmission electron microscopy (TEM), and investigated that the chloroplasts were smaller and they contained only a few short appressed internal membranes. The PDE191 gene, which is highly expressed in leaves, encodes about 333 amino acids with seven mTERF domains. Sequence alignment revealed that the pTAC7 homologous existed in various plants. Investigation of chloroplast gene expression pattern in pde191-1 mutants, indicated that the levels of nucleus-encoded polymerase-dependent chloroplast genes were increased dramatically, whereas those of plastid-encoded polymerase-dependent chloroplast genes reduced in the mutant. So we implied that PDE191 may regulated the PEP-dependent gene expression as a possible functional component.