Function Of Chloroplast Glyceraldehyde-3-phosphate Dehydrogense In The De Novo Synthesis Of Fatty Acids In Arabidopsis Seed

Chloroplast glyceraldehyde-3-phosphate dehydrogenase is the keyenzyme that catalyze the Calvin cycle to promoting CO2 fixation, main specific bind of NADPH tocatalytic reduction of 1,3-diphosphoglycerate to glyceraldehyde 3-phosphate. Chloroplast GAPDHconsist oftwo subunits :GAPA and GAPB, GAPA are divided into GAPA1 and GAPA2. In plantsde novo synthesis of fatty acids occurs in plastids,additionevery two carbon to acyl chain in fatty acid synthesis requirethe proportion ATP, acetyl-coenzyme A, NADPH. The photosynthetic type seeds due to the presence of photosynthetic pigments that can use solar energy to generate ATP and NADPH.However, these experiments were in vitro or shading conditions and did not provide the genetic evidence. Thus, the present study was to determine the underlying decision came photosynthetic type seed fatty acid de novo synthesis of reducing power source through the use of chlorophyll biosynthesis in Arabidopsis mutants, as well as the absence of chlorophyll biosynthesis of chlorophyll seed expression microarray analysis and other methods,and its main results are as follows: 1. we found that in the absence of chlorophyll, the grain weight of seeds were able to meet 90% of wild-type seed,oil accumulation may reach 85% of wild-type, chloroplast GAPDH was upregulatedduring the process. This shows that photosynthesis reducing power generated within the photosynthetic type seeds may not be the main source of de novo synthesis of fatty acids in reducing power. 2.Inexpression microarray analysis we found in no chloroplasts of Arabidopsis seeds chloroplast glyceraldehyde 3-phosphate dehydrogenase(GAPDH) was upregulated, indicating chloroplast glyceraldehyde 3-phosphate dehydrogenase in the de novo synthesis of fatty acids may play an important role. 3.To understand the function of chloroplast GAPDH in the de novo synthesis of fatty acids, we constructed a series of GAPA, GAPB overexpression and antisense transgenic lines. Surprisingly, the overexpression transgenic lines have decreased oil content of 2%-4%, but antisense transgenic lines increased oil content of 2%-4%.In this study, this results indicate that GAPA, GAPB may not provide reducing power to de novo fatty acid synthesis process. 4.We found the chloroplast GAPDH expression in peanuts during the developm ent is low, but high in the expression of cytoplasm GAPDH- GAPC. GAPC m ajor catalyzeglyceraldehyde 3-phosphate into 1,3-diphosphoglycerate in glycolysis.Glycolysis can produce large amounts of carbon metabolites, ATP and reducing power, these substances are required for the synthesis of fatty acids. Therefore,GAPC may play an important role in fatty acid synthesis.