Functional Characterization Of A DnaJ-like Zinc Finger Domain Protein,EDA3,in Arabidopsis Thaliana

Photosynthetic pigments,including chlorophyll a/b and carotenoids,extensively participate in energy absorption,transmission and dissipation.In our study,we found a DnaJ-like protein harboring quadruple repeats of the zinc finger domain CxxCxGxG played a vital role in carotenoid metabolism and other life stages.EDA3(also named PSA2)was reported to encode a thylakoid luminal protein and was found in a complex harboring PsaG to regulate the assembly of PSI.We quantified the pigments to understand why eda3 mutant has yellow speckle on leaves.The contents of chlorophyll a and b droped to 37%to 45%of the wild-type levels.And those of lutein,?-carotene,violaxanthin and neoxanthin droped to 30%-40%.To further elucidate the molecular mechanism underlying the variation in pigment contents,we used qRT-PCR to determine the expression of genes in their metabolic pathways.Transcript abundances of three por genes in chlorophyll synthesis decreased whereas those of two CLH increased.The increased expression of VDE and ZEP was in consistence with the accumulation of zeaxanthin and antheraxanthin.Then we found eda3 lacked the stacked granal thylakoids under transmission electron microscope.Immunoblot analyses were used to determine the subcellular localization of ED A3.Our results demonstrated that ED A3 mainly exsits in the stroma thylakoids as PPD1 protein.This may explain the disordered organization of the thylakoids.Deficiency of ED A3 also causes some changes in PS?.The quantum yield of PS?,electron transport rate and photoprotection ability were damaged,as our measurements of the chlorophyll fluorecense parameters including Fv/Fm,DPS?,ETR and NPQ suggested.Interestingly,EDA3 also affects the gemale gametogenesis in embryo development,in addition to pigments metabolism.eda3 mutants have fewer and shorter siliques with aberrent seeds.Some ovelus were found to be arrested at the two-nuclear stage in the embryo sac.We found the expression level of two anaphase-promoting complex/cyclosome genes named APC7 and APC13 decreased.A distinct YFP signal were tested in the nucleus when EDA3-YFP fusion protein was transient-expressed in the protoplast.Overall,our preliminary results support that EDA3 regulates photosynthetic pigment metabolism in the chloroplast and participates in the embryo development in the nucleus at different develoment stages.