A DOF Family Member,OBP2,Might Play A Role In The Process Of Chloroplast Biogenesis And Affect Photosynthesis

In higher plants,photosynthesis takes place mainly in chloroplasts.So,it is quite important to form intact and functional chloroplasts during the development of a plant.In the pursuit to gain more information of the regulation network on chloroplasts development and photosynthesis in Arabidopsis,we obtained a leaf color variegated mutant and named it Line 17 through the selection from Arabidopsis T-DNA insertion mutant pools.Using this "Forward Genetics" approach,we then analyzed the mutant Line 17 and proposed that the mutated gene in Line 17 might play a role in chloroplast development and affect photosynthesis in ArabidopsisWe found that there was a T-DNA insertion site in the promoter region of At1g07640,also named as OBP2,which encodes a DOF(DNA binding with One Finger)transcription factor.DOF proteins are a family of transcription factors which are plant-specific and belong to the family of zinc finger protein.The DOF transcription factors can be characterized by a highly conserved region of 52 amino acids contains a specific CX2CX21CX2C motif which binds to zinc ions.They bind specially to DNA sequences that contain a 5'-AAAG/CTTT-3' core while the flanking sequences also play a role in the binding capacity.DOF proteins can vary tremendously in their N-terminal and C-terminal region outside the DOF domain,which might enable them to specially bind to different regulators and participate in diverse regulatory processes.The DOF transcription factors are involved in multiple processes of plant development and metabolism,including seed germination,light regulation of genes involved in carbohydrate metabolism,plant defense mechanisms and so on.In this article,we focused on a DOF transcription factor,OBP2,and analyzed its role in chloroplast development and photosynthesis.The development of chloroplast can be a very complex process involves nuclear gene transcription,protein import and processing,chloroplast gene transcription and translation,protein folding and degradation,etc.Considering the leaf color variegation of Line 17,we performed pigment analysis and semi-thin section on it and found obvious decreases in both chlorophyll and beta-carotene content but no obvious change in chloroplast numbers in the mutant.Also,we discovered a lower photosynthesis capacity and a lower electron transport rate in Line 17.To find out how OBP2 affects the pigment amount and influences the photosynthesis in the mutant,we performed expression analysis on some related genes and did co-expression prediction in order to find more clues leading to further researches.