Submitted to: Plant Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/18/2006
Publication Date: 12/10/2006
Citation: Kojima, M., Casteel, J., Miernyk, J.A., Thelen, J.J. 2006. The effects of down-regulating expression of Arabidopsis thaliana membrane-associated acyl-CoA binding protein 2 on acyl-lipid composition. Plant Science. 172:36-44. Interpretive Summary: The complete genome of the reference plant mouse-eared cress has been analyzed to predict the number of genes that could be involved in accumulation of seed oil. In one family of the gene products, two members were identified. It is impossible to accurately predict if one of the genes functions as a back-up or if it performs some specialized function. A method was used to eliminate expression of one of the genes, then detailed analysis of the plant oil composition was conducted. The resulting conclusion is that the second gene performs a specialized rather than back-up role. There was not, however, a significant increase in total oil, which indicates that this gene is not a good target for modification in oil-rich crop plants such as soybean. This information will be important to researchers for their attempts to modify seed composition in agricultural crops, and to other plant scientists who will try to design more efficient crop plants through either classical breeding or biotechnology.
Technical Abstract: Multiple classes of acyl-CoA binding proteins are encoded by plant genomes, including a plant-unique class of predicted integral membrane-proteins. Transcript analysis revealed that both of the integral membrane-acyl-CoA binding proteins of Arabidopsis thaliana, ACBP1 and ACBP2, are expressed in all organs. Expression of ACBP2 was highest in developing roots and flowers, and was four-fold greater than expression of ACBP1. Polyclonal antibodies against recombinant ACBP2 specifically recognized a Mr 47k protein that accumulated to similar levels in A. thaliana leaves, flowers, and siliques (0.05-0.07% total protein), but was two-fold more abundant in roots. To study the potential role(s) of ACBP2 in acyl-CoA metabolism, expression was downregulated using hairpin RNA interference (RNAi). Three RNAi lines with at least 70% reduced levels of the ACBP2 protein were analyzed, but displayed no gross alterations in growth or developmental phenotype. A systematic analysis of lipids from developing leaves by electrospray tandem-mass spectrometry revealed little change in the levels of the eight major lipid classes but significant changes in fatty acid composition were observed, particularly for the phospholipids. These data suggest a specialized rather than general role for ACBP2 in plant acyl-lipid metabolism.