Arabidopsis sterol carrier protein-2 is required for normal development of seeds and seedlings

The Arabidopsis thaliana sterol carrier protein-2 (AtSCP2) is a small, basic and peroxisomal protein that in vitro enhances the transfer of lipids between membranes. AtSCP2 and all other plant SCP-2 that have been identified are single-domain polypeptides, whereas in many other eukaryotes SCP-2 domains are expressed in the terminus of multidomain polypeptides. The AtSCP2 transcript is expressed in all analysed tissues and developmental stages, with the highest levels in floral tissues and in maturing seeds. The expression of AtSCP2 is highly correlated with the multifunctional protein-2 (MFP2) involved in beta-oxidation. A. thaliana Atscp2-1 plants deficient in AtSCP2 show altered seed morphology, a delayed germination, and are dependent on an exogenous carbon source to avoid a delayed seedling establishment. Metabolomic investigations revealed 110 variables (putative metabolites) that differed in relative concentration between Atscp2-1 and normal A. thaliana wild-type seedlings. Microarray analysis revealed that many genes whose expression is altered in mutants with a deficiency in the glyoxylate pathway, also have a changed expression level in Atscp2-1.