Patterns of gene expression in developing Arabidopsis seeds during storage lipid synthesis

Abstract

We have used microarrays to explore factors that regulate the overall partitioning of seed reserves into storage compounds, and particularly the accumulation of seed oil. Arabidopsis can be used as a model to study lipid synthesis in oil crops, because triacylglycerides are the major reserve in its seeds. To this end, we have produced microarrays containing about 5000 clones selected from a developing Arabidopsis seed-specific cDNA library, and used them to study gene expression profiles during seed filling. This approach allowed us to simultaneously compare mRNA levels of genes for fatty acid synthesis (FAS), storage proteins, glycolysis, etc. from the same material. Analysis of expression profiles at different stages of development identified about 2000 genes whose expression changed significantly during the accumulation of the storage reserves. Several genes encoding FAS enzymes (acetyl-CoA carboxylase subunits, KAS I, and acyl-carrier protein) showed coordinated expression. Typically, the highest gene expression coincided with the most active storage lipid accumulation, and then decreased rapidly. This pattern was distinctly different from that for many glycolytic enzymes, storage proteins and oleosins, as well as some fatty acid modifying enzymes (FAD3 and FAE1). These observations imply different regulatory controls over gene expression for different storage components in seeds. We also identified several transcription factors, kinases and phosphatases, whose expression changed during the seed development, and which may be involved in the regulation of the storage compound synthesis. Moreover, cluster analysis of the expression profiles established distinct groups of co-regulated genes.