No abstract

Histone modifications are of paramount importance during plant development. Investigating chromatin remodeling in developing oilseeds sheds light on the molecular mechanisms controlling fatty acid metabolism and facilitates the identification of new functional regions in oil crop genomes. The present study characterizes the epigenetic modifications H3K4me3 in relationship with the expression of fatty acid-related genes and transcription factors in developing sunflower seeds. Two master transcriptional regulators identified in this analysis, VIV1 (homologous to Arabidopsis ABI3) and FUS3, cooperate in the regulation of WRINKLED 1, a transcriptional factor regulating glycolysis, and fatty acid synthesis in developing oilseeds.

No abstract

Koelreuteria paniculata is a deciduous tree, popular in temperate regions for its ornamental value, which accumulates unusual cyanolipids in its seeds. The seed oil of this plant is rich in the unusual cis-11-eicosenoic fatty acid (20:1, or gondoic acid), a monounsaturated oil of interest to the oleochemical industry. In higher plants, de novo fatty acid biosynthesis takes place in the plastids, a process that is terminated by hydrolysis of the thioester bond between the acyl moiety and the ACP by acyl-ACP thioesterases. The specificity of acyl-ACP thioesterases is fundamental in controlling the fatty acid composition of seed oil. To determine the mechanisms involved in fatty acid biosynthesis in K. paniculata seeds, we isolated, cloned and sequenced two cDNAs encoding acyl-ACP thioesterases in this plant, Kp FatA and Kp FatB. Both of them were expressed heterologously in Escherichia coli and characterized with different acyl-ACP substrates. The K. paniculata FatB2 displayed unusual substrate specificity, so that unlike most FatB2 type enzymes, it displayed preference for oleoyl-ACP instead of palmitoyl-ACP. This specificity was consistent with the changes in E. coli and N. benthamiana fatty acid composition following heterologous expression of this enzyme. Kp FatB also showed certain genetic divergence relative to other FatB-type thioesterases and when modelled, its structure revealed differences at the active site. Together, these results suggest that this thioesterase could be a new class of FatB not described previously.