Gene expression related to free fatty acid synthesis in physic nut Jatropha curcas L. kernel by proteomics technique analysis

Abstract

Jatropha curcas L. is one of economic important crops used for its seed oil which can substitute for diesel. Free fatty acid profiles and proteins profiles of J. curcas kernel during development were studied. Developmental seeds were divided into 8 stages based on morphology. Free fatty acid was analyzed using gas chromatography. The results suggested that free fatty acid levels were changed at all stages of development from stage I to stage VIII. The major free fatty acid was oleic acid and the minor free fatty acids included linoleic acid, palmitic acid, and stearic acid. Furthermore, the protein profiles determined by proteomics technique indicated that 245 proteins were differentially expressed during the seed development such as proteins related to seed development (AP2 domain-containing protein and late embryogenesis abundant protein), proteins related to free fatty acid synthesis (acetyl CoA carboxylase and phosphoenolpyruvate carboxylase), and proteins related to fruit ripening (ACC oxidase and ACC deaminase). Moreover, a protein related to toxicity (curcin), that was only found in J. curcas was discovered. Real-time RT PCR was employed in a study of proteins involved in the biosynthesis of free fatty acids. These proteins included acetyl CoA carboxylase (ACCase), phosphoenolpyruvate carboxylase (PEPC), mercaptopyruvate sulfurtransferase (MST) and 4-coumarate: coenzyme A ligase (CMCoA). The results revealed that the relative mRNA expression level of each gene was altered in a similar pattern with regard to the amount of most free fatty acids. The decreased level of free fatty acids from stage IV to stage VI may caused by β-oxidation metabolism to generate energy for other metabolism. Additionally, intermediate substances from β-oxidation process may be used in flavonoid biosynthesis.