Title : Major sugars, metabolites, proteins and their role in storage accumulation of Pongamia pinnata seeds, a potential biofuel tree species
The present study analyzed the dynamic changes in sugars, metabolites and key proteins during the seed development of Pongamia pinnata L. (Family: Fabaceae) with a particular focus on lipid biosynthesis and oil accumulation. The developing seeds were collected at four different stages: 120 (stage 1), 180 (stage 2), 240 (stage 3) and 300 (stage 4) days after flowering (DAF), representing S1, S2, S3 and S4 respectively. The analysis of seed pigments and mRNA expression patterns of key photosynthetic genes confirmed the photo-autotrophic behavior of P. pinnata seed during the initial stages of development. The metabolite profiling of developing P. pinnata seeds also revealed differentially expressed sugars, amino acids, free fatty acids and organic acids. Proteins related to development, energy metabolism, lipid accumulation as well as stress responses were documented through MALDI-TOF-MS/MS analysis. The structure and pattern of oil body accumulation at each stage of seed development were determined by electron and confocal microscopy of the cotyledonary sections. The thin layer chromatogram of P. pinnata oil revealed higher amount of Triacylglycerides and the fatty acid profile of extracted Triacylglycerides showed a rapid increase in oleic acid (C18:1) at S3 and S4. The objective of the current study is to profile the metabolome and identification of key regulatory proteins in different developing stages of P. pinnata seed and their role in FA accumulation. In addition, the photosynthetic behavior of the P. pinnata seed also have been identified which will help in understanding the carbon influx to FA biosynthesis. Our results will deepen the knowledge on metabolic regulation of P. pinnata seed development and oil accumulation which is important for further metabolic engineering of this potential biofuel feedstock for different industrial and agricultural applications. The outcomes reveal new insights into the complex oleogenic metabolism during P. pinnata seed development at macro level.