Sacha inchi (Plukenetia volubilis L.), also known as “inca inchi” or “inca peanut”, is a perennial, oleaginous, woody twining vine of the Euphorbiaceae family, native to the tropical Peruvian jungles at altitudes between 200 and 1,500 m. Its seed oil is rich in α-linolenic acid (ALA), a kind of n-3 fatty acids with many health benefits. Why sacha inchi seeds accumulate such high quantities of ALA is unknown. Investigating the profiles of lipid ALA accumulation in sacha inchi seeds might provide insights into understanding the physiological and molecular mechanisms underlying ALA biosynthesis to facilitate the exploration and utilization of oilseed crop resources in agriculture.
Dr. LIU Aizhong and his student of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a preliminary research on sacha inchi seed development. They characterized a time-course for seed development and storage reserve (in particular lipids and ALA) accumulation during sacha inchi seed development, and investigated the temperature effect on lipid and ALA accumulation of sacha inchi seeds. Further, based on their previous gene (expression sequence tags) EST library, they inspected temporal expression profiles of 17 lipid genes involved in different steps of the pathway leading to ALA-based oil biosynthesis within sacha inchi developing seeds using quantitative real-time PCR technology.
Sacha inchi blooms and sets fruit throughout a year in Xishuangbanna area. The effects of temperature on total oil content and on fatty acid composition of lipid fractions of sacha inchi seeds were determined in two distinct seasons. The results showed that total oil content decreased in the cool season, suggesting that the low environmental temperature is not beneficial to lipid accumulation in sacha inchi seeds; while unsaturated fatty acid and linolenic acid (USAF) concentrations increased, indicating that the low environmental temperature was favorable to the accumulation of USFA in sacha inchi seeds.
The results provided integrative information for understanding ALA biosyntheses in sacha inchi seeds and identifying rate-limiting enzyme genes which are critical to metabolic engineering of transgenic oilseeds for high ALA production.
The study entitled “Expression of Genes Controlling Unsaturated Fatty Acids Biosynthesis and Oil Deposition in Developing Seeds of Sacha Inchi (Plukenetia volubilisL.)” has been published in Lipids.
