Low and high temperatures promote docosahexaenoic acid accumulation in Crypthecodinium sp. SUN by regulating the polyunsaturated fatty acid synthase pathway and the expression of saturated fatty acid preferred diacylglycerol acyltransferases.

Low (15 °C) and high (35 °C) temperatures significantly increased DHA as a percentage of total fatty acids (TFAs) to 43.6 % and 40.46 %, respectively (1.28- and 1.18-fold of that at 25 °C, respectively). The incompleteness of the FAS pathway indicates that DHA synthesis does not occur via this pathway. Meanwhile, Comparative transcriptome analysis showed that the PUFA synthase pathway might be responsible for DHA synthesis in C. sp. SUN. Additionally, the three diacylglycerol acyltransferases all had a substrate preference for saturated fatty acid (SFA)-CoA, which also contributed to the decreased SFA and increased DHA at both low and high temperatures. Additionally, WGCNA analysis identifies key regulatory genes that may be involved in temperature-regulated DHA proportion. The findings of this study indicate the mechanisms of temperature-regulated DHA accumulation in C. sp. SUN and shed light on the manipulation of DHA proportion by changes in temperature.