Ultra-High α-Linolenic Acid Accumulating Developmental Defective Embryo was Rescued by Lysophosphatidic Acid Acyltransferase 2

For decades, genetic engineering approaches to produce unusual fatty acids (UFAs) in crops has reached a bottleneck, including reduced seed oil production and seed vigor. Currently, plant models in the field of research are primarily used to investigate defects in oil production and seedling development, while the role of UFAs in embryonic developmental defects remains unknown. In this study, we developed a transgenic Arabidopsis plant model, in which the embryo exhibits severely wrinkled appearance owing to α-linolenic acid (ALA) accumulation. RNA-seq analysis in the defective embryo suggested that brassinosteroid synthesis, fatty acid (FA) synthesis, and photosynthesis were inhibited, while FA degradation, endoplasmic reticulum (ER) stress, and oxidative stress were activated. Lipidomics analysis showed that ultra-accumulated ALA is released from Phosphatidylcholine (PC) as a free fatty acid (FFA) in cell, inducing severe ER and oxidative stress. Furthermore, we identified that overexpression of lysophosphatidic acid acyltransferase 2 (LPAT2) rescued the defective phenotype. In the rescue line, the pool capacity of the Kennedy pathway was increased, and the esterification of ALA indirectly to triacylglycerol (TAG) was enhanced to avoid stress. This study provides a plant model that aids in understanding the molecular mechanism of embryonic developmental defects, and generate strategies to produce higher levels of UFAs.

Keywords: Arabidopsis thaliana; Camelina sativa; embryo developmental defects; lysophosphatidic acid acyltransferase 2; oil production; unusual fatty acids.