Heterologous Expression of the Plastid Glycerolipid Acyltransferase AtATS1 Negatively Regulates Salt Stress Tolerance in Rapeseed (Brassica napus)

Plastid-localized glycerol‑3‑phosphate acyltransferase (ATS1) catalyzes the initial acylation step in the prokaryotic branch of glycerolipid biosynthesis and is pivotal for membrane lipid remodeling. In this study, we investigated the role of Arabidopsis thaliana ATS1 (AtATS1) in salt tolerance using transgenic Brassica napus lines overexpressing AtATS1 and wild-type plants. Under 150 mM salt stress, AtATS1-overexpressing lines exhibited significantly compromised tolerance, characterized by severe growth inhibition and cotyledon abscission compared to wild-type plants. Physiological assays further revealed that despite a hyper-induction of antioxidant enzymes (SOD and POD), the transgenic lines suffered from excessive reactive oxygen species (ROS) accumulation and elevated malondialdehyde (MDA) levels, indicating a failure to maintain redox homeostasis. Transcriptomic analysis demonstrated that AtATS1 overexpression disrupts the stress response by misallocating metabolic resources toward glucosinolate biosynthesis and constitutively repressing the MAPK signaling cascade (including WRKY42, MPK15, and MEKK1). In conclusion, these findings identify AtATS1 as a negative regulator of salt tolerance in B. napus. This study provides new insights into the link between lipid metabolism and abiotic stress responses and highlights the need for careful modulation of glycerolipid biosynthesis when engineering salt-resilient rapeseed varieties.