Metabolomic shifts in Brassica napus lines with enhanced BnPLC2 expression impact their response to low temperature stress and plant pathogens

Abstract

Phosphatidylinositol-specific phospholipase C2 (PLC2) is a signaling enzyme with hydrolytic activity against membrane-bound phosphoinositides. It catalyzes the cleavage of phosphatidylinositol(4,5)bisphosphate (PtdIns(4,5)P2) into two initial second messengers, myo-inositol-1,4,5-trisphosphate (InsP3) and diacylglycerol (DAG). The former, as well as its fully phosphorylated derivative, myo-inositol-1,2,3,4,5,6-hexakisphosphate (InsP6), play a major role in calcium signaling events within the cell, while DAG may be used in the regeneration of phospholipids or as a precursor for phosphatidic acid (PA) biosynthesis, an important signaling molecule involved in both biotic and abiotic types of stress tolerance. Overexpression of the gene for Brassica napus phospholipase C2 (BnPLC2) in Brassica napus has been shown to enhance drought tolerance, modulate multiple genes involved in different processes and favorably affect hormonal levels in different tissues. We, therefore, undertook the current study with a view to examining, at the metabolome level, its effect on both abiotic (low temperature) and biotic (stem white rot disease) types of stress in canola. Thus, while transgenic plants exhibited a significant rise in maltose levels and a concomitant elevation in some unsaturated free fatty acids (FFAs), glycerol, and glycerol 3-phosphate under subzero temperatures, they accumulated high levels of raffinose, stachyose and other sugars as well as some flavonoids under acclimatization conditions. Collectively, overexpression of BnPLC2 appears to have triggered different metabolite patterns consistent with its abiotic and, to a limited extent, biotic stress tolerance phenotypes.