Fig. 13

Proposed lipid metabolism pathways suggesting the mechanism that maybe associated with the altered lipid mediators and disease tolerance or susceptibility in soybean cultivars (OX760-6 and Conrad) following inoculation with P. sojae. a The most significantly altered root lipids in soybean cultivars in response to infection with P.sojae; and (b) The most significantly altered stem lipids in soybean cultivars in response to P. sojae infection. In the Kennedy pathway fatty acyl-CoA and coenzyme A begins with the sequential acylation of GPATs and LPAATs utilizing fatty acyl-CoA to biosynthesis the central precursor PA through which other downstream GPLs are produced. GLPs are produced through hydrolysis of the phosphate group in PA, and this PA then dephosphorylated through PAP to generate DG. The DG acts as a precursor for biosynthesis of TG via DGAT or PDAT transferring the sn-2 fatty acyl group from GPLs to DG, producing TG. Biosynthesis of IPP and DMAPP through mevalonate (MVA) pathway, and they act as precursors for phytosterol synthesis. The altered lipidome observed in this study suggest DG and PA mediated lipid signalling impacting phytosterol anabolism appears to be the strategy used by tolerant soybean cultivars to successfully limit infection and colonization by P.sojae. The following molecular species are suggested as unique lipid biomarkers in the ORI vs CRI and CSI vs OSI networks that could potentially discriminate tolerance interations in the soybean-P.sojae pathosystem: TG(18:3/18:2/23:0), TG(10:0/10:0/10:0), TG(10:0/10:0/14:0), DG(18:3/18:3), DG(16:0/18:3) and DG(24:0/18:2). PLD = phospholipase D, DGK = diacylglycerol kinase, LPAAT = lysophosphatidic acid acylteransferase, PAP = phosphatic acid phosphatase, G3P = glycerol-3-phosphate, DGAT = diacylglycerol acyltranferase, GPAT = Glycerol‐3‐phosphate acyltransferase, PDAT = phospholipid:diacylglycerol acyltransferases, PSS1 = phosphatidylserine synthase-1, PGP = glycerol-3-phosphate phosphatase, PAP = phosphatidic acid phosphatase, IPP = isopentenyl pyrophosphate, DMAPP = dimethylallyl pyrophosphate, MVA = mevalonic acid, PIP3 = 1-phosphatidylinositol-4-phosphate 5-kinase, CoASH = coenzyme A, Chop = cholinephosphotransferase and cho = choline. ORI = root of susceptible inoculated, CRI = root of tolerant inoculated, OSI = stem of susceptible inoculated, CSI = stem of tolerant inoculated, GPLs = glycerophospholipids, GLs = glycerolipids, LPA = lysophosphatidic, PA = phosphatidic acid, PC = phosphatidylcholine, PG = phosphatidyl glycerol, PI = phosphatidylinositol, PS = phosphatidylserine, DG = diacylglycerol, TG = triacylglycerol and PST = phytosterols