(A) Medial longitude jojoba seed section with labeled seed tissues and structures. Scale bar, 1.0 mm. (B) MALDI-MS image of the major molecular species of WE 42:2 (m/z 655.579, WE 22:1/20:1), which was enriched in the cotyledonary tissues. (C) MALDI-MS image of the major molecular TAG species TAG 62:3 (m/z 1035.872, TAG 20:1/20:1/22:1) highly enriched in the embryonic axis. (D) Composite MALDI-MS image of WE 42:2 (red) and TAG 62:3 (green) demonstrating the differential enrichment of WEs and TAGs in jojoba seeds. In images above, color scale (ion intensity) for each lipid was adjusted to emphasize distribution and does not represent absolute amounts of lipid. Mass tolerance for MALDI-MS images was set to 4 parts per million. (E and F) Total ion signal from each of the cotyledons and embryonic axis was acquired for these tissue areas of the MALDI-MS image. Signal was normalized to the total ion count and then to the number of pixels in the embryonic axis or cotyledons, respectively. The overall WE (E) and TAG (F) content of virtually “dissected” cotyledon and embryonic axis tissues was calculated by summing the intensities of all detected WE and TAG molecular species. Student’s t test was used to calculate significance where *** is P < 0.001. (G) Depiction of metabolic pathways and genes leading to WE and TAG biosynthesis in jojoba. Colored boxes (blue to magenta color scale) adjacent to gene names indicate gene expression bias toward embryonic axis tissues (blue) or toward cotyledon tissues (magenta) and represent a log₂ fold change of expression levels (n = 5, *q < 0.05, **q < 0.01, ***q < 0.001). Acyl-CoA, acyl coenzyme A; GPAT, glycerol-3-phosphate acyltransferase; PAP, phosphatidic acid phosphatase. (H) Heat map of gene expression levels of genes involved in glycerolipid and WE synthesis across different jojoba seed tissues and developmental stages. FATB, fatty acyl-ACP thioesterase B; FATA, fatty acyl-ACP thioesterase A; SAD, stearoyl-ACP desaturase; LPAT, lysophosphatidyl acyltransferase; PA phosphatidic acid; DAG, diacylglycerol; FFA, free fatty acid; G3P, glycerol 3 phosphate; LPA, lysophosphatidic acid; DGAT, diacylglycerol acyltransferase; PDAT, phospholipid:diacylglycerol acyltransferase; PDCT, phosphatidylcholine:diacylglycerol cholinephosphotransferase; PLDa, phospholipase D alpha; PLA2a, phospholipase A2 alpha; LPCAT, lysophosphatidylcholine acyltransferase; FAR, fatty acyl-CoA reductase; KCS, ketoacyl-CoA synthase; FAE, fatty acid elongation; PC, phosphatidylcholine; LPC, lysophosphatidylcholine; CO, cotyledons; EA, embryonic axis; SC, seed coat; WS, whole seed; EDS, early developing seed; MDS, mid developing seed; LDS, late developing seed; DS, dry seed; L, leaf. Photo credit: Drew Sturtevant, UNT.