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. 2023 Jun 7;35(11):3973–4001. doi: 10.1093/plcell/koad164

Figure 3.

Figure 3.

Dying apical parts display contrasting patterns of primary metabolites. A) Metabolite distributions in spike tissue sections of cv. Bowman by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) imaging. Low levels of glutamine (Gln, m/z 147.1 ± 0.1 Da) and disaccharide (m/z 381.1 ± 0.1 Da) sugar towards the apical part can be observed in both W5.0 and W6.5 stages. A high level of asparagine (Asn, m/z 133.1 ± 0.1 Da) was found in the apical part of the section at stage W6.5. Scale bar 1 mm. The color bar shows the signal intensity of ions. B) Graphs show the absolute levels of soluble sugars (sucrose, fructose), sugar phosphate T6P, and AA Asparagine in different spike parts of Bowman. Plots show means ± Sd calculated from 3 to 5 biological replicates (Materials and Methods; Supplemental Data Set S2). Significance was tested using 2-way ANOVA with Tukey's multiple comparison test to evaluate the difference between apical, central, and basal positions at each stage (Supplemental Data Set S42). The y-axis represents absolute units of measurement. FW, fresh weight. C) Heatmap of primary metabolite changes during the spike growth phase. Colors represent the Z-transformed ratios of apical, central, and basal parts at each stage. Suc, sucrose; Glc, glucose; Fru, fructose; T6P, trehalose-6-phosphate; Asn, asparagine; Asp, aspartate; Arg, arginine; Ala, Alanine; Glu, glutamate; Gln, glutamine, Cys, cysteine, Met, methionine; Gly, glycine; Ser, serine; His, histidine; Val, valine; Leu, Leucine; Ile, isoleucine; Phe, phenylalanine; Tyr, tyrosine; Trp, tryptophan, Thr, threonine; Lys, lysine; GABA, gamma-aminobutyric acid; Pro, proline; 3-PGA, 3-Phosphoglyceric acid; PEP, phosphoenolpyruvate; Pry, pyruvate; 2-OG, 2-Oxoglutarate; AAAs, aromatic amino acids; BCAAs, branched-chain amino acids; TCA, tri-carboxylic acid; W, Waddington scale; cv., cultivar; PTD, pre-anthesis tip degeneration. The red asterisk points to the AAs and sugar enriched at high levels in the apical part during PTD.