TY - JOUR

T1 - Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging of Metabolites during Sorghum Germination

AU - Montini, Lucia

AU - Crocoll, Christoph

AU - Gleadow, Roslyn M.

AU - Motawia, Mohammed Saddik

AU - Janfelt, Christian

AU - Bjarnholt, Nanna

PY - 2020

Y1 - 2020

N2 - Matrix-assisted laser desorption/ionization-mass spectrometry imaging reveals that biosynthesis and recycling of the plant defense compound dhurrin are key events during sorghum grain germination.Dhurrin is the most abundant cyanogenic glucoside found in sorghum (Sorghum bicolor)where it plays a key role in chemical defense by releasing toxic hydrogen cyanide upon tissue disruption. Besides this well-established function, there is strong evidence that dhurrin plays additional roles, e.g. as a transport and storage form of nitrogen, released via endogenous recycling pathways. However, knowledge about how, when and why dhurrin is endogenously metabolized is limited. We combined targeted metabolite profiling with matrix-assisted laser desorption/ionization-mass spectrometry imaging to investigate accumulation of dhurrin, its recycling products and key general metabolites in four different sorghum lines during 72 h of grain imbibition, germination and early seedling development, as well as the spatial distribution of these metabolites in two of the lines. Little or no dhurrin or recycling products were present in the dry grain, but their de novo biosynthesis started immediately after water uptake. Dhurrin accumulation increased rapidly within the first 24 h in parallel with an increase in free amino acids, a key event in seed germination. The trajectories and final concentrations of dhurrin, the recycling products and free amino acids reached within the experimental period were dependent on genotype. Matrix-assisted laser desorption/ionization-mass spectrometry imaging demonstrated that dhurrin primarily accumulated in the germinating embryo, confirming its function in protecting the emerging tissue against herbivory. The dhurrin recycling products, however, were mainly located in the scutellum and/or pericarp/seed coat region, suggesting unknown key functions in germination.

AB - Matrix-assisted laser desorption/ionization-mass spectrometry imaging reveals that biosynthesis and recycling of the plant defense compound dhurrin are key events during sorghum grain germination.Dhurrin is the most abundant cyanogenic glucoside found in sorghum (Sorghum bicolor)where it plays a key role in chemical defense by releasing toxic hydrogen cyanide upon tissue disruption. Besides this well-established function, there is strong evidence that dhurrin plays additional roles, e.g. as a transport and storage form of nitrogen, released via endogenous recycling pathways. However, knowledge about how, when and why dhurrin is endogenously metabolized is limited. We combined targeted metabolite profiling with matrix-assisted laser desorption/ionization-mass spectrometry imaging to investigate accumulation of dhurrin, its recycling products and key general metabolites in four different sorghum lines during 72 h of grain imbibition, germination and early seedling development, as well as the spatial distribution of these metabolites in two of the lines. Little or no dhurrin or recycling products were present in the dry grain, but their de novo biosynthesis started immediately after water uptake. Dhurrin accumulation increased rapidly within the first 24 h in parallel with an increase in free amino acids, a key event in seed germination. The trajectories and final concentrations of dhurrin, the recycling products and free amino acids reached within the experimental period were dependent on genotype. Matrix-assisted laser desorption/ionization-mass spectrometry imaging demonstrated that dhurrin primarily accumulated in the germinating embryo, confirming its function in protecting the emerging tissue against herbivory. The dhurrin recycling products, however, were mainly located in the scutellum and/or pericarp/seed coat region, suggesting unknown key functions in germination.

KW - P-HYDROXYPHENYLACETIC ACID

KW - CYANOGENIC GLYCOSIDES

KW - FROZEN-SECTIONS

KW - BARNYARD GRASS

KW - HARD TISSUES

KW - BIOSYNTHESIS

KW - GERMINATION

KW - DHURRIN

KW - ENDOSPERM

KW - PLANTS

U2 - 10.1104/pp.19.01357

DO - 10.1104/pp.19.01357

M3 - Journal article

C2 - 32350122

VL - 183

SP - 925

EP - 942

JO - Plant Physiology

JF - Plant Physiology

SN - 0032-0889

IS - 3

ER -