Metabolomic Profiling of Drought-Responsive Pathways in Sorghum bicolor
DOI:
https://doi.org/10.5281/zenodo.22687865Keywords:
Sorghum bicolor, drought stress, metabolomics, LC-MS/GC-MS, osmolytes, dhurrin, phenylpropanoid pathwayAbstract
Sorghum is often held up as the cereal best equipped to cope with a drying climate, yet the metabolic changes
underlying that reputation have rarely been mapped at the resolution modern mass spectrometry now allows. We
combined untargeted LC-MS and GC-MS profiling to track the leaf and root metabolomes of two sorghum
genotypes with contrasting field reputations for drought tolerance, BTx642 (stay-green) and Tx7000
(drought-sensitive check), across a controlled progressive soil dry-down and a subsequent re-watering period.
Roughly 640 polar and semi-polar metabolite features were confidently annotated across both tissues and
platforms. Both genotypes accumulated proline, raffinose and galactinol as water potential fell, but BTx642
reached severalfold higher peak concentrations of these osmolytes without the concurrent depletion of TCA-cycle
intermediates that we observed in Tx7000, suggesting better-preserved central carbon metabolism under stress
rather than a purely stronger osmotic response. The two genotypes diverged most sharply in the phenylpropanoid
branch: BTx642 leaves showed a pronounced, drought-specific rise in flavonoid glycosides and a transient dip in
dhurrin, the constitutive cyanogenic glucoside characteristic of sorghum, that recovered fully within 48 hours of
re-watering. Root metabolomes were less genotype-differentiated than leaves but showed a consistent
stress-associated increase in phenolic acids implicated in root suberisation. Pathway enrichment placed flavonoid
biosynthesis, the TCA cycle and raffinose-family oligosaccharide metabolism among the most significantly altered
modules in both genotypes, with the magnitude and persistence of the response, rather than its qualitative identity,
distinguishing stay-green from sensitive sorghum. These results sharpen the metabolic phenotype behind
sorghum drought tolerance and nominate a small panel of biomarkers, including the raffinose-to-sucrose ratio and
dhurrin recovery kinetics, for screening breeding populations ahead of costly field trials.
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