Metabolic Profiling with Gas Chromatography–Mass Spectrometry and Capillary Electrophoresis–Mass Spectrometry Reveals the Carbon–Nitrogen Status of Tobacco Leaves Across Different Planting Areas

The
interaction between carbon (C) and nitrogen (N) metabolism
can reflect plant growth status and environmental factors. Little
is known regarding the connections between C–N metabolism and
growing regions under field conditions. To comprehensively investigate
the relationship in mature tobacco leaves, we established metabolomics
approaches based on gas chromatography–mass spectrometry (GC–MS)
and capillary electrophoresis–time-of-flight–mass spectrometry
(CE–TOF–MS). Approximately 240 polar metabolites were
determined. Multivariate statistical analysis revealed that the growing
region greatly influenced the metabolic profiles of tobacco leaves.
A metabolic correlation network and related pathway maps were used
to reveal the global overview of the alteration of C–N metabolism
across three typical regions. In Yunnan, sugars and tricarboxylic
acid (TCA) cycle intermediates were closely correlated with amino
acid pools. Henan tobacco leaves showed positive correlation between
the pentose phosphate pathway (PPP) intermediates and C-rich secondary
metabolism. In Guizhou, the proline and asparagine had significant
links with TCA cycle intermediates and urea cycle, and antioxidant
accumulation was observed in response to drought. These results demonstrate
that combined analytical approaches have great potential to detect
polar metabolites and provide information on C–N metabolism
related to planting regional characteristics.