Spatiotemporal Systems Biology Reveals Unique Cell-Type-Specific Carbon Metabolism Responses to Combined Abiotic Stresses in Poplar

Central carbon metabolism plays a vital role in maintaining osmotic balance and energy stability under abiotic stress. However, the coordination of this reprogramming across various leaf cell types under combined stress conditions is not well understood. To address this knowledge gap, researchers employed an integrated spatial systems biology approach to gain a comprehensive, cell-type specific, multi-omics perspective on the responses of hybrid poplar (Populus tremula x P. alba) to single and combined abiotic stresses.

The study analyzed palisade and vascular cells of leaves exposed to water deficit, salinity, heat, or a combination of all three stressors. By isolating these cells using laser-capture microdissection, the researchers conducted cell-type resolved proteomics, transcriptomics, MALDI mass spectrometry imaging, and GC MS metabolomics.

The combined stress treatment significantly upregulated carbon metabolism, pentose phosphate pathway, and glyoxylate cycle proteins in palisade cells. Specifically, two glyceraldehyde-3-phosphate dehydrogenase (GAPDH) isoforms were found to be upregulated by 8.5 to 12.5 times, while no such increase was observed in vascular cells.

Further analysis of protein co-abundance networks revealed a significant association between GAPDH and inositol monophosphatase 3 (IMP3), suggesting coordinated regulation of sugar alcohol biosynthesis. Spatial metabolomics data indicated an accumulation of glyceraldehyde-3-phosphate (GA3P) and a decline in 3-phospho-D-glyceroyl phosphate (3PGP), the upstream gluconeogenic substrate of GAPDH, under combined stress conditions. This correlated with elevated levels of sugar alcohols.

These findings demonstrate that combined abiotic stress triggers a palisade-specific reprogramming of central carbon metabolism, in which GAPDH directs carbon flux towards gluconeogenesis and sugar alcohol biosynthesis. This coordinated shift represents a mechanistic pathway that could potentially be targeted to engineer improved plant tolerance to multifactorial stress conditions.