Chromatography Reveals Galactan's Role in Plant Cell Growth

Pectic galactan is a sugar chain found in plant cell walls—specifically a side branch on a larger pectin molecule called rhamnogalacturonan-I, made up of linked galactose sugar units. Scientists think this sugar chain plays several roles in how plant cell walls are built and how they behave, depending on the stage of plant growth.

Researchers recently examined the role of galactan in pea plants. First, they examined pea stems that were elongating (growing longer) at different rates due to the plant hormone auxin, checking for changes in cell wall makeup. Using glycan profiling to detect specific sugar structures (via an antibody called LM5), the team found more galactan in the outer, more curved side of the stem—the side that was stretching and growing faster. The researchers then confirmed this result using two additional methods: monosaccharide composition analysis to investigate the individual sugar building blocks in the wall, and epitope detection chromatography (EDC) to determine whether the differences observed in galactan levels are due to there being more or less galactan present overall, or whether the galactan chains themselves are structurally different—or connected differently to other parts of the cell wall. A paper based on this research was published in the journal Plant Molecular Biology.¹

Why Must the Plant Cell Wall Change for Cells to Elongate?

The cell wall is a special structure that surrounds and supports plant cells, acting as their main line of defense against germs and outside environmental threats.^2,3Because it is made up of many different materials arranged in a complex 3D structure, the cell wall can take part in a wide range of jobs within the cell.⁴ Cells need to be able to stretch and grow longer for a plant to develop properly. But since the cell wall (the tough outer layer surrounding the cell) is stiff, it must loosen up or change to let the cell expand. Exactly how and how much it changes depends on the type of cell and what stage of growth or development the plant is in.^3,5

The research team chose to study pea plants (Pisum sativum, also recently renamed Lathyrus oleraceus) for a few practical reasons. Peas are easy to work with experimentally—they respond well to treatment with the hormone auxin, and they provide plenty of plant material to analyze cell wall makeup. In addition, there is already a reliable, well-tested method available for using virus-induced gene silencing (VIGS) in peas, which made it easier to turn down the activity of specific genes for the study.⁶ “This,” write the authors of the paper,¹ “provided an opportunity to investigate the roles of different cell wall components in elongation.”

What Happens to Pea Plant Development and Cell Wall Composition When Galactan Synthesis is Genetically Disrupted?

To test what happens when galactan production is disrupted in pea plants, the research team used the virus-induced gene silencing (VIGS) technique to turn down the activity of a specific gene, PsGALS3. This gene is the pea version of a gene family in Arabidopsis (GT92) that makes enzymes responsible for building galactan chains, and it's normally switched on by the plant hormone auxin.¹

Plants with this gene silenced grew poorly, having serious problems elongating and developing their leaves and stems. Using a cell wall analysis method called microarray polymer profiling (MAPP), the researchers found that as galactan levels dropped, another cell wall component, a protein called extensin, increased instead. This finding was double-checked by directly staining and viewing the plant tissue under a microscope, which confirmed the extensin increase.¹

“Our results,” write the authors of the paper,¹ “provide new evidence linking galactan to cell and organ expansion.”

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References

• Guo, X.; Kumar, A.; Johansen, I. E. et al. Loss of Galactan Synthesis in Pea (Pisum sativum) Causes Defects in Organ Expansion and Is Associated with Increased Extensin Content. Plant Mol Biol. 2026, 116 (5), 94. DOI: 10.1007/s11103-026-01759-x
• Geitmann, A. Plant Cell Walls: Research Milestones and Conceptual Insights. CRC Press, 2023.
• 3.Cosgrove, D. J. Structure and Growth of Plant Cell Walls. Nat Rev Mol Cell Biol. 2024, 25 (5), 340-358. DOI: 10.1038/s41580-023-00691-y
• 4.Zhang, L.; Gao, C.; Gao, Y. et al. New Insights into Plant Cell Wall Functions. J Genet Genomics 2025, 52 (11), 1308-1324. DOI: 10.1016/j.jgg.2025.04.013
• Labavitch, J. M. Cell Wall Turnover in Plant Development. Annu Rev Plant Physiol. 1981,32, 385-406. DOI: 10.1146/annurev.pp.32.060181.002125
• 6.Grønlund, M.; Olsen, A.; Johansen, E. I. et al. Protocol: Using Virus-induced Gene Silencing to Study the Arbuscular Mycorrhizal Symbiosis in Pisum sativum. Plant Methods 2010, 6, 28. DOI: 10.1186/1746-4811-6-28

The research team chose to study pea plants (Pisum sativum, also recently renamed Lathyrus oleraceus) for a few practical reasons. Peas are easy to work with experimentally—they respond well to treatment with the hormone auxin, and they provide plenty of plant material to analyze cell wall makeup. In addition, there is already a reliable, well-tested method available for using virus-induced gene silencing (VIGS) in peas, which made it easier to turn down the activity of specific genes for the study.⁶ “This,” write the authors of the paper,¹ “provided an opportunity to investigate the roles of different cell wall components in elongation.”