Trends in Plant Science
Volume 25, Issue 8, August 2020, Pages 719-722
Journal home page for Trends in Plant Science

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Pectin Drives Cell Wall Morphogenesis without Turgor Pressure

https://doi.org/10.1016/j.tplants.2020.05.007Get rights and content

How the plant cell wall expands and forms shapes is a long-standing mystery. Traditional thought is that turgor pressure drives these processes. However, a recent study by Haas and colleagues shows for the first time that the expansion of pectin homogalacturonan nanofilaments drives morphogenesis without turgor pressure in plant epidermal cells.

Section snippets

Plants Have an Intricate Cell Wall with Diverse Functions

The cell wall is the rigid and semipermeable biphasic outer layer of plant cells. It is an essential component of plant cells and represents the major difference between plant and animal cells (animal cells lack a cell wall). In addition to its major function as a framework for the cell to prevent overexpansion, the plant cell wall (i) controls and directs cell growth, (ii) provides mechanical support and strength for the plant, (iii) mediates cell communication, (iv) plays a significant role

Nanofilament Structure of Pectin Homogalacturonan

Pectins constitute a diverse class of polysaccharides characterized by 1,4-linked α-D-galactosyluronic acid (GalpA, also known as galacturonic acid), including homogalacturonan (HG), xylogalacturonan (XGA), apiogalacturonan, rhamnogalacturonan I (RGI), and rhamnogalacturonan II (RGII). The ratios of these pectins is variable. HG (60%) is the most abundant, followed by RGI, and together these two classes constitute >75% of total pectins [4]. Pectins in the extracellular matrix were previously

Demethylation-Mediated Pectin Nanofilament Inflation Drives Plant Cell Anisotropic Growth without Turgor Pressure

Pectin methylation and demethylation play important roles in pectin structure and function. Pectin is biosynthesized in a methylated form in Golgi vesicles, and is generally converted into the demethylated form on insertion into the cell wall [6]. To study the behavior of methylated and demethylated HG, and their impact on cell wall shape and cell growth, Haas and colleagues first generated transgenic arabidopsis plants overexpressing either PECTIN METHYLESTERASE (PME) or PECTIN METHYLESTERASE

Concluding Remarks and Future Perspectives

This is the first observation that pectin forms nanofilament structures in intact cells. Based on the observation and their FEM model, Haas et al. demonstrate that HG methylation and demethylation result in switching of quaternary structures of HG nanofilaments, from a hexagonal to a rectangular lattice in the cell wall, leading to HG filament expansion, and that this is the primary force that shapes the cell wall and cell growth (Figure 1B) [3]. However, there are still many questions to be

Acknowledgments

We greatly appreciate Dr Claudia Jolls for her excellent comments and for proofreading this paper. D.Z. is supported by the National Natural Science Foundation of China (31172257), the Science Research Project in Henan Province of China (192102110174), and the Talent Project of Henan Agriculture University. B.Z. is supported in part by Cotton Incorporated and the National Science Foundation (award 1658709).

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