The Plant Cell Wall: A Complex and Dynamic Structure As Revealed by the Responses of Genes under Stress Conditions

Abstract

The plant cell wall has a diversity of functions. It provides a structural framework to support plant growth and acts as the first line of defense when the plant encounters pathogens. The cell wall must also retain some flexibility, such that when subjected to developmental, biotic, or abiotic stimuli it can be rapidly remodeled in response. Genes encoding enzymes capable of synthesizing or hydrolyzing components of the plant cell wall show differential expression when subjected to different stresses, suggesting they may facilitate stress tolerance through changes in cell wall composition. In this review we summarize recent genetic and transcriptomic data from the literature supporting a role for specific cell wall-related genes in stress responses, in both dicot and monocot systems. These studies highlight that the molecular signatures of cell wall modification are often complex and dynamic, with multiple genes appearing to respond to a given stimulus. Despite this, comparisons between publically available datasets indicate that in many instances cell wall-related genes respond similarly to different pathogens and abiotic stresses, even across the monocot-dicot boundary. We propose that the emerging picture of cell wall remodeling during stress is one that utilizes a common toolkit of cell wall-related genes, multiple modifications to cell wall structure, and a defined set of stress-responsive transcription factors that regulate them.

Keywords: abiotic; biotic; cell walls; gene expression; stress.

Figure 1

Analysis of cell wall-related transcripts following abiotic and biotic stresses in Arabidopsis (A) and barley (B). Transcript abundance was determined through meta-analysis of microarray datasets collected from the Plant Expression Database (PLEXdb; Dash et al., 2012) using the experiments listed in Table 2. Values show the average log(2)-fold induction for representatives of each CAZy gene family present on the Arabidopsis Affymetrix 22K ATH1 genome array and the 22K Barley1 genechip. Hierarchical clustering was performed based on the Pearson correlation coefficients across each dataset and CAZy family. Trends conserved in response to the stresses between Arabidopsis and barley are observed in (C) which shows the average fold induction for each gene family for all abiotic and all biotic stresses in Arabidopsis and barley. Asterisks indicate gene families for which expression is upregulated by both abiotic and biotic stresses in Arabidopsis and barley.

Figure 2

Graphical representation the average log(2)-fold induction for each gene family (presented in Figure 1C), which shows the average abiotic (x axis) and average biotic (y axis) stress response in Arabidopsis (A) and barley (B). CAZy families that are upregulated in response to abiotic stresses, but not biotic stresses are colored red, CAZy families that are upregulated in response to biotic stresses, but not abiotic stresses are colored yellow, and CAZy families that are upregulated in response to both abiotic and biotic stresses are colored orange.

Figure 3

Analysis of GT8 family members following abiotic and biotic stresses in Arabidopsis (A) and barley (B). Transcript abundance was determined through meta-analysis of microarray datasets collected from the Plant Expression Database (PLEXdb; Dash et al., 2012) using the experiments listed in Table 2. Values show the average log(2)-fold induction for representatives of each CAZy gene family present on the Arabidopsis Affymetrix 22K ATH1 genome array and the 22K Barley1 genechip. Hierarchical clustering was performed based on the Pearson correlation coefficients across each dataset and CAZy family. (C) Phylogenetic tree of GT8 family members from Arabidopsis and barley with putative functions assigned for each clade. Red dots highlight barley genes that are upregulated in response to stress (B).

Figure 4

Analysis of GT61 family members following abiotic and biotic stresses in Arabidopsis (A) and barley (B). Transcript abundance was determined through meta-analysis of microarray datasets collected from the Plant Expression Database (PLEXdb; Dash et al., 2012) using the experiments listed in Table 2. Values show the average log(2)-fold induction for representatives of each CAZy gene family present on the Arabidopsis Affymetrix 22K ATH1 genome array and the 22K Barley1 genechip. Hierarchical clustering was performed based on the Pearson correlation coefficients across each dataset and CAZy family. (C) Phylogenetic tree of GT61 family members from Arabidopsis, barley, and rice with putative functions assigned for each clade.