Do PFIs elicit plant cell wall remodelling?
A common feature among the transcript profiling studies was the identification of genes encoding proteins that alter cell wall structure. Genes encoding cell wall-modifying enzymes such as xyloglucan endotransglycosylase (XTH) and pectin methyl esterases were typically up-regulated in infested plants (Moran et al., 2002; Heidel and Baldwin, 2004; Voelckel et al., 2004; Divol et al., 2005; Qubbaj et al., 2005). XTH modifies hemicelluloses by removing and re-attaching oligosaccharides to strengthen cell walls, while pectin esterases can also contribute to cell wall stiffening by controlling both the assembly and disassembly of the pectin network (Willats et al., 2001). Divol et al. (2005) also found strong systemic up-regulation of genes encoding cellulose synthase and expansin in celery petiole phloem in response to green peach aphid feeding on the leaves. Modification of the cell wall structure could play a role in aphid resistance in plants. Genes encoding pectin methyl esterase and i
