Expansins

Cuticular plasticization in the tick,Amblyomma hebraeum(Acari: Ixodidae): possible roles of monoamines and cuticular pH

“…Similar to what occurs in R. prolixus (Reynolds, 1975b), the tick H. longicornis (Okura et al, 1997a) and now A. hebraeum, growing plant cells stretch little when placed under load following exposure to media of neutral or alkaline pH but at acidic pH, they expand much more rapidly under the same load (Rayle et al, 1970). The mechanism of this acidinduced 'plasticization' is probably the disruption of hydrogen bonds '… between cellulose microfibrils and the hemicellulose polymers that coat them in the cell wall' (McQueen-Mason et al, 2006).…”

“…For example, in plants, cellulose serves both as a rigid skeletal support and as the means to withstand the particularly high turgor pressures generated within the plant cell: typically in the region of 0.5MPa but up to 50MPa in stomatal guard cells (McQueen-Mason et al, 2006). Expansins are a family of plant proteins that facilitate growth by means of a process of acid-induced cell wall extension (reviewed by McQueen-Mason et al, 2006).…”

“…For example, in plants, cellulose serves both as a rigid skeletal support and as the means to withstand the particularly high turgor pressures generated within the plant cell: typically in the region of 0.5MPa but up to 50MPa in stomatal guard cells (McQueen-Mason et al, 2006). Expansins are a family of plant proteins that facilitate growth by means of a process of acid-induced cell wall extension (reviewed by McQueen-Mason et al, 2006). Similar to what occurs in R. prolixus (Reynolds, 1975b), the tick H. longicornis (Okura et al, 1997a) and now A. hebraeum, growing plant cells stretch little when placed under load following exposure to media of neutral or alkaline pH but at acidic pH, they expand much more rapidly under the same load (Rayle et al, 1970).…”

The Microtubule Plus-End Binding Protein EB1 Functions in Root Responses to Touch and Gravity Signals in Arabidopsis

“…In roots that have been reoriented into a horizontal plane, cell elongation increases on the upper flank and decreases on the lower flank, causing the root to bend down (Mullen et al, 1998a). Changes in elongation rates are thought to be effected via alterations in the extensibility of the cell wall (McQueen-Mason et al, 2007). The fact that eb1 roots exhibit extended horizontal growth before they initiate a bend suggests that there are delays in triggering changes in elongation rates across the root.…”

Arabidopsis TCH4, Regulated by Hormones and the Environment, Encodes a Xyloglucan Endotransglycosylase

“…Furthermore, protein extracts rich in XET activity are incapable of eliciting extension in isolated cucumber hypocotyl segments (McQueen-Mason et al, 1993). Other proteins, called expansins, have been identified recently that are sufficient to cause extension in this in vitro extension assay (McQueen-Mason et al, 1992), yet these proteins lack XET activity (McQueen-Mason et al, 1993). Thus, other proteins unrelated to XETs likely play critical roles in plant cell expansion and growth.…”