Expansins and coleoptile elongation in wheat

Abstract

Expansins are now generally accepted to be the key regulators of wall extension during plant growth. The aim of this study was to characterize expansins in wheat coleoptiles and determine their roles in regulating cell growth. Endogenous and reconstituted wall extension activities of wheat coleoptiles were measured. The identification of beta-expansins was confirmed on the basis of expansin activity, immunoblot analysis, and beta-expansin inhibition. Expansin activities of wheat coleoptiles were shown to be sensitive to pH and a number of exogenously applied factors, and their optimum pH range was found to be 4.0 to 4.5, close to that of alpha-expansins. They were induced by dithiothreitol, K(+), and Mg(2+), but inhibited by Zn(2+), Cu(2+), Al(3+), and Ca(2+), similar to those found in cucumber hypocotyls. An expansin antibody raised against TaEXPB23, a vegetative expansin of the beta-expansin family, greatly inhibited acid-induced extension of native wheat coleoptiles and only one protein band was recognized in Western blot experiments, suggesting that beta-expansins are the main members affecting cell wall extension of wheat coleoptiles. The growth of wheat coleoptiles was closely related to the activity and expression of expansins. In conclusion, our results suggest the presence of expansins in wheat coleoptiles, and it is possible that most of them are members of the beta-expansin family, but are not group 1 grass pollen allergens. The growth of wheat coleoptiles is intimately correlated with expansin expression, in particularly that of beta-expansins.

Recombinant DNA modification of gibberellin metabolism alters growth rate and biomass allocation in Populus

“…In maize, where EXPBs were firstly identified as group-1 grass pollen allergens, some EXPBs (e.g., Zeam1) are known to play a role in pollen tube penetration (Cosgrove et al 1997), while others (e.g., ZmEXPB2) appear to take part in root elongation (Kam et al 2005). Root-specific/preferred EXPBs have also been isolated from barley (HvEXPB1), wheat (TaEXPB23), rice (OsEXPB5), Arabidopsis (AtEXPB1), and soybean (GmEXPB1, GmEXPB2, and GmEXPB6) (Kwasniewski and Szarejko 2006;Gao et al 2008;Kwon et al 2008;Won et al 2010;Li et al 2011Li et al , 2013. The root-specific activity of HvEXPB1 from barley and OsEXPB5 from rice has been shown to be conferred by root hair specific cis-elements (RHEs) (Won et al 2010).…”

Expansins are involved in cell growth mediated by abscisic acid and indole-3-acetic acid under drought stress in wheat

“…In a resurrection plant, Craterostigma plantagineum, the increase in expansin activity was accompanied by the enhancement of wall extensibility during dehydration and rehydration processes, suggesting a role of expansin proteins in increasing wall flexibility and promoting leaf growth under drought stress (Jones and McQueen-Mason 2004). In our previous report, drought stress was shown to induce the expression and activity of expansin protein in wheat coleoptiles (Gao et al 2008;Zhao et al 2011). Over-expression of an expansin gene TaEXPB23 from wheat enhanced the drought tolerance in transgenic tobacco (Li et al 2010).…”

“…To measure endogenous expansin activity, acid-induced cell wall extension was performed according to the methods described by Cosgrove (1989) and Gao et al (2008). Coleoptiles were abraded with carborundum and squeezed between two glass slides to remove cell sap.…”

“…The extraction of the cell wall proteins were performed according to Gao et al (2008) based on McQueen-Mason et al (1992). Plant materials were homogenized in a blender in cold buffer [20 mM sodium acetate, pH 4.5, 2 mM disodium ethylenediaminetetra acetate (EDTA)].…”

Jasmonic Acid and Ethylene Modulate Local Responses to Wounding and Simulated Herbivory inNicotiana attenuataLeaves

“…Three up-regulated genes putatively associated with cell wall expansion in mETR1asLOX3 leaves were further analyzed by quantitative real-time (qRT)-PCR using leaf samples collected at 0, 6, 20, and 60 h after W+OS treatment. Pectin methylesterase (+2.7-fold change; BP131988) and expansin (+1.9-fold change; BP531140), previously shown to mediate cell expansion in other plant species (Micheli, 2001;Pien et al, 2001;Gao et al, 2008), showed more abundant transcripts in mETR1asLOX3 compared with wildtype and remaining transgenic lines (Fig. 6).…”