Phased Control of Expansin Activity during Leaf Development Identifies a Sensitivity Window for Expansin-Mediated Induction of Leaf Growth  

Abstract

Expansins are cell wall proteins associated with the process of plant growth. However, investigations in which expansin gene expression has been manipulated throughout the plant have often led to inconclusive results. In this article, we report on a series of experiments in which overexpression of expansin was targeted to specific phases of leaf growth using an inducible promoter system. The data indicate that there is a restricted window of sensitivity when increased expansin gene expression leads to increased endogenous expansin activity and an increase in leaf growth. This phase of maximum expansin efficacy corresponds to the mid phase of leaf growth. We propose that the effectiveness of expansin action depends on the presence of other modulating factors in the leaf and we suggest that it is the control of expression of these factors (in conjunction with expansin gene expression) that defines the extent of leaf growth. These data help to explain some of the previously observed variation in growth response following manipulation of expansin gene expression and highlight a potential linkage of the expression of modifiers of expansin activity with the process of exit from cell division.

Combined Large-Scale Phenotyping and Transcriptomics in Maize Reveals a Robust Growth Regulatory Network

“…7), although up-and down-regulation of expansin expression in Arabidopsis and rice resulted in larger and smaller leaves, respectively (Cho and Cosgrove, 2000;Choi et al, 2003;Goh et al, 2012). However, more pleiotropic phenotypes were observed after constitutive modification of expansin gene expression, including a reduction in overall plant growth (Rochange and McQueen-Mason, 2000), demonstrating that the effect of expansin expression on leaf growth is context dependent and influenced by the growth phase of the leaf (Sloan et al, 2009).…”

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

“…4B). The difference between Arabidopsis and native tobacco is most probably related to the fact that leaves used in our experiments have already entered the mid growth phase of development, and their growth therefore mainly depended on expansion of the cells (Sloan et al, 2009) that was then affected by W+OS treatments.…”

“…The growth of the treated leaves was compared with the growth of untreated control leaves of the same developmental stage. Previously, leaf width, a nondestructive parameter of leaf growth, and leaf area, which normally requires destructive leaf removal, have been shown to strongly correlate in tobacco plants (Sloan et al, 2009). To obtain leaf growth kinetics, therefore, we first measured leaf width and leaf length after repeated OS elicitations.…”

Solutions for a local equation of anisotropic plant cell growth: an analytical study of expansin activity

“…Expansins are a superfamily of plant proteins involved in cell wall extension and stress relaxation, abscission, fruit softening, the response to biotic and abiotic stresses, and development of leaf, floral organ, root hairs and grain size [8,9,[17][18][19][20][21][22][23][24][25][26][27][28]. Expansins are subdivided into four families: a-expansin, b-expansin, expansin-like A and expansin-like B [29].…”