Environmentally Induced Plasticity of Root Hair Development in Arabidopsis

Abstract

Postembryonic development of plants is dependent on both intrinsic genetic programs and environmental factors. The plasticity of root hair patterning in response to environmental signals was investigated in the Columbia-0 wild type and 19 Arabidopsis mutants carrying lesions in various parts of the root hair developmental pathway by withholding phosphate or iron (Fe) from the nutrient medium. In the aging primary root and in laterals of the wild type, the number of root hairs increased in response to phosphate and Fe deficiency in a manner typical of each growth type. Although an increase in root hair density in -phosphorus plants was mainly achieved by the formation of extra hairs over both tangential and radial wall of underlying cortical cells, roots of -Fe plants were characterized by a high percentage of extra hairs with two tips. Root hair patterning and hair length was differentially affected by the presence or absence of phosphate and Fe among the genotypes under investigation, pointing to separate cascades of gene activation under all three growth conditions. Divergence in root hair patterning was most pronounced among mutants with defects in genes that affect the first stages of differentiation, suggesting that nutritional signals are perceived at an early stage of epidermal cell development. During elongation of the root hairs, no differences in the requirement of gene products between the growth types were obvious. The role of genes involved in root hair development in the aging primary root of Arabidopsis under the various growth conditions is discussed.

Coexpression-Based Clustering of Arabidopsis Root Genes Predicts Functional Modules in Early Phosphate Deficiency Signaling

“…The gene was down-regulated upon Pi deficiency, consistent with the formation of extra root hairs both in normal and ectopic positions. wer mutants show an exaggerated response to Pi deficiency and form hairs in almost all epidermal cells (Mü ller and Schmidt, 2004). The increase in root hair number in the wer mutant under Pi-deficient conditions is due to an increase of root hairs in ectopic position, which is consistent with the assumption that decreased WER protein is the cause of an increased number of epidermal cells entering the root hair cell fate upon Pi deficiency.…”

“…Root hair morphology is substantially altered by Pi starvation, mainly by inducing extra root hairs that are markedly longer than those formed under control conditions (Mü ller and Schmidt, 2004). In addition, root hairs of Pi-deficient plants are denser, due to decreased longitudinal elongation of epidermal cells and to the development of root hairs in positions normally occupied by nonhair cells.…”

“…These global processes include changes in membrane lipid composition (Kobayashi et al, 2006), secretion of phosphatases (Bozzo et al, 2002), and expression of Pi transporters (Poirier and Bucher, 2002;Guo et al, 2008;Cubero et al, 2009). In addition, the acquisition of Pi is facilitated by alterations in root architecture and by the formation of root hairs with increased length and density (Bates and Lynch, 1996;Ma et al, 2001;Williamson et al, 2001;Mü ller and Schmidt, 2004). The latter trait is of particular importance when depletion zones, caused by the low mobility of Pi via mass flow and diffusion, develop around the root surface (Ma et al, 2001).…”

Invasion of Lotus japonicus root hairless 1 by Mesorhizobium loti Involves the Nodulation Factor-Dependent Induction of Root Hairs

“…For root hair length measurements, the agar plate condition were used as described for Arabidopsis (Arabidopsis thaliana; Muller and Schmidt, 2004), except that the subsequent incubation was as in Wopereis et al (2000). Unstained root images of 5-d-old plants were captured with a DMX1200 digital camera (Nikon, Tokyo) connected to a SMZ 1500 microscope (Nikon) and root hair lengths were measured manually, using a standard ruler, directly from enlarged printed images.…”

Natural Variation of Root Traits: From Development to Nutrient Uptake

“…The best characterized response is an increase in surface area by the formation of ectopic root hairs (Schmidt et al, 2000) and the development of hairs with bifurcated tips (two tips; Müller and Schmidt, 2004;Perry et al, 2007). Root growth rates are affected by iron deficiency as well, and whereas mild iron deficiency causes increased PR length, severe deficiency causes a strong reduction of PR and LR lengths (Gruber et al, 2013).…”