Regulation of Root Development by Glutamate Receptor-Like gene GLR3.6 and Glutamate in Arabidopsis thaliana
Date Issued
2016
Date
2016
Author(s)
Singh, Shashi Kant
Abstract
Arabidopsis putative glutamate receptor (AtGLR)-like genes seem important regulators participating in the plant growth and development processes, and the functions of the most of them remain unknown. AtGLR3.6 is one of the 20 AtGLR-like genes in Arabidopsis and belongs to clade-III. Here we have investigated the role of AtGLR3.6 in root development in Arabidopsis thaliana. Our results revealed that AtGLR3.6 gene was expressed in roots as well as shoots. Moreover, AtGLR3.6 protein was observed in the plasma membrane. Furthermore, the loss-of-function of AtGLR3.6 (glr3.6-1) leads to reduced primary root growth and fewer lateral roots. The over-expression of AtGLR3.6 significantly promoted lateral and primary root and shoot growth in Arabidopsis. The glr3.6-1 mutant exhibited a smaller root meristem size compared with that of the wild-type, indicating that AtGLR3.6 controls root meristem size. In addition, atglr3.6-1 roots show a decreased mitotic activity accounting for reduced root meristem size. The expression of the cyclin-dependent kinase inhibitor Kip-related protein 4 (KRP4) gene was significantly upregulated in the mutant and downregulated in AtGLR3.6-overexpressing roots, suggesting a role of KRP4 in AtGLR3.6-mediated root meristem maintenance. The upregulation of KRP4 in transgenic Arabidopsis exhibited significantly reduced shoot and root growth with reduced root meristem size. Importantly, glr3.6-1 mutant recovered most of its root growth when KRP4 expression was downregulated. However, elevated KRP4 expression in AtGLR3.6-overexpressing plants phenocopied the wild-type root growth. The magnitude of [Ca2+]cyt elevation was reduced in glr3.6-1 mutant roots. Moreover, calcium treatment reduced KRP4 mRNA level, thereby inducing root growth. To further confirm the role of putative glutamate (glu) signaling, we used a set of compounds that have the ability to modulate the activity of animal iGluRs . We used Glu and other compounds known to agonize or antagonize the animal iGluR channels. iGluR receptor agonists and antagonists altered root development in Arabidopsis. Our results demonstrate that the root growth was promoted by animal iGluR agonists and then was drastically reduced by animal iGluR antagonists. Recovery of root architectures by the addition of Glu in antagonist-treated root is highly related to each other. Taken together, our findings suggest that AtGLR3.6 is a positive regulator that controls lateral and primary root development in Arabidopsis
Subjects
glutamate receptor
lateral root
auxin
calcium
Type
thesis
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