GH3-mediated auxin homeostasis links growth regulation with stress adaptation response in Arabidopsis
ABSTRACT Plants constantly monitor environmental fluctuations to optimize their growth and metabolism. One example is adaptive growth occurring in response to biotic and abiotic stresses. Here, we demonstrate that GH3-mediated auxin homeostasis is an essential constituent of the complex network of auxin actions that regulates stress adaptation responses in Arabidopsis. Endogenous auxin pool is regulated, at least in part, through negative feedback by a group of auxin-inducible GH3 genes encoding auxin-conjugating enzymes. An Arabidopsis mutant, wes1-D, in which a GH3 gene WES1 is activated by nearby insertion of the (35)S enhancer, exhibited auxin-deficient traits, including reduced growth and altered leaf shape. Interestingly, WES1 is also induced by various stress conditions as well as by salicylic acid and abscisic acid. Accordingly, wes1-D was resistant to both biotic and abiotic stresses, and stress-responsive genes, such as pathogenesis-related genes and CBF genes, were upregulated in this mutant. In contrast, a T-DNA insertional mutant showed reduced stress resistance. We therefore propose that GH3-mediated growth suppression directs reallocation of metabolic resources to resistance establishment and represents the fitness costs of induced resistance.
SourceAvailable from: Pieter Clauw[Show abstract] [Hide abstract]
ABSTRACT: Although the response of plants exposed to severe drought stress has been studied extensively, little is known about how plants adapt their growth under mild drought stress conditions. Here, we analyzed the leaf and rosette growth response of six Arabidopsis thaliana accessions originating from different geographic regions, when exposed to mild drought stress. The automated phenotyping platform WIWAM was used to impose stress early during leaf development, when the third leaf emerges from the shoot apical meristem. Analysis of growth related phenotypes showed differences in leaf development between the accessions. In all six accessions, mild drought stress reduced both leaf pavement cell area and number, without affecting the stomatal index. Genome-wide transcriptome analysis (using RNA sequencing) of early developing leaf tissue identified 354 genes differentially expressed under mild drought stress in the six accessions. Our results indicate the existence of a robust response over different genetic backgrounds to mild drought stress in developing leaves. The processes involved in the overall mild drought stress response comprised abscisic acid signaling, proline metabolism and cell wall adjustments. In addition to these known severe drought related responses, 87 genes were found to be specific for the response of young developing leaves to mild drought stress. Copyright © 2015, American Society of Plant Biologists.Plant physiology 01/2015; 167(3). DOI:10.1104/pp.114.254284 · 7.39 Impact Factor
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ABSTRACT: Growth hormone auxin regulates various cellular processes by altering the expression of diverse genes in plants. Among various auxin-responsive genes, GH3 genes maintain endogenous auxin homeostasis by conjugating excess of auxin with amino acids. GH3 genes have been characterized in many plant species, but not in legumes. In the present work, we identified members of GH3 gene family and analyzed their chromosomal distribution, gene structure, gene duplication and phylogenetic analysis in different legumes, including chickpea, soybean, Medicago, and Lotus. A comprehensive expression analysis in different vegetative and reproductive tissues/stages revealed that many of GH3 genes were expressed in a tissue-specific manner. Notably, chickpea CaGH3-3, soybean GmGH3-8 and -25, and Lotus LjGH3-4, -5, -9 and -18 genes were up-regulated in root, indicating their putative role in root development. In addition, chickpea CaGH3-1 and -7, and Medicago MtGH3-7, -8, and -9 were found to be highly induced under drought and/or salt stresses, suggesting their role in abiotic stress responses. We also observed the examples of differential expression pattern of duplicated GH3 genes in soybean, indicating their functional diversification. Furthermore, analyses of three-dimensional structures, active site residues and ligand preferences provided molecular insights into function of GH3 genes in legumes. The analysis presented here would help in investigation of precise function of GH3 genes in legumes during development and stress conditions.Frontiers in Plant Science 01/2014; 5:789. DOI:10.3389/fpls.2014.00789 · 3.64 Impact Factor
Article: Auxins in defense strategies[Show abstract] [Hide abstract]
ABSTRACT: Plant hormones operate in a very complex network where they regulate and control different vital mechanisms. They coordinate growth, development and defense via signaling involving different interactions of molecules. Activation of molecules responsible for regulation of plant immunity is mainly provided by salicylic and jasmonic acid signaling pathways. Similar to the signaling of these defense-associated plant hormones, auxin can also affect resistance to different pathogen groups and disease is manifested indirectly through the effects on growth. The various ways in which auxin regulate growth and plant development and might be closely connected to plant defense, are discussed in this review.Biologia 10/2014; 69(10). DOI:10.2478/s11756-014-0431-3 · 0.70 Impact Factor