[Show abstract][Hide abstract] ABSTRACT: Nitrate acts as a potent signal to control global gene expression in Arabidopsis. Using an integrative bioinformatics approach we identified TGA1 and TGA4 as putative regulatory factors that mediate nitrate responses in Arabidopsis roots. We showed that both TGA1 and TGA4 mRNAs accumulate strongly after nitrate treatments in roots. Global gene expression analysis revealed 97% of the genes with altered expression in tga1/tga4 double mutant plants respond to nitrate treatments indicating these transcription factors have a specific role in nitrate responses in Arabidopsis root organs. We found TGA1 and TGA4 regulate the expression of nitrate transporter genes NRT2.1 and NRT2.2. Specific binding of TGA1 to its cognate DNA sequence on NRT2.1 and NRT2.2 promoters was confirmed by chromatin immunoprecipitation assays. tga1/tga4 double mutant plants exhibit nitrate-dependent lateral and primary root phenotypes. Lateral root initiation is affected in both tga1/tga4 and nrt1.2/nrt2.2 double mutants suggesting TGA1 and TGA4 regulate lateral root development at least partly via NRT2.1 and NRT2.2. Additional root phenotypes of tga1/tga4 double mutants indicate these transcription factors play an important role in root developmental responses to nitrate. These results identify TGA1 and TGA4 as important regulatory factors of the nitrate response in Arabidopsis roots.This article is protected by copyright. All rights reserved.
The Plant Journal 07/2014; 80(1). DOI:10.1111/tpj.12618 · 5.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nitrogen (N) is the mineral nutrient required in the greatest amount and its availability is a major factor limiting growth and development of plants. As sessile organisms, plants have evolved different strategies to adapt to changes in the availability and distribution of N in soils. These strategies include mechanisms that act at different levels of biological organization from the molecular to the ecosystem level. At the molecular level, plants can adjust their capacity to acquire different forms of N in a range of concentrations by modulating the expression and function of genes in different N uptake systems. Modulation of plant growth and development, most notably changes in the root system architecture, can also greatly impact plant N acquisition in the soil. At the organism and ecosystem levels, plants establish associations with diverse microorganisms to ensure adequate nutrition and N supply. These different adaptive mechanisms have been traditionally discussed separately in the literature. To understand plant N nutrition in the environment, an integrated view of all pathways contributing to plant N acquisition is required. Towards this goal, in this review the different mechanisms that plants utilize to maintain an adequate N supply are summarized and integrated.