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Expression data from overexpressers and mutants of TFs-gene LBD37 and LBD38 under different nitrogen regimes

ABSTRACT: Nitrogen (N) and nitrate (NO3-) per se regulate many aspects of plant metabolism, growth and development. N/NO3- also suppresses parts of secondary metabolism including anthocyanin synthesis. Molecular components for this repression are unknown. We report that three N/NO3--induced members of the LATERAL ORGAN BOUNDARY DOMAIN (LBD) gene family of transcription factors (LBD37, LBD38 and LBD39) act as negative regulators of anthocyanin biosynthesis in Arabidopsis (Arabidopsis thaliana). Over-expression of each of the three genes in the absence of N/NO3- strongly suppresses the key regulators of anthocyanin synthesis PAP1 and PAP2, genes in the anthocyanin-specific part of flavonoid synthesis, as well as cyanidin- but not quercetin- or kaempferol-glycoside production. Conversely, lbd37, lbd38 or lbd39 T-DNA insertion mutants accumulate anthocyanins when grown in N/NO3--sufficient conditions and show constitutive expression of anthocyanin biosynthetic genes. The LBD genes also repress many other known N-responsive genes including key genes required for NO3- uptake and assimilation, resulting in altered NO3- content, nitrate reductase activity/activation, protein, amino acid and starch levels, and N-related growth phenotypes. The results identify LBD37 and its two close homologs as novel repressers of anthocyanin biosynthesis and N-availability signals in general. They also show that besides being developmental regulators LBD genes fulfill roles in metabolic regulation. We used microarrays to test whether LBD37 and LBD38 have a more widespread role in NO3-/N-regulation.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE18818 | GEO | 2009/11/24

SECONDARY ACCESSION(S): PRJNA121681

REPOSITORIES: GEO

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Project description:Arable soils are extremely heterogeneous in spatial nutrient distribution. It is well documented that lateral roots (LRs) proliferate in nitrate-rich patch. Yet less information is available as to which genes are involved in this process, in particular in cereals. To understand the molecular mechanism for local nitrate induced LR growth in maize (Zea mays L.), we analyzed the gene expression profiling in maize root in early response (1 hour) to local nitrate stimulation by using Maize Oligonucleotide Array (http://www.maizearray.org) and a split-root system. Selected differentially expressed genes were further confirmed by semi-quantitative RT-PCR. The results showed that reception and/or transduction of local NO3- signal involve some important protein kinases and protein phosphatases (histidine kinases, serine/threonine kinases, protein phosphatase 2A etc.) and transcription factors (F-box, Zinc finger, Myb and bZIP transcription factors and response regulator). Increasing expression of genes encoding auxin response factor 7b, ethylene receptor, and cytokinin oxidase suggests strong interaction among hormonal pathways and local NO3- signaling pathways. Genes involving NO3- uptake and assimilation (NRT2.1, NR, etc.), sugar transport (a sugar transporter) and utilization (a sucrose synthase) were enhanced in the N-fed root. Furthermore, local NO3- induces rapid expression of genes related to cell division and expansion such as alpha-expansin, celluose synthase, kinesin, plasma membrane and tonoplast aquaporins. Based on the differentially expressed genes, a putative model which combines both the 'NO3- signal' and 'metabolic sink' theories is proposed to explain the molecular mechanism controlling local nitrate induced LR elongation in maize. plants were pre-cultured in solution containing 0.5 mmol L-1 NO3- for 6 days and then transferred to N-free solution to grow for another 2 days. Then these plants were transferred to a two-compartment split-root system with only half root supplied with 1.0 mmol L-1 NO3-. Supply of Ca2+ in the N-free half was compensated by adding 1.0 mmol L-1 CaCl2. One hour after the local nitrate treatment, root segments (15cm from root tip to lateral root elongation zone) were sampled for RNA extraction. Two biological replicates were performed for each treatment.

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Expression data from overexpressers and mutants of TFs-gene LBD37 and LBD38 under different nitrogen regimes

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