Project description:Auxin is a key phytohormone regulating central processes in plants that include embryo development, lateral root growth and flower maturation among others. Auxin is sensed by a set of F-Box proteins of the TIR1/AFB3 family triggering auxin dependent responses by a pathway that involves an interplay between the Aux/IAA transcription repressors and the ARF transcription factors. We have previously shown that the AFB3 auxin receptor has a specific role in coordinating primary and lateral root growth to external and internal nitrate availability (Vidal et al., 2010). In this work, we used an integrated genomics, bioinformatics and molecular genetics approach to dissect regulatory networks acting downstream AFB3 that are activated by a transient nitrate treatment in Arabidopsis roots. Our systems approach unraveled key components of the AFB3 regulatory network leading to changes in lateral root growth in response to nitrate. Arabidopsis seedlings of the Ws and afb3-1 genotypes were grown on hydroponic medium containing 1X MS salts without Nitrogen, supplemented with 0.5 mM ammonium succinate as Nitrogen source and 3 mM sucrose on a Percival chamber under a photoperiod of 16 hours of light (100 μE/m2/sec) and 8 hours of dark at 22°C for 14 days. The plants were treated at the onset of the light cycle with 5 mM KNO3 or 5 mM KCl as control for 2 hours. Whole roots were cut from seedlings and frozen on liquid Nitrogen. Total RNA was extracted using the TriZol reagent. 3 independent biological replicates were performed.
Project description:Plants modulate the efficiency of root nitrogen (N) acquisition in response to shoot N demand. However, molecular components directly involved in this shoot-to-root communication remain to be identified. Here, we show that phloem-mobile CEPD-like 2 (CEPDL2) polypeptide is upregulated in the leaf vasculature in response to decreased shoot N status and, after translocation to the roots, promotes high-affinity uptake and root-to-shoot transport of nitrate by activating nitrate transporter genes such as NRT2.1, NRT3.1 and NRT1.5. Loss of CEPDL2 decreases nitrate uptake and root-to-shoot transport activity in roots, leading to a reduction in shoot nitrate content and plant biomass. CEPDL2 contributes to N acquisition cooperatively with CEPD1 and CEPD2 that mediate root N status, and their complete loss severely impairs N homeostasis in plants. Reciprocal grafting analysis provided conclusive evidence that the shoot CEPDL2/CEPD genotype defines the root high-affinity uptake activity of nitrate. Our results indicate that plants integrate shoot N status and root N status in leaves and systemically regulate the efficiency of root N acquisition.
Project description:gnp3-b4_nitrogen_starvation - nitrogen starvation and re-supply - What are the transcriptomic short- and long-term plant responses to nitrogen starvation and nitrogen re-supply? - WS Arabidopsis ecotype were grown on 6mM nitrate as sole nitrogen source during 35 days under short days . At T0, plants were then starved for nitrate for 10 days and root and shoot samples were harvested separately 2 and 10 days after treatment (T2, T10). Then, nitrate (6 mM) was re-supplied for 1 and 24 hours (T+1, T+24). Keywords: time course
Project description:af47_thioredoxins - comparison ws vs de and dy - Knock-out mutants of the ferredoxin-thioredoxin reductase were used to evaluate the impact of the redox perturbation of the plastidial thioredoxins on Arabidopsis transcriptome. - Wild-type (WS) and two T-DNA mutant lines for the variable subunit of ferredoxin:thioredoxin reductase ( DY and DE from INRA of Versailles collection) were compared Keywords: wt vs mutant comparison
Project description:Transcriptional profiling of arsenic-induced toxicity and tolerance in Arabidopsis plants of different ecotypes Arsenic (As) is a toxic metalloid found ubiquitously in the environment and has widely been known as an acute poison and carcinogen. As toxicity is a major factor leading to root growth inhibition in plants. However, the molecular mechanisms of plants in response to As has not been extensively characterized. In this study, Arabidopsis ecotypes that are As-tolerant (Col-0) and -sensitive (Ws-2) were used to conduct a transcriptome analysis of the response to As (V). To begin elucidating the molecular basis of As toxicity and tolerance in Arabidopsis, seedlings of Col-0 and Ws-2 were subjected to As treatment. The root elongation rate of Col-0 was significantly higher than that of Ws-2 when exposed to As. The tolerant ecotype (Col-0) demonstrated lower accumulation of As when compared to the responses observed in the sensitive Ws-2. Subsequently, the effect of As exposure on genome-wide gene expression was examined in the two ecotypes. Comparative analysis of microarray data identified groups of genes with common and specific responses to As between Col-0 and Ws-2. The genes related to heat responses and oxidative stresses belonged to common responses, indicating conserved stress-associated changes across two ecotypes. The majority of specific responsive genes were those encoding heat shock proteins, heat shock factors, ubiquitin and transporters. The data suggested that metal transport and maintenance of protein structure may be important mechanisms for toxicity and tolerance to As. This study presents comprehensive surveys of global transcriptional regulation and identifies stress- and tolerance-associated genes in response to As.
Project description:Background: Skewing root patterns provide key insights into root growth strategies and mechanism that produce root architectures Roots exhibit skewing and waving when grown on a tilted, impenetrable surface, and while the genetics guiding these morphologies have been examined, the underlying molecular mechanisms of skewing and waving remain unclear. In this study, transcriptome data were derived from two Arabidopsis ecotypes, WS and Col-0, under three tilted growth conditions in order to identify candidate genes involved in skewing. WS is a skewing ecotype. Col-0 is a non-skewing ecotype. Results: This work identifies a number of genes that are likely involved in skewing, using growth conditions that differentially affect skewing and waving. Comparing the gene expression profiles of WS and Col-0 in different tilted growth conditions identified 11 candidate genes as potentially involved in the control of skewing. These 11 genes are involved in several different cellular processes, including sugar transport, salt signaling, cell wall organization, and hormone signaling. Conclusions: Many of the 11 identified genes are involved in signaling and perception, rather than the physical restructuring of roots, leading to the conclusion that root skewing is enabled through diverse environmental signaling pathways. These findings revealed further insights into the molecular mechanisms behind root skewing. This work investigated the transcriptional differences between skewing and non-skewing roots. Comparisons within WS revealed gees that that responded to the angle of growth (Agp) during the process of skewing. These genes were cross referenced with transcripts differing between the WS and Col-0 genotypes to refine the list of genes that are most probably be involved in root skewing. More of the highly probable skew gene candidates (HPSGC) are associated with environmental sensing (e.g. salt, sugar, hormones, darkness) than with physical growth differences (e.g. cell wall remodeling, cell division, cell elongation). Thus, the root behavior of skewing appears to be primarily driven by pathways that respond to disparate signals from the root local environment. Future studies could investigate the HPSGC to find the specific pathways and molecular mechanisms contributing to root skewing.