Plants as a realized niche for Listeria monocytogenes.

Listeria monocytogenes is a human pathogen. It is the causative agent of listeriosis, the leading cause of bacterial-linked foodborne mortality in Europe and elsewhere. Outbreaks of listeriosis have been associated with the consumption of fresh produce including vegetables and fruits.

Nitrogen modulation of Medicago truncatula resistance to Aphanomyces euteiches depends on plant genotype.

Nitrogen (N) availability can impact plant resistance to pathogens by the regulation of plant immunity. To better understand the links between N nutrition and plant defence, we analysed the impact of N availability on Medicago truncatula resistance to the root pathogen Aphanomyces euteiches. This oomycete is considered to be the most limiting factor for legume production.

A new NO ledge in Chlamydomonas: when the old nitrate reductase meets amidoxime reducing component to produce nitric oxide.

This article comments on: A dual system formed by the ARC and NR molybdoenzymes mediates nitrite-dependent NO production in Chlamydomonas.

RhizoTubes as a new tool for high throughput imaging of plant root development and architecture: test, comparison with pot grown plants and validation.

Background: In order to maintain high yields while saving water and preserving non-renewable resources and thus limiting the use of chemical fertilizer, it is crucial to select plants with more efficient root systems. This could be achieved through an optimization of both root architecture and root uptake ability and/or through the improvement of positive plant interactions with microorganisms in the rhizosphere. The development of devices suitable for high-throughput phenotyping of root structures remains a major bottleneck.

Cross-Regulation between N Metabolism and Nitric Oxide (NO) Signaling during Plant Immunity.

Plants are sessile organisms that have evolved a complex immune system which helps them cope with pathogen attacks. However, the capacity of a plant to mobilize different defense responses is strongly affected by its physiological status. Nitrogen (N) is a major nutrient that can play an important role in plant immunity by increasing or decreasing plant resistance to pathogens.

The Medicago truncatula hypermycorrhizal B9 mutant displays an altered response to phosphate and is more susceptible to Aphanomyces euteiches.

Inorganic phosphate (Pi) plays a key role in the development of arbuscular mycorrhizal (AM) symbiosis, which is favoured when Pi is limiting in the environment. We have characterized the Medicago truncatula hypermycorrhizal B9 mutant for its response to limiting (P/10) and replete (P2) Pi. On P2, mycorrhization was significantly higher in B9 plants than in wild-type (WT).

Combined phosphate and nitrogen limitation generates a nutrient stress transcriptome favorable for arbuscular mycorrhizal symbiosis in Medicago truncatula.

Arbuscular mycorrhizal (AM) symbiosis is stimulated by phosphorus (P) limitation and contributes to P and nitrogen (N) acquisition. However, the effects of combined P and N limitation on AM formation are largely unknown. Medicago truncatula plants were cultivated in the presence or absence of Rhizophagus irregularis (formerly Glomus intraradices) in P-limited (LP), N-limited (LN) or combined P- and N-limited (LPN) conditions, and compared with plants grown in sufficient P and N.

The Arabidopsis abscisic acid catabolic gene CYP707A2 plays a key role in nitrate control of seed dormancy.

Nitrate releases seed dormancy in Arabidopsis (Arabidopsis thaliana) Columbia accession seeds in part by reducing abscisic acid (ABA) levels. Nitrate led to lower levels of ABA in imbibed seeds when included in the germination medium (exogenous nitrate). Nitrate also reduced ABA levels in dry seeds when provided to the mother plant during seed development (endogenous nitrate).

The Arabidopsis ATNRT2.7 nitrate transporter controls nitrate content in seeds.

In higher plants, nitrate is taken up by root cells where Arabidopsis thaliana NITRATE TRANSPORTER2.1 (ATNRT2.1) chiefly acts as the high-affinity nitrate uptake system.

Homogalacturonan synthesis in Arabidopsis thaliana requires a Golgi-localized protein with a putative methyltransferase domain.

Pectins are a family of complex cell-wall polysaccharides, the biosynthesis of which remains poorly understood. We identified dwarf mutants with reduced cell adhesion at a novel locus, QUASIMODO2 (QUA2). qua2-1 showed a 50% reduction in homogalacturonan (HG) content compared with the wild type, without affecting other cell-wall polysaccharides.

QUASIMODO1 is expressed in vascular tissue of Arabidopsis thaliana inflorescence stems, and affects homogalacturonan and xylan biosynthesis.

An insertion in the promoter of the Arabidopsis thaliana QUA1 gene (qua1-1 allele) leads to a dwarf plant phenotype and a reduction in cell adhesion, particularly between epidermal cells in seedlings and young leaves. This coincides with a reduction in the level of homogalacturonan epitopes and the amount of GalA in isolated cell walls (Bouton et al., Plant Cell 14: 2577 2002).

An Arabidopsis homolog of RAPTOR/KOG1 is essential for early embryo development.

The RAPTOR/KOG1 proteins are binding partners of the target of rapamycin (TOR) kinase that is present in all eucaryotes and plays a central role in the stimulation of cell growth and metabolism in response to nutrients. We show in this report that two genes are coding for RAPTOR/KOG1 homologs in the Arabidopsis and rice genomes. Disruption of the Arabidopsis AtRaptor1 gene leads to a very early arrest of embryo development whereas disruption of the AtRaptor2 gene, which is expressed at a lower level than AtRaptor1, has no visible effects on embryo and plant development.