Ammonium stress increases microautophagic activity while impairing macroautophagic flux in Arabidopsis roots.

Plant responses to NH stress are complex, and multiple mechanisms underlying NH sensitivity and tolerance in plants may be involved. Here, we demonstrate that macro- and microautophagic activities are oppositely affected in plants grown under NH toxicity conditions. When grown under NH stress conditions, macroautophagic activity was impaired in roots.

Autophagy Increases Zinc Bioavailability to Avoid Light-Mediated Reactive Oxygen Species Production under Zinc Deficiency.

Zinc (Zn) is an essential micronutrient for plant growth. Accordingly, Zn deficiency (-Zn) in agricultural fields is a serious problem, especially in developing regions. Autophagy, a major intracellular degradation system in eukaryotes, plays important roles in nutrient recycling under nitrogen and carbon starvation.

Responses of symbiotic nitrogen-fixing common bean to aluminum toxicity and delineation of nodule responsive microRNAs.

Aluminum (Al) toxicity is widespread in acidic soils where the common bean (Phaseolus vulgaris), the most important legume for human consumption, is produced and it is a limiting factor for crop production and symbiotic nitrogen fixation. We characterized the nodule responses of common bean plants inoculated with Rhizobioum tropici CIAT899 and the root responses of nitrate-fertilized plants exposed to excess Al in low pH, for long or short periods. A 43-50% reduction in nitrogenase activity indicates that Al toxicity (Alt) highly affected nitrogen fixation in common bean.

Assessment and optimization of autophagy monitoring methods in Arabidopsis roots indicate direct fusion of autophagosomes with vacuoles.

Autophagy is a degradation pathway that recycles cell materials upon encountering stress conditions or during specific developmental processes. To better understand the physiological roles of autophagy, proper monitoring methods are very important. In mammals and yeast, monitoring of autophagy is often performed with a green fluorescent protein (GFP)-ATG8 fusion protein or with acidotropic dyes such as monodansylcadaverine (MDC) and LysoTracker Red (LTR).

Regulation of copper homeostasis and biotic interactions by microRNA 398b in common bean.

MicroRNAs are recognized as important post-transcriptional regulators in plants. Information about the roles of miRNAs in common bean (Phaseolus vulgaris L.), an agronomically important legume, is yet scant.

Cleavage of a non-conserved target by a specific miR156 isoform in root apexes of Medicago truncatula.

Micro RNAs (miRNAs) have emerged as an important class of gene expression regulators controlling development, growth and metabolism. These short RNA molecules are 20-24 nucleotides in length and act post-transcriptionally to regulate the cleavage or translation of specific mRNA targets. In the model legume Medicago truncatula, we have recently reported identification of 100 novel and 27 conserved miRNAs in root apexes and nodules.

Genome-wide Medicago truncatula small RNA analysis revealed novel microRNAs and isoforms differentially regulated in roots and nodules.

Posttranscriptional regulation of a variety of mRNAs by small 21- to 24-nucleotide RNAs, notably the microRNAs (miRNAs), is emerging as a novel developmental mechanism. In legumes like the model Medicago truncatula, roots are able to develop a de novo meristem through the symbiotic interaction with nitrogen-fixing rhizobia. We used deep sequencing of small RNAs from root apexes and nodules of M.

The glutathione peroxidase gene family of Lotus japonicus: characterization of genomic clones, expression analyses and immunolocalization in legumes.

Despite the multiple roles played by antioxidants in rhizobia-legume symbioses, little is known about glutathione peroxidases (GPXs) in legumes. Here the characterization of six GPX genes of Lotus japonicus is reported. Expression of GPX genes was analysed by quantitative reverse transcription-polymerase chain reaction in L.

Functional characterization of an unusual phytochelatin synthase, LjPCS3, of Lotus japonicus.

In plants and many other organisms, phytochelatin synthase (PCS) catalyzes the synthesis of phytochelatins from glutathione in the presence of certain metals and metalloids. We have used budding yeast (Saccharomyces cerevisiae) as a heterologous system to characterize two PCS proteins, LjPCS1 and LjPCS3, of the model legume Lotus japonicus. Initial experiments revealed that the metal tolerance of yeast cells in vivo depends on the concentrations of divalent cations in the growth medium.

The response of carbon metabolism and antioxidant defenses of alfalfa nodules to drought stress and to the subsequent recovery of plants.

Alfalfa (Medicago sativa) plants were exposed to drought to examine the involvement of carbon metabolism and oxidative stress in the decline of nitrogenase (N(2)ase) activity. Exposure of plants to a moderate drought (leaf water potential of -1.3 MPa) had no effect on sucrose (Suc) synthase (SS) activity, but caused inhibition of N(2)ase activity (-43%), accumulation of succinate (+36%) and Suc (+58%), and up-regulation of genes encoding cytosolic CuZn-superoxide dismutase (SOD), plastid FeSOD, cytosolic glutathione reductase, and bacterial MnSOD and catalases B and C.

Phytochelatin synthases of the model legume Lotus japonicus. A small multigene family with differential response to cadmium and alternatively spliced variants.

The biosynthesis of phytochelatins and homophytochelatins has been studied in nodulated plants of the model legume Lotus (Lotus japonicus). In the first 6 to 24 h of treatment with cadmium (Cd), roots started to synthesize elevated amounts of both polypeptides, with a concomitant increase of glutathione and a decrease of homoglutathione, indicating the presence of active phytochelatin synthase (PCS) genes. Screening of transformation-competent artificial chromosome libraries allowed identification of a cluster of three genes, LjPCS1, LjPCS2, and LjPCS3, which were mapped at 69.

A reassessment of substrate specificity and activation of phytochelatin synthases from model plants by physiologically relevant metals.

Phytochelatin synthases (PCS) catalyze phytochelatin (PC) synthesis from glutathione (GSH) in the presence of certain metals. The resulting PC-metal complexes are transported into the vacuole, avoiding toxic effects on metabolism. Legumes have the unique capacity to partially or completely replace GSH by homoglutathione (hGSH) and PCs by homophytochelatins (hPCs).