A member of the Whirly family is a multifunctional RNA- and DNA-binding protein that is essential for chloroplast biogenesis

‘Whirly’ proteins comprise a plant-specific protein family whose members have been described as DNA-binding proteins that influence nuclear transcription and telomere maintenance, and that associate with nucleoids in chloroplasts and mitochondria. We identified the maize WHY1 ortholog among proteins that coimmunoprecipitate with CRS1, which promotes the splicing of the chloroplast atpF group II intron. ZmWHY1 localizes to the chloroplast stroma and to the thylakoid membrane, to which it is tethered by DNA. Genome-wide coimmunoprecipitation assays showed that ZmWHY1 in chloroplast extract is associated with DNA from throughout the plastid genome and with a subset of plastid RNAs that includes atpF transcripts. Furthermore, ZmWHY1 binds both RNA and DNA in vitro. A severe ZmWhy1 mutant allele conditions albino seedlings lacking plastid ribosomes; these exhibit the altered plastid RNA profile characteristic of ribosome-less plastids. Hypomorphic ZmWhy1 mutants exhibit reduced atpF intron splicing and a reduced content of plastid ribosomes; aberrant 23S rRNA metabolism in these mutants suggests that a defect in the biogenesis of the large ribosomal subunit underlies the ribosome deficiency. However, these mutants contain near normal levels of chloroplast DNA and RNAs, suggesting that ZmWHY1 is not directly required for either DNA replication or for global plastid transcription

Allele-Specific Virulence Attenuation of the Pseudomonas syringae HopZ1a Type III Effector via the Arabidopsis ZAR1 Resistance Protein

Plant resistance (R) proteins provide a robust surveillance system to defend against potential pathogens. Despite their importance in plant innate immunity, relatively few of the ∼170 R proteins in Arabidopsis have well-characterized resistance specificity. In order to identify the R protein responsible for recognition of the Pseudomonas syringae type III secreted effector (T3SE) HopZ1a, we assembled an Arabidopsis R gene T–DNA Insertion Collection (ARTIC) from publicly available Arabidopsis thaliana insertion lines and screened it for plants lacking HopZ1a-induced immunity. This reverse genetic screen revealed that the Arabidopsis R protein HOPZ-ACTIVATED RESISTANCE 1 (ZAR1; At3g50950) is required for recognition of HopZ1a in Arabidopsis. ZAR1 belongs to the coiled-coil (CC) class of nucleotide binding site and leucine-rich repeat (NBS–LRR) containing R proteins; however, the ZAR1 CC domain phylogenetically clusters in a clade distinct from other related Arabidopsis R proteins. ZAR1–mediated immunity is independent of several genes required by other R protein signaling pathways, including NDR1 and RAR1, suggesting that ZAR1 possesses distinct signaling requirements. The closely-related T3SE protein, HopZ1b, is still recognized by zar1 Arabidopsis plants indicating that Arabidopsis has evolved at least two independent R proteins to recognize the HopZ T3SE family. Also, in Arabidopsis zar1 plants HopZ1a promotes P. syringae growth indicative of an ancestral virulence function for this T3SE prior to the evolution of recognition by the host resistance protein ZAR1. Our results demonstrate that the Arabidopsis resistance protein ZAR1 confers allele-specific recognition and virulence attenuation of the Pseudomonas syringae T3SE protein HopZ1a

Identification of gene modules associated with low temperatures response in Bambara groundnut by network-based analysis

Bambara groundnut (Vigna subterranea (L.) Verdc.) is an African legume and is a promising underutilized crop with good seed nutritional values. Low temperature stress in a number of African countries at night, such as Botswana, can effect the growth and development of bambara groundnut, leading to losses in potential crop yield. Therefore, in this study we developed a computational pipeline to identify and analyze the genes and gene modules associated with low temperature stress responses in bambara groundnut using the cross-species microarray technique (as bambara groundnut has no microarray chip) coupled with network-based analysis. Analyses of the bambara groundnut transcriptome using cross-species gene expression data resulted in the identification of 375 and 659 differentially expressed genes (p<0.01) under the sub-optimal (23°C) and very sub-optimal (18°C) temperatures, respectively, of which 110 genes are commonly shared between the two stress conditions. The construction of a Highest Reciprocal Rank-based gene co-expression network, followed by its partition using a Heuristic Cluster Chiseling Algorithm resulted in 6 and 7 gene modules in sub-optimal and very sub-optimal temperature stresses being identified, respectively. Modules of sub-optimal temperature stress are principally enriched with carbohydrate and lipid metabolic processes, while most of the modules of very sub-optimal temperature stress are significantly enriched with responses to stimuli and various metabolic processes. Several transcription factors (from MYB, NAC, WRKY, WHIRLY & GATA classes) that may regulate the downstream genes involved in response to stimulus in order for the plant to withstand very sub-optimal temperature stress were highlighted. The identified gene modules could be useful in breeding for low-temperature stress tolerant bambara groundnut varieties

A Bacterial Acetyltransferase Destroys Plant Microtubule Networks and Blocks Secretion

The eukaryotic cytoskeleton is essential for structural support and intracellular transport, and is therefore a common target of animal pathogens. However, no phytopathogenic effector has yet been demonstrated to specifically target the plant cytoskeleton. Here we show that the Pseudomonas syringae type III secreted effector HopZ1a interacts with tubulin and polymerized microtubules. We demonstrate that HopZ1a is an acetyltransferase activated by the eukaryotic co-factor phytic acid. Activated HopZ1a acetylates itself and tubulin. The conserved autoacetylation site of the YopJ / HopZ superfamily, K289, plays a critical role in both the avirulence and virulence function of HopZ1a. Furthermore, HopZ1a requires its acetyltransferase activity to cause a dramatic decrease in Arabidopsis thaliana microtubule networks, disrupt the plant secretory pathway and suppress cell wall-mediated defense. Together, this study supports the hypothesis that HopZ1a promotes virulence through cytoskeletal and secretory disruption

Potential of High Resolution Electrical Resistivity Tomography to Detect Fractured Zones in Limestone and Dolomites Formations in the Near Subsurface at the Tournemire Experimental Platform, France

International audienc

High Resolution Electrical Resistivity Tomography in Superficial Limestones at Tournemire Site, France

International audienc

[Effects of delay in onset of revascularisation strategies in the acute phase of myocardial infarction].

International audiencethrombolysis (THL) and primary percutaneous coronary intervention (PCI) are therapeutic options in acute myocardial infarction (MI). These strategies have similar efficiency, particularly in the early phase. However, in these randomized studies, different times to treatment (TT) threshold are recognized as discriminant