[Managing the cold chain in healthcare facilities]. / La maîtrise de la chaîne du froid en établissement de santé.

The storage of temperature-sensitive healthcare products requires control of the cold chain. Healthcare facilities must have the appropriate equipment at their disposal and ensure the traceability and monitoring of temperatures.

The build-up of osmotic stress responses within the growing root apex using kinematics and RNA-sequencing.

Molecular regulation of growth must include spatial and temporal coupling of cell production and cell expansion. The underlying mechanisms, especially under environmental challenge, remain obscure. Spatial patterns of cell processes make the root apex well suited to deciphering stress signaling pathways, and to investigating both processes. Kinematics and RNA-sequencing were used to analyze the immediate growth response of hydroponically grown Populus nigra cuttings submitted to osmotic stress. About 7400 genes and unannotated transcriptionally active regions were differentially expressed between the division and elongation zones. Following the onset of stress, growth decreased sharply, probably due to mechanical effects, before recovering partially. Stress impaired cell expansion over the apex, progressively shortened the elongation zone, and reduced the cell production rate. Changes in gene expression revealed that growth reduction was mediated by a shift in hormone homeostasis. Osmotic stress rapidly elicited auxin, ethylene, and abscisic acid. When growth restabilized, transcriptome remodeling became complex and zone specific, with the deployment of hormone signaling cascades, transcriptional regulators, and stress-responsive genes. Most transcriptional regulations fit growth reduction, but stress also promoted expression of some growth effectors, including aquaporins and expansins Together, osmotic stress interfered with growth by activating regulatory proteins rather than by repressing the machinery of expansive growth.

Tomato response traits to pathogenic Pseudomonas species: Does nitrogen limitation matter?

Induced chemical defence is a cost-efficient protective strategy, whereby plants induce the biosynthesis of defence-related compounds only in the case of pest attack. Plant responses that are pathogen specific lower the cost of defence, compared to constitutive defence. As nitrogen availability (N) in the root zone is one of the levers mediating the concentration of defence-related compounds in plants, we investigated its influence on response traits of tomato to two pathogenic bacteria, growing plants hydroponically at low or high N supply. Using two sets of plants for each level of N supply, we inoculated one leaf of one set of plants with Pseudomonas syringae, and inoculated the stem of other set of plants with Pseudomonas corrugata. Tomato response traits (growth, metabolites) were investigated one and twelve days after inoculation. In infected areas, P. syringae decreased carbohydrate concentrations whereas they were increased by P. corrugata. P. syringae mediated a redistribution of carbon within the phenylpropanoid pathway, regardless of N supply: phenolamides, especially caffeoylputrescine, were stimulated, impairing defence-related compounds such as chlorogenic acid. Inoculation of P. syringae produced strong and sustainable systemic responses. By contrast, inoculation of P. corrugata induced local and transient responses. The effects of pathogens on plant growth and leaf gas exchanges appeared to be independant of N supply. This work shows that the same genus of plant pathogens with different infection strategies can mediate contrasted plant responses.

Is the C:N ratio a reliable indicator of C allocation to primary and defence-related metabolisms in tomato?

Plant growth and defence are both fuelled by compounds synthesized from a common pool of carbon and nitrogen, implying the existence of a competition for carbon and nitrogen allocation to both metabolisms. The ratio of carbon to nitrogen (C:N) of an organ is often regarded as a convenient indicator of growth and quality. The purpose of this work was to assess whether or not it is possible to extend its use to characterize the trade-off between growth and defence processes. Therefore, we calculated C:N ratios in the pool of resources and in the total plant, and correlated them to the concentrations of diverse compounds of the primary and secondary metabolisms in young tomatoes. Plants were grown hydroponically at N availabilities either limiting (0.1 mM) or not (7 mM) for growth in two glasshouses maintained either under ambient or enriched (700 vpm) air CO(2). These conditions yielded a large array of C:N in fully developed leaves, developing leaves, stem and roots, sampled 27, 35 and 47 days after sowing. Growth parameters and tissue concentrations of primary metabolites (carbohydrates, starch), defence-related compounds (polyphenols, glycoalkaloids), lignin, nitrate, ammonium, C and N were analyzed. Net CO(2) exchange rate was also measured at the last sampling date. Low N limited plant growth more than photosynthesis. The C:N in the resource pool was far higher than the total C:N. Starch was the most responsive compound, attaining high concentration under high C:N, whereas lignin remained stable. Chlorogenic acid, rutin, kaempferol-rutinoside and tomatine concentrations correlated positively to C:N. The same patterns were observed for most organs and molecules, except soluble carbohydrates in fully developed leaves whose concentration was not influenced. Among the organs, developing leaves showed the highest concentrations of secondary compounds and were the most responsive to C:N variations. Neither the biochemical nature of the compounds (C-based or N- containing metabolites) nor the calculation mode of C:N, influenced the patterns observed. Within the range of N availabilities considered (up to N limitation but not deficiency), the C:N can be considered as a good indicator of the secondary compounds concentrations in organs, especially for those involved in the chemical defence.