The exogenous application of AtPGLR, an endo-polygalacturonase, triggers pollen tube burst and repair.

Plant cell wall remodeling plays a key role in the control of cell elongation and differentiation. In particular, fine-tuning of the degree of methylesterification of pectins was previously reported to control developmental processes as diverse as pollen germination, pollen tube elongation, emergence of primordia or elongation of dark-grown hypocotyls. However, how pectin degradation can modulate plant development has remained elusive. Here we report the characterization of a polygalacturonase (PG), AtPGLR, the gene for which is highly expressed at the onset of lateral root emergence in Arabidopsis. Due to gene compensation mechanisms, mutant approaches failed to determine the involvement of AtPGLR in plant growth. To overcome this issue, AtPGLR has been expressed heterologously in the yeast Pichia pastoris and biochemically characterized. We showed that AtPGLR is an endo-PG that preferentially releases non-methylesterified oligogalacturonides with a short degree of polymerization (< 8) at acidic pH. The application of the purified recombinant protein on Amaryllis pollen tubes, an excellent model for studying cell wall remodeling at acidic pH, induced abnormal pollen tubes or cytoplasmic leakage in the subapical dome of the pollen tube tip, where non-methylesterified pectin epitopes are detected. Those leaks could either be repaired by new ß-glucan deposits (mostly callose) in the cell wall or promoted dramatic burst of the pollen tube. Our work presents the full biochemical characterization of an Arabidopsis PG and highlights the importance of pectin integrity in pollen tube elongation.

Medicago truncatula Phytoglobin 1.1 controls symbiotic nodulation and nitrogen fixation via the regulation of nitric oxide concentration.

In legumes, phytoglobins (Phytogbs) are known to regulate nitric oxide (NO) during early phase of the nitrogen-fixing symbiosis and to buffer oxygen in functioning nodules. However, their expression profile and respective role in NO control at each stage of the symbiosis remain little-known. We first surveyed the Phytogb genes occurring in Medicago truncatula genome. We analyzed their expression pattern and NO production from inoculation with Sinorhizobium meliloti up to 8 wk post-inoculation. Finally, using overexpression and silencing strategy, we addressed the role of the Phytogb1.1-NO couple in the symbiosis. Three peaks of Phytogb expression and NO production were detected during the symbiotic process. NO upregulates Phytogbs1 expression and downregulates Lbs and Phytogbs3 ones. Phytogb1.1 silencing and overexpression experiments reveal that Phytogb1.1-NO couple controls the progression of the symbiosis: high NO concentration promotes defense responses and nodular organogenesis, whereas low NO promotes the infection process and nodular development. Both NO excess and deficiency provoke a 30% inhibition of nodule establishment. In mature nodules, Phytogb1.1 regulates NO to limit its toxic effects while allowing the functioning of Phytogb-NO respiration to maintain the energetic state. This work highlights the regulatory role played by Phytogb1.1-NO couple in the successive stages of symbiosis.

[2015 literature findings in general internal medicine]. / Médecine ambulatoire en 2015: moins est parfois mieux!

Benzodiazepines are associated with the risk of developing Alzheimer's disease. Systematic dosage and vitamin D substitution have no place in times of immediate post-menopause. Topical placebos challenge analgesics in the treatment of knee osteoarthritis. Palliative chemotherapy does not improve life-quality at the end of life. Restrictive transfusion thresholds entail no risk. Spirometry should always be performed before the initiation of a long-term bronchodilator therapy. Practitioners continue to overprescribe antibiotics for infections of the upper respiratory tract. Pap test may soon be replaced by HPV urinary testing. Without increasing costs, a telephone triage by the primary care physician can reduce the number of consultations.

[Doctor, I have pain and pins and needles in my legs at night]. / "Docteur, j'ai mal et des fourmis dans les jambes le soir...".

Restless legs syndrome (RLS) is a frequent chronic condition. It causes discomfort in the lower limbs with an urge to move the legs and sometimes paresthesias. It's frequently associated with sleep and mood disorders causing a significant impact on quality of life. There are four clinical criteria to diagnose it. Treatment includes management of reversible factors and if needed symptomatic treatment. Depending on symptoms severity, non-drug measures can be tried. First-line medication treatment should be dopaminergic agonists. Second-line treatments include, anticonvulsivants (gabapentine), benzodiazepine (clonazepam) or opioids based on predominant symptoms. Difficult cases should be referred to a specialist.