MtESN2 is a subgroup II sulphate transporter required for symbiotic nitrogen fixation and prevention of nodule early senescence in Medicago truncatula.

Adequate distribution of mineral sulphur (S) nutrition to nodules mediated by sulphate transporters is crucial for nitrogen fixation in symbiosis establishment process. However, the molecular mechanisms underlying this process remain largely unknown. In this study, we characterized the function of Early Senescent Nodule 2 (MtESN2), a gene crucial to nitrogen fixation in Medicago truncatula. Mutations in MtESN2 resulted in severe developmental and functional defects including dwarf shoots, early senescent nodules, and lower nitrogenase activity under symbiotic conditions compared to wild-type plants. MtESN2 encodes an M. truncatula sulphate transporter that is expressed only in roots and nodules, with the highest expression levels in the transition zone and nitrogen-fixing zone of nodules. MtESN2 exhibited sulphate transport activity when expressed in yeast. Immunolocalization analysis showed that MtESN2-yellow fluorescent protein fusion protein was localized to the plasma membranes of both uninfected and infected cells of nodules, where it might transport sulphate into both rhizobia-infected and uninfected cells within the nodules. Our results reveal an unreported sulphate transporter that contributes to effective symbiosis and prevents nodule early senescence in M. truncatula.

MicroRNAs modulate adaption to multiple abiotic stresses in Chlamydomonas reinhardtii.

MicroRNAs play an important role in abiotic stress responses in higher plants and animals, but their role in stress adaptation in algae remains unknown. In this study, the expression of identified and putative miRNAs in Chlamydomonas reinhardtii was assessed using quantitative polymerase chain reaction; some of the miRNAs (Cre-miR906-3p) were up-regulated, whereas others (Cre-miR910) were down-regulated when the species was subjected to multiple abiotic stresses. With degradome sequencing data, we also identified ATP4 (the d-subunit of ATP synthase) and NCR2 (NADPH: cytochrome P450 reductase) as one of the several targets of Cre-miR906-3p and Cre-miR910, respectively. Q-PCR data indicated that ATP4, which was expressed inversely in relation to Cre-miR906-3p under stress conditions. Overexpressing of Cre-miR906-3p enhanced resistance to multiple stresses; conversely, overexpressing of ATP4 produced the opposite effect. These data of Q-PCR, degradome sequencing and adaptation of overexpressing lines indicated that Cre-miR906-3p and its target ATP4 were a part of the same pathway for stress adaptation. We found that Cre-miR910 and its target NCR2 were also a part of this pathway. Overexpressing of Cre-miR910 decreased, whereas that of NCR2 increased the adaption to multiple stresses. Our findings suggest that the two classes of miRNAs synergistically mediate stress adaptation in algae.

Functionalization of sawdust with monosodium glutamate for enhancing its malachite green removal capacity.

In this paper, waste sawdust was functionalized by monosodium glutamate for improving its cationic sorption capacity. The functionalized sawdust (FS) and crude sawdust (CS) were compared for their malachite green (MG) sorption behaviors with a batch system. The effects of various experimental parameters (e.g. initial pH, sorbent dose, dye concentration, contact time, and temperature etc.) were investigated and the sorption kinetic and thermodynamic characteristics were understood. The MG removal ratios on FS and on CS increased with increasing initial pH and came up to the maximum value beyond pH 6 for FS and pH 8 for CS, respectively. The ratio of sorbed MG kept above 95% for 250 mg/l of MG solution when 2.0 g/l or more of FS was used. The MG removal percentage decreased more on CS than on FS with increasing initial MG concentration. The isothermal data of MG sorbed on FS and on CS followed the Langmuir model. By functionalizing, the sorption capacity (Q(m)) of sawdust for MG was increased from 85.47 to 196.08 mg/g and the sorption equilibrium time of MG was shortened from 23 to 4.5 h. The MG sorption processes on FS and on CS followed the pseudo-second-order rate kinetics. The sorptions of MG on FS and on CS were spontaneous and exothermic processes and lower temperatures were favorable for the sorption processes.