TaNAC48 positively regulates drought tolerance and ABA responses in wheat(Triticum aestivum L.)

NAC family transcription factors(TFs) are important regulators in plant development and stress responses. However, the biological functions of NAC TFs in wheat are rarely studied. In this study, 43 putative drought-induced NAC genes were identified from de novo transcriptome sequencing data of wheat following drought treatment. Twelve wheat NACs along with ten known stress-related NACs from Arabidopsis and rice were clustered into Group II based on a phylogenetic analysis. Ta NAC48, which showed a higher and constitutive expression level in Group Ⅱ, was selected for further investigation.Ta NAC48 transcript was up-regulated by drought, PEG, H_(2)O_(2) and abscisic acid(ABA) treatment and encoded a nuclear localized protein. Overexpression of Ta NAC48 significantly promoted drought tolerance with increased proline content, and decreased rates of water loss, malondialdehyde(MDA), H_(2)O_(2) and O_(2)^(-) content. Root length and a stomatal aperture assay confirmed that Ta NAC48-overexpression plants increased sensitivity to ABA. Electrophoretic mobility shift assay(EMSA) and luciferase reporter analysis indicated that Ta AREB3 could bind to a cis-acting ABA-responsive element(ABRE) on Ta NAC48 promoter and activate the expression of Ta NAC48. These results suggest that Ta NAC48 is essential in mediating crosstalk between the ABA signaling pathway and drought stress responses in wheat.

Flavonol synthase gene MsFLS13 regulates saline-alkali stress tolerance in alfalfa

Alfalfa(Medicago sativa L.) is one of the most extensively grown leguminous forage worldwide.Environmental saline-alkali stress significantly influences the growth,development,and yield of alfalfa,posing a threat to its agricultural production.However,little is known about the potential mechanisms by which alfalfa responds to saline-alkali stress.Here,we investigated these mechanisms by cloning a saline-alkali-induced flavonol synthase gene(Ms FLS13) from alfalfa,which was previously reported to be significantly upregulated under saline-alkali stress,and examining its function in the saline-alkali response.Overexpression of Ms FLS13 in alfalfa promoted plant tolerance to saline-alkali stress by enhancing flavonol accumulation,antioxidant capacity,osmotic balance,and photosynthetic efficiency.Conversely,Ms FLS13 inhibition using RNA interference reduced flavonol synthase activity and inhibited hairy root growth under saline-alkali stress.Yeast one-hybrid and dual-luciferase reporter assays indicated that the R2R3-MYB Ms MYB12 transcription factor activates Ms FLS13 expression by binding to the MBS motif in the Ms FLS13 promoter.Further analysis revealed that abscisic acid mediates the salinealkali stress response partially by inducing Ms MYB12 and Ms FLS13 expression,which consequently increases flavonol levels and maintains antioxidant homeostasis in alfalfa.Collectively,our findings highlight the crucial role of Ms FLS13 in alfalfa in response to saline-alkali stress and provide a novel genetic resource for creating saline-alkali-resistant alfalfa through genetic engineering.

Effects of tourmaline on nitrogen removal performance and biofilm structures in the sequencing batch biofilm reactor

The effects of tourmaline on nitrogen removal performance and biofilm structures were comparatively investigated in two identical laboratory-scale sequencing batch biofilm reactors（SBBRs）（denoted SBBR1 and SBBR2） at different nitrogen loading rates（NLRs） varying from（0.24 ± 0.01） to（1.26 ± 0.02） g N/（L·day）. SBBR1 was operated in parallel with SBBR2, but SBBR1 was filled with polyurethane foam loaded tourmaline（TPU） carriers and another（SBBR2） filled with polyurethane foam（PU） carriers. Results obtained from this study showed that the excellent and stable performance of SBBR1 was obtained. Ammonia nitrogen removal and total nitrogen removal were higher in SBBR1 than that in SBBR2 with increase of NLR. At an NLR of（0.24 ± 0.01） g N/（L·day）, the majority of the spherical and elliptical bacteria were surrounded by the extracellular polymeric substance（EPS） and bacillus or filamentous bacteria in two SBBRs biofilms. When NLR increased to（1.26 ± 0.02） g N/（L·day）, the clusters were more obvious in the SBBR1 biofilm than that in the SBBR2 biofilm. Bacteria in SBBR1 were inclined to synthesis more EPS, and the formed EPS could protect the bacteria from free ammonia（FA） under extreme condition NLR（1.26 ± 0.02） g N/（L·day）. The results of polymerase chain reaction-denaturing gradient gel electrophoresis analysis showed that the microbial community similarity in SBBR2 decreased more obviously than that in SBBR1 with the increase of NLR, which the microbial community in SBBR1 was relatively stable.