The transcription factor NAC102 confers cadmium tolerance by regulating WAKL11 expression and cell wall pectin metabolism in Arabidopsis

Cadmium(Cd) toxicity severely limits plant growth and development. Moreover, Cd accumulation in vegetables, fruits, and food crops poses health risks to animals and humans. Although the root cell wall has been implicated in Cd stress in plants, whether Cd binding by cell wall polysaccharides contributes to tolerance remains controversial, and the mechanism underlying transcriptional regulation of cell wall polysaccharide biosynthesis in response to Cd stress is unknown. Here, we functionally characterized an Arabidopsis thaliana NAC-type transcription factor, NAC102, revealing its role in Cd stress responses. Cd stress rapidly induced accumulation of NAC102.1, the major transcript encoding functional NAC102, especially in the root apex. Compared to wild type(WT) plants, a nac102 mutant exhibited enhanced Cd sensitivity, whereas NAC102.1-overexpressing plants displayed the opposite phenotype. Furthermore, NAC102 localizes to the nucleus, binds directly to the promoter of WALL-ASSOCIATED KINASE-LIKE PROTEIN11(WAKL11), and induces transcription, thereby facilitating pectin degradation and decreasing Cd binding by pectin. Moreover, WAKL11 overexpression restored Cd tolerance in nac102mutants to the WT levels, which was correlated with a lower pectin content and lower levels of pectin-bound Cd. Taken together, our work shows that the NAC102-WAKL11 module regulates cell wall pectin metabolism and Cd binding, thus conferring Cd tolerance in Arabidopsis.

Alleviation by abscisic acid of Al toxicity in rice bean is not associated with citrate efflux but depends on ABI5-mediated signal transduction pathways

Under conditions of aluminum(Al) toxicity,which severely inhibits root growth in acidic soils, plants rapidly alter their gene expression to optimize physiological fitness for survival. Abscisic acid(ABA) has been suggested as a mediator between Al stress and gene expression, but the underlying mechanisms remain largely unknown. Here,we investigated ABA-mediated Al-stress responses, using integrated physiological and molecular biology approaches.We demonstrate that Al stress caused ABA accumulation in the root apex of rice bean(Vigna umbellata [Thunb.] Ohwi &Ohashi), which positively regulated Al tolerance. However,this was not associated with known Al-tolerance mechanisms. Transcriptomic analysis revealed that nearly one-third of the responsive genes were shared between the Al-stress and ABA treatments. We further identified a transcription factor, ABI5, as being positively involved in Al tolerance. Arabidopsis abi5 mutants displayed increased sensitivity to Al, which was not related to the regulation of AtALMT1 and AtMATE expression. Functional categorization of ABI5-mediated genes revealed the importance of cell wall modification and osmoregulation in Al tolerance, a finding supported by osmotic stress treatment on Al tolerance. Our results suggest that ABA signal transduction pathways provide an additional layer of regulatory control over Al tolerance in plants.

Typical atmospheric haze during crop harvest season in northeastern China：A case in the Changchun region

This study presents the mass concentrations of PM（2.5）,O3,SO2 and NOxat one urban,one suburban and two rural locations in the Changchun region from September 25 to October 272013. Major chemical components of PM（2.5）at the four sites were daily sampled and analyzed. Most of daily concentrations of SO2（7–82 μg/m^3）,O3（27–171 μg/m^3） and NOx（14–213 μg/m^3） were below the limits of the National Ambient Air Quality Standard（NAAQS）in China. However,PM（2.5）concentrations（143–168 μg/m^3） were 2-fold higher than NAAQS.Higher PM（2.5）concentrations（~ 150 μg/m^3） were measured during the pre-harvest and harvest at the urban site,while PM（2.5）concentrations significantly increased from 250 to400 μg m^（-3） at suburban and rural sites with widespread biomass burning. At all sites,PM（2.5）components were dominated by organic carbon（OC） and followed by soluble component sulfate（SO4^（2-））,ammonium（NH4~＋） and nitrate（NO3^-）. Compared with rural sites,urban site had a higher mineral contribution and lower potassium（K~＋and K） contribution to PM（2.5）.Severe atmospheric haze events that occurred from October 21 to 23 were attributed to strong source emissions（e.g.,biomass burning） and unfavorable air diffusion conditions.Furthermore,coal burning originating from winter heating supply beginning on October 18 increased the atmospheric pollutant emissions. For entire crop harvest period,the Positive Matrix Factorization（PMF） analysis indicated five important emission contributors in the Changchun region,as follows： secondary aerosol（39%）,biomass burning（20%）,supply heating（18%）,soil/road dust（14%） and traffic（9%）.