Molecular mechanisms of drought resistance using genome-wide association mapping in maize (Zea mays L.).

BACKGROUND: Drought is a critical abiotic stress that influences maize yield and reduces grain yield when it occurs at the flowering or filling stage. To dissect the genetic architecture of grain yield under drought stress (DS), a genome-wide association analysis was conducted in a maize population composed of diverse inbred lines from five locations under well-watered and DS conditions at flowering in 2019 and 2020. RESULTS: Using a fixed and random model circulating probability unification model, a total of 147 loci associated with grain yield or the drought resistance index (DRI) were identified, of which 54 loci were associated with a DRI with an average phenotypic variation explanation of 4.03%. Further, 10 of these loci explained more than 10% of the phenotypic variation. By integrating two public transcriptome datasets, 22 differentially expressed genes were considered as candidate genes, including the cloned gene ZmNAC49, which responds to drought by regulating stomatal density. Enrichment and protein interaction network showed that signaling pathways responded to drought resistance, including jasmonic acid and salicylic acid, mitogen-activated protein kinase, and abscisic acid-activated. Additionally, several transcription factors involved in DS were identified, including basic leucine zipper (GRMZM2G370026), NAC (GRMZM2G347043), and ethylene-responsive element binding protein (GRMZM2G169654). CONCLUSIONS: In this study, we nominated several genes as candidate genes for drought resistance by intergrating association maping and transcription analysis. These results provide valuable information for understanding the genetic basis of drought tolerance at the mature stage and for designing drought-tolerant maize breeding.

VO2-based superposed Fabry-Perot multilayer film with a highly enhanced infrared emittance and emittance tunability for spacecraft thermal control.

Thermal control coating for spacecraft based on thermochromic film attracts increasing interest due to their ability of self-adaptive emittance switch and less resource consuming compared with traditional thermal control coatings. However, practical applications of thermochromic film for spacecraft are constrained by the low infrared emittance at a high temperature and narrow emittance tunability. In this work, a thermochromic film with simple structure, nearly perfect infrared emission and large emittance tunability is proposed for the application of spacecraft thermal control. The thermochromic film is a VO2-based superposed Fabry-Perot (FP) multilayer film, which is constructed by encapsulating three thin VO2 layers in four lossless BaF2 spacer on the Al substrate. The infrared emittance and emittance tunability of the superposed FP film is dramatically enhanced by the three superposed VO2-BaF2-Al FP resonances at wavelengths of 9, 15 and 20 µm, respectively. For VO2 layers under metallic state, the spectral normal emittance of the superposed FP film is close to unity in the entire mid-infrared spectral range, while for VO2 layers under dielectric state, the film is highly reflective. For the typical growth techniques of the VO2 layers considered here, the emittance tunability of the superposed FP film can exceed 0.70 with total normal emittance larger than 0.91 at high temperature, simultaneously. The largest total normal emittance of the superposed FP film can reach 0.95 with emittance tunability of 0.78. In addition, the infrared emission and emittance tunability performances of the superposed FP film remain excellent for incident angles up to 60°. This work proposes a simple structure with highly enhanced infrared emittance and emittance tunability that outperforms the existing thermochromic films, which could accelerate the application of thermochromic films in the field of spacecraft thermal control.

Fast start-up of expanded granular sludge bed (EGSB) reactor using stored Anammox sludge.

Stored Anammox sludge (SAS) was used in an expanded granular sludge bed (EGSB) reactor treating synthetic wastewater with the aim of evaluating its possible use as seed sludge. The SAS had been kept in a refrigerator (4 °C) without any feed. After 2 years, only 1-2% Anammox bacteria could survive in the SAS. However, it soon prevailed in the EGSB reactor after loading. Accordingly, the start-up of the EGSB reactor was successfully completed in 34 days. The biomass turned to round reddish granular sludge from irregular brown floc at the end of this study. The results indicate that SAS could serve well as seed sludge. The required time for start-up of the Anammox reactor using SAS was thus demonstrated to be shorter than that of uncultivated sludge under experimental conditions.

PVA-gel beads enhance granule formation in a UASB reactor.

PVA-gel beads were used as a biocarrier in a lab-scale UASB reactor treating synthetic wastewater composed of corn steep liquor (CSL) with the aim of evaluating its use as a growth nucleus to enhance granule formation. Over 117 days of operation, the organic loading rate was increased to 22.5kgCOD/m3/day with an influent COD of about 10.8g/L at an HRT of 12h with COD removal efficiencies greater than 87%. By the end of the study period, the PVA-gel turned black and granule formation was achieved as compared with the formation of much fewer natural granules without the PVA-gel nucleus. No filamentous bacteria were found on the surface or interior of the PVA-gel beads. The PVA-gel granules had an average settling velocity 200m/h (5cm/s), and a biomass attachment of 0.93g VSS/g PVA-gel. The required time for formation of PVA-gel granules was thus demonstrated to be shorter than that of ordinary sludge granules under the experimental conditions used in this study.