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Extensive lead (Pb) accumulation in plants exerts toxic effects on plant growth and development and enters the human food chain. Combining linkage mapping, transcriptome analysis, and association studies, we cloned the ZmbZIP54 transcription factor, which confers maize tolerance to Pb. Combined overexpression and knockdown confirmed that ZmbZIP54 mitigates Pb toxicity in maize by alleviating Pb absorption into the roots. Yeast one-hybrid and dual-luciferase assays revealed that ZmbZIP54 binds to the ZmPRP1 promoter and promotes its transcription. Yeast two-hybrid and bimolecular fluorescence complementation assays indicated that ZmFdx5 interacts with ZmbZIP54 in the nucleus. ZmFdx5 acts as a switch that controls the regulation of ZmPRP1 expression by ZmbZIP54 when maize encounters Pb stress. Furthermore, we revealed that variation in the 5'-UTR of ZmbZIP54 affects its expression level under Pb stress and contributes to the difference in Pb tolerance among maize lines. Finally, we proposed a model to summarize the role of ZmbZIP54 in Pb tolerance, which involves the cooperative effect of ZmbZIP54 and ZmFdx5 on the ZmPRP1 transcription in maize response to Pb. This study provides novel insights into the development of Pb-tolerant maize varieties and bioremediation of Pb-contaminated soils.

Lead (Pb) is one of the most toxic heavy metal pollutants, which can penetrate to plant cells via root absorption and thus cause irreversible damages to the human body through the food chain. To identify the hub gene responsible for Pb tolerance in maize, we performed a trait-associated co-expression network analysis at a genome-wide level, using two maize lines with contrasting Pb tolerances. Finally, ZmNRAMP6 that encodes a metal transporter was identified as the hub gene among the Pb tolerance-associated co-expression module. Heterologous expression of ZmNRAMP6 in yeast verified its role in Pb transport. Combined Arabidopsis overexpression and maize mutant analysis suggested that ZmNRAMP6 conferred plant sensitivity to Pb stress by transporting Pb ion from the roots to shoots. Knockout of ZmNRAMP6 caused Pb retention in the roots and activation of the antioxidant enzyme system, resulting in an increased Pb tolerance in maize. An integration of yeast one-hybrid and dual-luciferase reporter assay uncovered that ZmNRAMP6 was negatively regulated by a known Pb tolerance-related transcript factor ZmbZIP54. Different from the other known NRAMP genes, ZmNRAMP6 acted as a Pb transporter from the roots to shoots and environment. Collectively, knockout of ZmNRAMP6 will aid in the bioremediation of contaminated soil and food safety guarantee of forage and grain corn.

The ability of immature maize (Zea mays) embryos to form embryonic calluses (ECs) is highly genotype dependent, which limits transgenic breeding development in maize. Here, we report the association map-based cloning of ZmSAUR15 using an association panel (AP) consisting of 309 inbred lines with diverse formation abilities for ECs. We demonstrated that ZmSAUR15, which encodes a small auxin-upregulated RNA, acts as a negative effector in maize EC induction. Polymorphisms in the ZmSAUR15 promoter that influence the expression of ZmSAUR15 transcripts modulate the EC induction capacity in maize. ZmSAUR15 is involved in indole-3-acetic acid biosynthesis and cell division in immature embryo-derived callus. The ability of immature embryos to induce EC formation can be improved by the knockout of ZmSAUR15, which consequently increases the callus regeneration efficiency. Our study provides new insights into overcoming the genotypic limitations associated with EC formation and improving genetic transformation in maize.

In this paper, the bending and buckling analysis of microbeam with the uniform and non-uniform cylindrical cross-section was examined based on the classical beam theory and the modified couple stress theory to model the micro-structures effects. The nonlinear effect of the Von-Karman theory is regarded to study the large-deflection effect on the buckling of microtubes. The conservation energy principle is used to derive the nonlinear equation of motion and the boundary conditions. The effect of several applicable cross-sections, including the linear, exponential, and convex function, on the static behavior of cylindrical beam is investigated, which is made by the porosity-dependent axially functionally graded material. The homotopy perturbation technique as a semi-analytical solution, coupled with the generalized differential quadrature method, is employed to obtain the nonlinear results. Eventually, the influence of various parameters such as the porosity, volume fraction index, bending load, nonlinear deflection, length-scale effect on the bending deflection, and buckling of microbeam with both clamped and pinned supported are analyzed in details.

The heavy metals lead and cadmium have become important pollutants in the environment, which exert negative effects on plant morphology, growth and photosynthesis. It is particularly significant to uncover the genetic loci and the causal genes for lead and cadmium tolerance in plants. This study used an IBM Syn10 DH population to identify the quantitative trait loci (QTL) controlling maize seedling tolerance to lead and cadmium by linkage mapping. The broad-sense heritability of these seedling traits ranged from 65.8–97.3% and 32.0–98.8% under control (CK) and treatment (T) conditions, respectively. A total of 53 and 64 QTL were detected under CK and T conditions, respectively. Moreover, 42 QTL were identified using lead and cadmium tolerance coefficient (LCTC). Among these QTL, five and two major QTL that explained > 10% of phenotypic variation were identified under T condition and using LCTC, respectively. Furthermore, eight QTL were simultaneously identified by T and LCTC, explaining 5.23% to 9.21% of the phenotypic variations. Within these major and common QTL responsible for the combined heavy metal tolerance, four candidate genes (Zm00001d048759, Zm00001d004689, Zm00001d004843, Zm00001d033527) were previously reported to correlate with heavy metal transport and tolerance. These findings will contribute to functional gene identification and molecular marker-assisted breeding for improving heavy metal tolerance in maize.

Pb can damage the physiological function of human organs by entering the human body via food-chain enrichment. Revealing the mechanisms of maize tolerance to Pb is critical for preventing this. In this study, a Pb-tolerant maize inbred line, 178, was used to analyse transcription factors (TFs) expressed under Pb stress based on RNA sequencing data. A total of 464 genes expressed in control check (CK) or Pb treatment samples were annotated as TFs. Among them, 262 differentially expressed transcription factors (DETs) were identified that responded to Pb treatment. Furthermore, the DETs were classified into 4 classes according to their expression patterns, and 17, 12 and 2 DETs were significantly annotated to plant hormone signal transduction, basal transcription factors and base excision repair, respectively. Seventeen DETs were found to participate in the plant hormone signal transduction pathway, where basic leucine zippers (bZIPs) were the most significantly enriched TFs, with 12 members involved. We further obtained 5 Arabidopsis transfer DNA (T-DNA) mutants for 6 of the maize bZIPs, among which the mutants atbzip20 and atbzip47, representing ZmbZIP54 and ZmbZIP107, showed obviously inhibited growth of roots and above-ground parts, compared with wild type. Five highly Pb-tolerant and 5 highly Pb-sensitive in maize lines were subjected to DNA polymorphism and expression level analysis of ZmbZIP54 and ZmbZIP107. The results suggested that differences in bZIPs expression partially accounted for the differences in Pb-tolerance among the maize lines. Our results contribute to the understanding of the molecular regulation mechanisms of TFs in maize under Pb stress.

Objectives This study sought to evaluate the safety and efficacy of rosuvastatin in preventing contrast-induced acute kidney injury (CI-AKI) in patients with diabetes mellitus (DM) and chronic kidney disease (CKD). Background CI-AKI is an important complication after contrast medium injection. While small studies have shown positive results with statin therapy, the role of statin therapy in prevention of CI-AKI remains unknown. Methods We randomized 2,998 patients with type 2 DM and concomitant CKD who were undergoing coronary/peripheral arterial angiography with or without percutaneous intervention to receive rosuvastatin, 10 mg/day (n = 1,498), for 5 days (2 days before, and 3 days after procedure) or standard-of-care (n = 1,500). Patients' renal function was assessed at baseline, 48 h, and 72 h after exposure to contrast medium. The primary endpoint of the study was the development of CI-AKI, which was defined as an increase in serum creatinine concentration ≥0.5 mg/dl (44.2 μmol/l) or 0.25% above baseline at 72 h after exposure to contrast medium. Results Patients randomized to the rosuvastatin group had a significantly lower incidence of CI-AKI than controls (2.3% vs. 3.9%, respectively; p = 0.01). During 30 days' follow-up, the rate of worsening heart failure was significantly lower in the patients treated with rosuvastatin than that in the control group (2.6% vs. 4.3%, respectively; p = 0.02). Conclusions Rosuvastatin significantly reduced the risk of CI-AKI in patients with DM and CKD undergoing arterial contrast medium injection. (Rosuvastatin Prevent Contrast Induced Acute Kidney Injury in Patients With Diabetes [TRACK-D]; NCT00786136 )