Transcriptomic, proteomic, and physiological studies reveal key players in wheat nitrogen use efficiency under both high and low nitrogen supply.

The effective use of available nitrogen (N) to improve crop grain yields provides an important strategy to reduce environmental N pollution and promote sustainable agriculture. However, little is known about the common genetic basis of N use efficiency (NUE) at varying N availability. Two wheat (Triticum aestivum L.) cultivars were grown in the field with high, moderate, and low N supply. Cultivar Zhoumai 27 outperformed Aikang 58 independent of the N supply and showed improved growth, canopy leaf area index, flag leaf surface area, grain number, and yield, and enhanced NUE due to both higher N uptake and utilization efficiency. Further, transcriptome and proteome analyses were performed using flag leaves that provide assimilates for grain growth. The results showed that many genes or proteins that are up- or down-regulated under all N regimes are associated with N and carbon metabolism and transport. This was reinforced by cultivar differences in photosynthesis, assimilate phloem transport, and grain protein/starch yield. Overall, our study establishes that improving NUE at both high and low N supply requires distinct adjustments in leaf metabolism and assimilate partitioning. Identified key genes/proteins may individually or concurrently regulate NUE and are promising targets for maximizing crop NUE irrespective of the N supply.

Heavy metal accumulation and health risk assessment in soil-wheat system under different nitrogen levels.

Heavy metal(loid)s (HMs) in organic fertilizer have become a primary source of HMs pollution of farmlands, which could cause deleterious health effects in people exposed through soil-plant systems via multi-pathways. This study investigated China's main grain production area (Henan Province) to evaluate the accumulation and transport characteristics of HMs (Cr, Mn, Ni, Cu, Zn, As, Cd and Pb) in a soil-wheat system and conduct a health risk assessment for wheat (Triticum aestivum) grain under different nitrogenous fertilizer treatments. The results indicated that the Cr, Cu, As and Cd contents in soil were 56.21-113.66, 13.97-58.72, 5.79-22.62 and 0.04-0.23mg·kg-1, and the mean contents of Cr and As contents in wheat grains were 0.78±0.31 and 0.49±0.18mg·kg-1, respectively, which exceeded the corresponding standards. The bio-concentration factor and transfer factor were lowest in response to N-fertilization with N8-N15. Health risk assessment showed that the local population who ingested grain from culture condition of N15 experienced the lowest non-cancer and cancer risks. Among different population groups, HMs posed relatively higher non-cancer and cancer risks to children aged 0-5years. Furthermore, Cr and As exposure was the greatest contributor to Hazard Index (HI), accounting for 74.72-83.11%, while Cr exposure accounted for >90% of the total potential cancer risk. Concluding, this study indicated that, to protect human health, the current application of nitrogenous fertilizer should be controlled to an appropriate level.