Response of chemical properties, microbial community structure and functional genes abundance to seasonal variations and human disturbance in Nanfei River sediments.

The Nanfei River, located in Hefei City, Anhui Province, subjected to increased nutrient loads from point and/or non-point source. Little is known about the indicators indicating heterogeneity of surface sediments. We aimed to identify the suitable indicators that can reflect the sediment heterogeneity by analyzing the sensitivity of sediment physicochemical properties group, microbial communities and diversity indices group and C, N, S-functional genes group to seasonal and regional changes. River sediments from different areas (urban area, urban-rural fringe and rural area) were collected in the level, dry and wet seasons, respectively. The chemical parameters had most significant regional heterogeneity, but no seasonal differences. Seasons had a greater impact on the overall microbial community structure than the areas. Specifically, the relative abundance of Firmicutes and Bacteroidetes were more sensitive to seasonal changes. Overall, seasonal changes showed the greatest impact on the functional genes group, with the S-functional genes (dsrB and aprA) group providing the clearest seasonal variation. Considering the seasonal distribution of functional genes and their sensitivity to environmental factors, we speculated that the sulfate-reducing gene (dsrB), the methanogenic gene (mcrA) and the anammox gene (hzo) could be identified as sensitive indicators to indicate the seasonal heterogeneity of surface sediments in different river sections of the same river in the short term. We also concluded that environmental variables were more conducive to indicating the regional heterogeneity of sediments. This study provided a valuable reference for assessing the heterogeneity or ecological stress of river sediments.

The spatial and seasonal variations of bacterial community structure and influencing factors in river sediments.

Studying the composition and structure of bacterial communities in sediments helps to understand the contribution of bacteria to environmental changes and the role of feedback in response to disturbances. However, seasonal changes in bacterial communities of river sediments with different pollution levels and sources have not been clear yet. In this study, we collected sediment samples during the dry season, wet season and level season from 40 sites with various pollution sources in three inflow rivers (Fengle-Hangbu River, Nanfei River and Zhegao River) of Chaohu Lake. Bacterial community compositions were determined based on high-throughput sequencing. The 'Bioenv' in the R package 'Vegan' and redundancy analysis was used to explore the influence of environmental factors on the bacterial community in the river sediments. Results showed that a significant deviation in bacterial communities was found among seasons and rivers. In addition, seasonal dynamics had a greater impact on shaping bacterial communities than rivers with different pollution sources. A higher diversity was found in the wet season as compared to the other seasons. The bacterial diversity was negatively correlated with nutrients (OM, TN, NH4+, IP, OP and TP) and metals (Cu and Zn). Bacterial communities were more sensitive to heavy metals pressure than nutrients. We also concluded that heavy metals (Cu and Cd) were the key contributing factors in explaining variations in bacterial communities. This study provided a valuable reference for assessing ecological stress.

Mutation of a histidine-rich calcium-binding-protein gene in wheat confers resistance to Fusarium head blight.

Head or ear blight, mainly caused by Fusarium species, can devastate almost all staple cereal crops (particularly wheat), resulting in great economic loss and imposing health threats on both human beings and livestock1-3. However, achievement in breeding for highly resistant cultivars is still not satisfactory. Here, we isolated the major-effect wheat quantitative trait locus, Qfhs.njau-3B, which confers head blight resistance, and showed that it is the same as the previously designated Fhb1. Fhb1 results from a rare deletion involving the 3' exon of the histidine-rich calcium-binding-protein gene on chromosome 3BS. Both wheat and Arabidopsis transformed with the Fhb1 sequence showed enhanced resistance to Fusarium graminearum spread. The translation products of this gene's homologs among plants are well conserved and might be essential for plant growth and development. Fhb1 could be useful not only for curbing Fusarium head blight in grain crops but also for improving other plants vulnerable to Fusarium species.