Effects of Funnelliformis mosseae inoculation on alleviating atrazine damage in Canna indica L. var. flava Roxb

Noval bio-organic fertilizer containing Arthrobacter sp. DNS10 alleviates atrazine-induced growth inhibition on soybean by improving atrazine removal and nitrogen accumulation

Herbicide atrazine restricts nutrient accumulation and thus inhibits the growth of sensitive crops. The application of organic fertilizer is a common measure that contributes to modulating abiotic tolerance of crops and providing nutrients, but its advantages in combination with atrazine degrading microorganisms as bio-organic fertilizer to alleviate atrazine stress on sensitive crops and the associated mechanisms are unknown. We investigated the beneficial effects of organic and bio-organic fertilizer (named DNBF10) containing Arthrobacter sp. DNS10 applications on growth, leaf nitrogen accumulation, root surface structure and root physiological properties of soybean seedlings exposed to 20 mg kg^-1 atrazine in soil. Compared with organic fertilizer, bio-organic fertilizer DNBF10 exhibited more reduction in soil atrazine residue and plant atrazine accumulation, as well as alleviation in atrazine-induced root oxidative stress and damaged cells of soybean roots. Transcriptome analysis revealed that DNBF10 application enhanced nitrogen utilization by improving the expression of genes involved in nitrogen metabolism in soybean leaves. Besides, genes expression of cytochrome P450 and ABC transporters involved in atrazine detoxification and transport in soybean leaves were also down-regulated by DNBF10 to diminish phytotoxicity of atrazine to soybean seedlings. These results illustrate the molecular mechanism by which the application of DNBF10 alleviates soybean seedlings growth under atrazine stress, providing a step forward for mitigate the atrazine induced inhibition on soybean seedlings growth through decreasing atrazine residues as well as enhancing damaged root repair and nitrogen accumulation.

Diverse and abundant arbuscular mycorrhizal fungi in ecological floating beds used to treat eutrophic water

An increasing number of investigations have shown the universal existence of arbuscular mycorrhizal fungi (AMF) in aquatic ecosystems. However, little is known about the accurate distribution and function of AMF inhabiting aquatic ecosystems, especially ecological floating beds (EFBs), which are constructed for the remediation of polluted water bodies. In this study, we collected root samples of Canna generalis, Cyperus alternifolius, and Eichhornia crassipes from three EFBs on two eutrophic lakes in Wuhan, China. We aimed to investigate the resources and distribution of AMF in EFBs using Illumina Mi-seq technology. A total of 229 operational taxonomic units (OTUs) and 21 taxa from 348,799 Glomeromycota sequences were detected. Glomus and Acaulospora were the most dominant and second most dominant genera of AMF in the three EFBs, respectively. Different aquatic plant species showed varying degrees of AMF colonization (3.83-71%), diversity (6-103 OTUs, 3-15 virtual taxa), and abundance (14-57,551 sequences). Low AMF abundance, but relatively high AMF diversity, was found in C. alternifolius, which is usually considered non-mycorrhizal. This finding indicated the high accuracy of Illumina sequencing. Our results also revealed a lognormal species abundance distribution that was observed across AMF taxa in the three plant species. The AMF community composition was closely related to nitrogen and phosphorus contents. Overall, our data show that EFBs harbor diverse and abundant AMF communities. Additionally, the AMF community composition is closely related to the water quality of eutrophic lakes treated by the EFBs, indicating the potential application of AMF in plant-based bioremediation of wastewater. KEYPOINTS: • Aquatic plants in EFBs harbor diverse (229 OTUs) and abundant (348,799 sequences) AMF. • Different plant species host different taxa of AMF. Cyperaceae, originally considered non-mycorrhizal, may in fact be a variable mycorrhizal plant family. • The AMF community composition in EFBs is closely related to nutrient concentrations (nitrogen and phosphorus).

Responses of nonenzymatic antioxidants to atrazine in arbuscular mycorrhizal roots of Medicago sativa L

Atrazine induces the production of reactive oxygen species (ROS), which are detoxified by enzymatic and nonenzymatic mechanisms in plants. Arbuscular mycorrhizal fungi improve on this first level of plant resistance to environmental stresses through the antioxidant defense system, but the way in which nonenzymatic antioxidants relate to atrazine in arbuscular mycorrhizal roots is not well-known. In this study, a symbiotic relationship between Funneliformis mosseae and Medicago sativa L. roots was established successfully. Then, a non-targeted metabolite analysis which was hypothesis-free concerning particular metabolites was used to provide a comprehensive metabolic fingerprint and to subsequently identify, quantify, and finally find different nonenzymatic antioxidants in mycorrhizal and non-mycorrhizal roots following atrazine addition. Tocotrienol, (iso)flavonoids, and their derivate concentrations in F. mosseae-M. sativa mycorrhizal roots were significantly higher than in non-mycorrhizal roots. The majority of (iso)flavonoids and their derivates increased significantly via methylation or glycosylation, but dehydroascorbic acid in its oxidized form decreased significantly in mycorrhizal roots. In general, F. mosseae colonization results in significantly greater nonenzymatic antioxidant tocotrienol and (iso)flavonoids derivate concentrations in M. sativa roots, which may be associated with resistance to atrazine.