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| Inhibitory effects of root-applied growth-promoting Klebsiella sp. on cadmium uptake and accumulation in Brassica chinensis L. |
| Received:January 11, 2025 |
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| KeyWord:Klebsiella sp.;Brassica chinensis L.;cadmium;iron;nitrogen |
| Author Name | Affiliation | E-mail | | YANG Hao | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China
College of Resources and Environment, Northeast Agricultural University, Harbin 150030, China | | | WANG Changrong | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China | wangchangrong109@163.com | | WU Zhaoqinghua | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China | | | TIAN Geng | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China | | | WANG Lin | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China | | | HUANG Yongchun | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China | | | XUE Weijie | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China | | | SUN Yuebing | Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs(MARA)/Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin 300191, China | sunyuebing@caas.cn |
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| Abstract: |
| This study aimed to explore the impact of Klebsiella on the Cd accumulation characteristics in Brassica chinensis L. within contaminated soil. Utilizing Xialv No.2 Brassica chinensis L. as the experimental material, a combination of high-throughput sequencing of microorganisms, transcriptome sequencing, and step-wise extraction of soil Cd was employed. The research focused on investigating the effects of root-applied Klebsiella on the rhizosphere microbial community structure, soil physical and chemical properties, elemental morphology, as well as the regulation of Cd accumulation and functional gene expression in different organs of Brassica chinensis L. The results showed that the application of Klebsiella at the root promoted the growth of Brassica chinensis L. and significantly reduced the Cd content in the roots and shoots of Brassica chinensis L.. Compared with the CK treatment, the maximum reduction in the Cd content of the roots and shoots of Brassica chinensis L. was 44.6% and 22.5%, respectively. In the rhizosphere micro-environment, the Klebsiella treatment caused a slight elevation in soil pH and a decline in the bioavailability of Cd in the soil. Specifically, the content of the exchangeable fraction of Cd reduced by 6.0%, while the residual fraction of Cd rose by 8.0%. Meanwhile, Klebsiella accelerated the soil nitrogen mineralization process and significantly enhanced soil enzyme activity and inorganic nitrogen content. To be specific, the activities of soil urease, sucrase, catalase, nitrate reductase, and nitrite reductase increased by 19.5%, 20.5%, 27.7%, 42.9%, and 27.0%, respectively, and the contents of ammonium nitrogen, nitrate nitrogen, and alkali-hydrolyzed nitrogen increased by 56.7%, 39.6%, and 54.1%, respectively. Further, Klebsiella augmented the relative abundance of Verrucomicrobiota, Proteobacteria, Arthrobacter, Massilia, and Tychonema_CCAP_1459_11B, while reducing the relative abundance of Acidobacteriota and Actinobacteriota. The application of Klebsiella could lower the levels of Nramp and ZIP family genes associated with Cd transport by 17.6% - 20.5% and 44.8% - 77.4%, respectively. Additionally, the expression of ammonium nitrogen transporter and nitrogen - metabolism - related genes AMT, glnA, and nirA increased by 22.6% - 27.8%, 57.7%, and 29.7% - 37.7%, respectively. This promoted the absorption and utilization of inorganic nitrogen in Brassica chinensis L. roots and concurrently inhibited the absorption and transport of Cd. Klebsiella can boost the bioavailability of the nutrient element nitrogen, transform the form of iron oxide, and enhance its Cd-fixing capacity by regulating the cycles of nitrogen, iron, and other elements driven by the rhizosphere flora, thus reducing the availability of Cd in the soil. Moreover, microbial metabolism can suppress the expression of Cd-transport genes in Brassica chinensis L. roots and promote the expression of genes related to inorganic nitrogen absorption and metabolism. This is further beneficial for inhibiting the absorption and accumulation of Cd by Brassica chinensis L. and promoting its growth, which is of great significance for the safe production of Brassica chinensis L. in cadmium - contaminated farmland. |
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