Diazotrophic Paenibacillus beijingensis BJ-18 Provides Nitrogen for Plant and Promotes Plant Growth, Nitrogen Uptake and Metabolism
Diazotrophic Paenibacillus beijingensis BJ-18 Provides Nitrogen for Plant and Promotes Plant Growth, Nitrogen Uptake and Metabolism
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固氮型北京类芽孢杆菌BJ-18为植物提供氮素，促进植物生长、氮素吸收和代谢
DOI：
10.3389/fmicb.2019.01119
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发表时间：
2019-05-29
影响因子：
5.2
通讯作者：
Chen, Sanfeng
中科院分区：
文献类型：
--
作者：
Li, Yongbin;Li, Yunlong;Chen, Sanfeng
固氮菌可以将N2还原为植物有效铵（NH 4+），促进植物生长，减少氮（N）肥料需求。然而，固氮菌对生物固氮贡献率和寄主植物氮素吸收代谢的影响还很少有系统的研究。以小麦、玉米和黄瓜为材料，研究了固氮类芽孢杆菌BJ-18在低氮和高氮土壤中对小麦、玉米和黄瓜的影响，并以未接种的植株为对照。本研究表明，GFP标记的北京青霉BJ-18定殖于幼苗内外，在根、茎和叶中形成根际和内生菌落。接种植物中该细菌的数量取决于土壤氮水平。在低氮条件下，接种显著增加了地上部干重（小麦86.1%，玉米46.6%，黄瓜103.6%）和根干重（小麦46.0%，玉米47.5%，黄瓜20.3%）。~（15）N同位素富集实验表明，植物幼苗从生物固氮中获得的氮占12.9-36.4%。低氮土壤中nifH基因的转录水平是高氮土壤中的0.75-1.61倍。接种促进了土壤中NH 4+和NO3-的吸收，尤其是在低N条件下。低氮条件下，接种植株的全氮量增加49.1-92.3%，高氮条件下，接种植株的全氮量增加13-15.5%。接种提高了植株的谷氨酰胺合成酶（GS）和硝酸还原酶（NR）活性，特别是在低氮条件下。在低氮条件下，氮吸收和氮代谢相关基因AMT（铵转运蛋白）、NRT（硝酸盐转运蛋白）、NiR（亚硝酸盐还原酶）、NR、GS和GOGAT（谷氨酸合成酶）的表达量上调1.5-91.9倍，而在高氮条件下，这些基因的表达量变化不明显。综上所述，北京拟青霉BJ-18是一株高效的内生固氮菌。该菌能促进植物固氮，促进植物生长和氮素吸收，提高植物氮素吸收和同化相关基因的表达和酶活性。然而，这些对植物的积极影响受到土壤氮素状况的调节。这项研究可能会提供深入了解植物与有益的联合和内生固氮细菌的相互作用。
Diazotrophic bacteria can reduce N2 into plant-available ammonium (NH4+), promoting plant growth and reducing nitrogen (N) fertilizer requirements. However, there are few systematic studies on the effects of diazotrophic bacteria on biological N2 fixation (BNF) contribution rate and host plant N uptake and metabolism. In this study, the interactions of the diazotrophic Paenibacillus beijingensis BJ-18 with wheat, maize, and cucumber were investigated when it was inoculated to these plant seedlings grown in both low N and high N soils, with un-inoculated plants as controls. This study showed that GFP-tagged P. beijingensis BJ-18 colonized inside and outside seedlings, forming rhizospheric and endophytic colonies in roots, stems, and leaves. The numbers of this bacterium in the inoculated plants depended on soil N levels. Under low N, inoculation significantly increased shoot dry weight (wheat 86.1%, maize 46.6%, and cucumber 103.6%) and root dry weight (wheat 46.0%, maize 47.5%, and cucumber 20.3%). The 15N-isotope-enrichment experiment indicated that plant seedlings derived 12.9–36.4% N from BNF. The transcript levels of nifH in the inoculated plants were 0.75–1.61 folds higher in low N soil than those in high N soil. Inoculation enhanced NH4+ and nitrate (NO3-) uptake from soil especially under low N. The total N in the inoculated plants were increased by 49.1–92.3% under low N and by 13–15.5% under high N. Inoculation enhanced activities of glutamine synthetase (GS) and nitrate reductase (NR) in plants, especially under low N. The expression levels of N uptake and N metabolism genes: AMT (ammonium transporter), NRT (nitrate transporter), NiR (nitrite reductase), NR, GS and GOGAT (glutamate synthase) in the inoculated plants grown under low N were up-regulated 1.5–91.9 folds, but they were not obviously changed under high N. Taken together, P. beijingensis BJ-18 was an effective, endophytic and diazotrophic bacterium. This bacterium contributed to plants with fixed N2, promoted plant growth and N uptake, and enhanced gene expression and enzyme activities involved in N uptake and assimilation in plants. However, these positive effects on plants were regulated by soil N status. This study might provide insight into the interactions of plants with beneficial associative and endophytic diazotrophic bacteria.