近日,華中農業大學理學院納米化學生物學課題組在納米酶調控活性氧增强大豆生物固氮研究方面取得新進展,相關成果以“Novel approach to enhance Bradyrhizobium diazoefficiens nodulation through continuous induction of ROS by manganese ferrite nanomaterials in soybean”為題發表在Journal of Nanobiotechnology上。
生物固氮為全球植物提供了75%的氮素。ROS過去一直被認為是植物代謝過程中的副產品,然而,越來越多的證據表明,ROS也是細胞信號轉導和調控的重要組成部分。豆科植物中的ROS通過直接或間接作用誘導結瘤基因的表達,是根瘤形成以及固氮的重要訊號分子。如何調控ROS水准,誘導豆科植物結瘤,從而延長結瘤時間,成為了生物固氮研究的新熱點。納米酶作為奈米科技與生物學之間的橋樑,為生物固氮研究提供了獨特的解決方案。
如圖1所示,韓鶴友教授團隊根據大豆生物固氮酶的結構特點,研究設計了一種新型的錳鐵納米酶,構建納米酶與大豆根瘤菌體系,通過持續調節ROS水准,延長結瘤期、新增根瘤數量,最終提高豆科植物共生固氮能力。
圖1.納米酶調控ROS促進豆科植物結瘤
圖2為納米酶處理大豆植物後的實驗結果:(1)根瘤重量和數量分別新增了50.85%和61.4%,單株固氮效率新增了151.36%,生物量積累新增了25.70%;(2)轉錄組測序分析顯示,在36個結瘤相關差异表達基因(DEGs)中,31個與大豆結瘤相關的DEGs在根瘤菌接種後期(12d)上調,表明納米酶處理大豆根瘤後,誘導結瘤相關基因(Nod-R)表達從而促進結瘤的新增。
圖2.不同濃度納米酶處理對豆科植物根的錶型和根瘤發育的影響
圖3.外源ROS調節結瘤和AON之間平衡的模型。
同時,為了評估納米酶處理對結瘤自調控(AON)通路的影響,本研究分析了通路中相關基因的表達差异,包括NFR1/NFR5(結瘤因數)、GmNINa(結瘤基因)、ENOD40s(結瘤反應基因)、NNC1(結瘤數量控制)、miR172c(微調根瘤菌感染和根瘤器官發生)、GmRIC1和GmRIC2(大豆中負責產生根源性結瘤的特定CLAVATA/ESR相關(CLE)肽)和GmNARK(根瘤自動調節受體激酶)(圖3)。結果表明:(1)納米酶處理組和對照組之間結瘤因數(NFR1/5)的表達較低且無顯著差异,這可能是外源ROS誘導的ROS表達基因下調導致的;(2)GmNINa、miR172c和ENOD40s均呈現上調趨勢,闡明了結瘤數目新增的機制;(3)在AON通路中,NARK對GmRIC2和GmRIC1表達的顯著上調沒有明顯反應,這可能是由於抑制了長距離運輸的CLE肽。
綜上所述,納米酶處理可以通過延長結瘤期、增强結瘤基因的表達、新增結瘤數量,提高生物固氮能力,並且不影響植物的營養生長或觸發結瘤的AON途徑。該研究為提高豆科植物共生固氮能力提供了新的策略。
博士研究生馬駿為論文第一作者,宋智勇副教授和韓鶴友教授為通訊作者。該研究得到了國家自然科學基金和國家重點研發計畫項目的資助。
【英文摘要】
Background
The study of symbiotic nitrogen fixation between(SNF)legumes and rhizobia has always been a hot frontier in scientific research.Nanotechnology provides a new strategy for biological nitrogen fixation research.However,how to construct abiotic nano-structure-biological system,using the special properties of nanomaterials,to realize the self-enhancement of biological nitrogen fixation capacity is important.
Results
In order to construct a more efficient SNF system,in this study,we applied manganese ferrite nanoparticles(MF-NPs)with sustainable diatomic catalysis to produce reactive oxygen species(ROS),thus regulating the nodulation pathway and increasing the number of nodules in soybean(Glycine max),eventually enhancing symbiotic nitrogen fixation.Symbiosis cultivation of MF-NPs and soybean plants resulted in 50.85% and 61.4% increase in nodule weight and number,respectively,thus inducing a 151.36% nitrogen fixation efficiency increase,finally leading to a 25.70% biomass accumulation increase despite no substantial effect on the nitrogenase activity per unit.Transcriptome sequencing analysis showed that of 36 differentially expressed genes(DEGs),31 DEGs related to soybean nodulation were upregulated in late rhizobium inoculation stage(12 d),indicating that the increase of nodules was derived from nodule-related genes(Nod-R)continuous inductions by MF-NPs.
Conclusions
Our results indicated that the nodule number could be effectively increased by extending the nodulation period without threatening the vegetative growth of plants or triggering the autoregulation of nodulation(AON)pathway.This study provides an effective strategy for induction of super-conventional nodulation.
原文連結:https://jnanobiotechnology.biomedcentral.com/articles/10.1186/s12951-022-01372-2