引用本文:李梦瑶,蒋湘艳,金海如.AM真菌共生系统中硝态氮吸收转运途径及对寄主生长的作用[J].土壤学报,2020,57(6):1483-1491. DOI:10.11766/trxb201909090476
LI Mengyao,JIANG Xiangyan,JIN Hairu.Modes of Uptake and Translocation of NO3- Affecting Growth of Host Plants in Arbuscular Mycorrhizal Symbiosis[J].Acta Pedologica Sinica,2020,57(6):1483-1491. DOI:10.11766/trxb201909090476
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AM真菌共生系统中硝态氮吸收转运途径及对寄主生长的作用
李梦瑶, 蒋湘艳, 金海如
浙江师范大学化学与生命科学学院
摘要:
利用AM真菌( Glomus intraradices)与毛根农杆菌质粒DNA转化的胡萝卜根(Ri T-DNA transformed carrotroots)建立的双重培养系统,以及同位素示踪技术探究AM真菌共生系统中硝态氮NO3-转运吸收途径,对铵态氮和硝态氮吸收合成精氨酸进行研究;并开展农田试验研究铵态氮和硝态氮吸收转运对寄主生长的影响。研究发现AM真菌菌丝在NH4+和NO3-共存时,优先吸收NH4+。当AM真菌的根外菌丝用NH415NO3处理1周时,虽然根外菌丝的自由氨基酸未被15N标记,包括精氨酸,但是菌根组织中的自由氨基酸被15N标记,揭示了15NO3沿着菌丝直接转运至菌根组织而不是来自于精氨酸转运的新模式;而根外菌丝用15NH4NO3处理时菌根组织中只有精氨酸被15N标记,而其他氨基酸合成的氮素主要来自菌丝室运转来的14 NO3,所以未被标记。AM真菌根外菌丝加13C6-葡萄糖,培养6周后,发现菌根组织的精氨酸和蛋白质均未发现13C,说明其根外菌丝不能利用葡萄糖。菌丝室加13C1,2-乙酸钠后,菌根组织的精氨酸和蛋白质均发现13C,分别为8.5%2.3%和7.6%0.7%,说明其根外菌丝能吸收利用乙酸盐中的碳素。菌丝室加13C1,2-乙酸钠+15NO3后,随着氮源的增加,其自由精氨酸浓度提高为54.2%19.3%,菌根蛋白质中精氨酸浓度变化不大;同时菌根组织的精氨酸和蛋白质中C/N同位素标记丰度大大提高,分别为57.4%4.8%和50.3%2.8%,说明菌丝室加碳源乙酸和氮源,可以提高精氨酸的合成。大田试验中,在低磷条件下,接种AM真菌并添加硝酸钾后菌根化甜玉米茎叶重明显提高,相比对照的甜玉米提高了12.28%;硫酸铵则不如硝酸钾对AM真菌菌根化甜玉米株重的促进作用,反而是降低了其生物量8.19%,尿素则降低了13.02%,但尿素再加有机肥则可以缓解对生物量的降低作用。
关键词:  丛枝菌根真菌  碳源  氮源  精氨酸  15N标记  13C标记
基金项目:国家自然科学基金项目(41371291)和浙江省公益技术应用研究计划项目(LGN20D010002)
Modes of Uptake and Translocation of NO3- Affecting Growth of Host Plants in Arbuscular Mycorrhizal Symbiosis
LI Mengyao, JIANG Xiangyan, JIN Hairu
College of Chemistry and life sciences, Zhejiang normal University
Abstract:
【Objective】Effects of uptake and translocation of NO3- in arbuscular mycorrhizal symbiosis and formation of arginine(Arg) in extraradical mycelium(ERM) and mycorrhizal root when ERM was exposed to NO3-or NH4+, affecting growth of their host plants were studied. 【Method】In this study a dual split culture system was established with Ri T- DNA transformed carrot root and Glomus intraradices(Rhizophagus intraradices) and the 15N/13C isotope tracing technique was used to explore pathways of the uptake and transport of NO3-, and determine how much arginine accumulated in ERM and mycorrhizal root after NO3- or NH4+ was absorbed and translocated in the fungal compartment, and a field experiment was conducted too to address how uptake and translocatiton of NO3-or NH4+ affect growth of the host plants. 【Result】Results show that AM hypha preferred to uptake NH4+ over NO3- when they both were available in the soil. When AM extraradical hypha were exposed to NH415 NO3- for 1 week, though the free amino acids, include Arg, in the extraradical mycelium (ERM) were not labelled by15N, those in the mycorrhizal tissues were, indicating that 15 NO3- in the fungal compartment were transported directly via mycelium into mycorrhizal tissues rather than any new translocation mode; on the contrary, when extraradical hypha were cultured with 15NH4 NO3-, only Arg was 15N-labelled therein, while the form of nitrogen composed of other amino acids in the ERM was 14NO3- translocated mainly from the hypha compartment and hence not labelled. While exposed to 13C6-Glucose for 6 weeks, the ERM was found to have no13C-labelled Arg or protein, which indicates that ERM is unable to utilize glucose. When exposed to 13C1,2-acatate, the ERM was found to have Arg and protein13C labelled up to 8.5%2.3% and 7.6%0.7%, respectively; when exposed to 13C1,2-acatate plus 15NO3-, the ERM increased the concentration of free Arg with increasing N input, up to 54.2%19.3% and 13C labelled Arg and protein up to 57.4%4.8% and 50.3%2.8%, respectively, which indicates that increased C and N inputs in the hypha compartment may promote formation of Arg. In the field experiment, in the field low in P level, addition of KNO3 increased significantly weight of the AM-inoculated sweet corm plants by 12.28%, as compared to the control, but addition of NH4SO4 did not have such an effect and instead decreased biomass of the plants by 8.19%, and addition of urea did by 13.02%; however amendment of organic manure to urea application mitigated the adverse effect.【Conclusion】There are two different modes of AM fungi absorbing and transporting ammonium and nitrate. AM fungi absorb and transport ammonium nitrogen (NH4+ and urea), via GS-GOGAT in ERM, and most of the absorbed nitrogen is integrated into Arg molecules, and the synthesized arginine is intactly transported to the intraradical mycelium by ERM. Meanwhile, NO3-in the AM fungi symbiosis, as revealed by the isotope tracing technique, is adsorbed by ERM and transported via ERM to intraradical mycelium. Application of NO3 may promote growth of the AM fungi-hosted sweet corn, while application of NH4+ may affect the crop reversely.
Key words:  Arbuscular mycorrhizal fungi  Carbon source  Nitrogen source  Arginine  15N labelling  13C labelling