完整植株共生系统中N、P耦合对AM真菌精氨酸运转及铵传递的作用机制

Arbuscular mycorrhizal fungi is an obligate symbiont associated with over 80% terrestrial plants,able to absorb inorganic N,amino acids-N,the assimilated N then is transported along the mycelium in the form of arginine, which has been confirmed in Ri T-DNA transformed carrot root colonized with AM fungi. The translocated arginine is degraded and release NH4+ in intraradical hyphae, then transferred to the host plant for further utilization.However, under the soil environment and whole plant symbiotic system the effect of coupling of N,P(includs host plant and soil environment) on nitrogen uptake,arginine translocation and ammonium transfer via AM fungi is unknown and need further investigation. As such, effect of coupling of N and P under different soil N P concentration, host plant N P ratios,various N forms and AM strains on the mechanism of N uptake,arginine translocation and NH4 transfer to host plant require further studies in detail. Moreover, at the molecule level, the activities of arginase for degradation of arginine during N uptake and translocation in AM and plant symbiosis in soil should be measured.Also, at the molecular level, analysis of gene expression coding ammonium transporter in host plant root cortical cell will be carried out to reveal the mechanism on how NH4+ transferred to the host plant is regulated under the coupling of N and P. These works will provide the basis for application of AM biofertilizer in agricultural to gain best mycorrhizal biofertilizer benefits.

AM真菌与陆地上80%以上植物专性共生，近来研究发现了其吸收的氮在菌丝中以精氨酸形态运转，以铵的形式传递给寄主细胞利用。但AM真菌是否能吸收利用肽类以及在完整的植株系统中N、P（包括植物和土壤）耦合对共生ＡＭ真菌氮吸收和精氨酸运转及铵传递的影响还不清楚。于是，将用15N标记的谷胱甘肽和蛋白质进行同位素示踪实验证明其对有机氮的利用情况。同时，需要深入研究土壤不同NP水平、寄主植物不同NP比例、不同氮素形态和不同共性特性ＡＭ真菌菌株下N、P耦合对AM真菌运转精氨酸和传递氮素给寄主植物的影响；同时在分子水平需要进一步研究氮磷耦合（包括寄主和土壤）对氮传递的关键酶精氨酸分解酶酶活，以及铵输运蛋白（AMT）编码基因在植物根皮细胞中表达水平的影响，从而揭示AM真菌运转氮素载体精氨酸和向寄主植物传递铵的作用机制。

AM真菌与陆地上80%以上植物专性共生，能吸收无机氮、氨基酸，并在ＡＭ真菌与离体根器官共生的无菌培养系统中研究发现了其吸收的氮在菌丝中以精氨酸形态运转，以铵的形式传递给寄主细胞利用,最近也研究了氮素载体精氨酸的代谢调节机制。但是在完整的植株系统中N、P（包括植物和土壤）耦合对共生ＡＭ真菌氮吸收和精氨酸运转及铵传递的影响还不清楚。于是，需要深入研究土壤不同NP水平、寄主植物不同NP比例、不同氮素形态和不同共性特性ＡＭ真菌菌株下N、P耦合对AM真菌运转精氨酸和传递氮素给寄主植物的影响；同时在分子水平需要进一步研究氮磷耦合（包括寄主和土壤）对氮传递的关键酶精氨酸分解酶酶活，以及铵输运蛋白（AMT）编码基因在植物根皮细胞中表达水平的影响，从而揭示AM真菌运转氮素载体精氨酸和向寄主植物传递铵的作用机制，为ＡＭ真菌作为菌根生物肥料发挥最大的肥效奠定基础。