丛枝菌根真菌对大豆硒吸收的影响机制

Enshi is famous for its rich resource of selenium(Se) in China. How to develop and utilize the abundant local selenium is a challenge as well as a chance we are facing. Soybean, an important agricultural crop, has been reported to have capacity in selenium accumulation and provides selenium-enriched soybean protein for both human and animals.AM fungi are the important media for soybean in the uptake of soil nutrients. There are many reports on the role of AM fungi in the uptake of nitrogen and phosphorus, as well as in bioremediation. However, there are few reports about the influence of AM fungi on the selenium nutrition in soybean. In this project, changes of selenium-related metabolites and gene expression are investigated respectively by ICP-MS, HPLC-Q-TOF/MS , HPLC-Q-Trap/MS and RT-qPCR and Western blotting, which aims to demonstrate the influence of the symbiosis on uptake and metabolism of selenium in soybean. The transcriptomes of symbiotic and non-symbiotic soybean roots are sequenced by GS FLX to screen selenium-uptake related genes which are further analyzed by location and RNA interference. Based on the studies above, the influence mechanisms of symbiotic AM fungi on uptake and metabolism of selenium in soybean can be elucidated. The results can not only clarify the influence of AM fungi on the mechanisms of selenium-uptake and metabolism in soybean, but it can also provide a basis for developing the selenium resource by using soybean.

恩施是我国著名高硒区，如何开发利用本地区优势硒资源是我们面临的机遇和挑战。大豆是具有硒富集能力的重要作物，可为人畜提供优质的富硒大豆蛋白。AM真菌是大豆吸收土壤养分的重要媒介。AM真菌在植物氮、磷营养吸收及生物修复方面研究较多，而AM真菌对大豆硒营养的影响机制却鲜见报到。项目利用ICP-MS、HPLC-Q-TOF/MS、HPLC-Q-Trap/MS以及RT-qPCR和Western blotting等技术，从代谢和基因表达两方面研究AM真菌共生对大豆硒吸收代谢的影响。利用GS FLX测序平台对硒处理的共生与非共生大豆根转录组对比筛选硒吸收代谢相关候选基因，结合基因定位和RNAi干扰技术研究候选基因的功能。综合这两方面研究的结果来阐明共生的AM真菌对大豆硒吸收代谢的影响机制。项目结果既可阐明AM真菌对大豆吸收代谢硒营养过程中的作用机理，还可为利用大豆开发本地区优势硒资源奠定基础。

AM真菌在植物氮、磷营养吸收及生物修复方面研究较多，而AM真菌对植物硒吸收代谢的影响机制却鲜见报到。本研究比较硒处理的非共生和共生大豆中硒形态和硒代谢产物的变化情况，分析硒吸收代谢过程的变化；分析硒处理的非共生和共生大豆中硒吸收、转运及代谢关键酶基因表达的变化；对硒处理的非共生和共生大豆进行了转录组深度测序，比较归纳差异表达基因，分析其中与硒吸收、转运、代谢相关的候选基因表达变化；根据实验数据，结合前人研究结果，初步阐释了丛枝菌根真菌共生对大豆硒吸收影响的可能机制。取得重要结果如下：（1）在硒处理条件下，丛枝菌根真菌共生降低了大豆的硒吸收。（2）丛枝菌根真菌共生降低了大豆硒吸收的途径主要包括：A、丛枝菌根真菌可能通过丛枝菌根真菌膜上的硒/硫转运蛋白（SLC26D2和Sulp）和大豆质膜上的磷转运蛋白（PT1;3）的下调，降低植物硒含量；B、吸收进入大豆中的硒可能以挥发性的甲基硒醇（Methyl selenol）挥发，从而降低大豆中的硒含量；C、ABC转运蛋白家族基因表达上调，将液泡中贮存的硒转运出来参与代谢，形成有机形态的硒，或合成含硒氨基酸，或形成甲基硒醇挥发。（3）超聚硒植物碎米荠硒吸收代谢机制：A、硒酸根是植物体内硒代谢的起始形态；B、碎米荠耐受高浓度硒的机制主要在于硒化作用、液泡的贮藏功能、转氨作用以及含硒蛋白选择性降解。本项目结果初步阐释了髙硒环境下AM真菌降低大豆吸收的可能机理和超聚硒植物碎米荠的耐硒机制，不仅可为植物微量元素营养基础研究提供理论借鉴，还可为利用植物开发本地区优势硒资源提供理论支撑。