美国《国家科学院院刊》（PNAS）近日在线报道了澳大利亚昆士兰大学和瑞士伯尔尼大学联合研究团队开展的关于“植物无需借助其他有机体就能利用蛋白质作为氮源”的研究成果。该成果不仅改变了人们对植物可利用氮源的看法，同时也对植物完全依赖微生物和土壤菌类分解有机质的固有认识模式提出了挑战。
氮是植物从土壤中定量获取的最重要营养元素。植物通过发达的根系从土壤中吸收、利用低分子态的氮化合物如铵态氮、硝态氮和氨基酸。然而，自然生态系统的土壤中，氮主要以蛋白质形式存在，这种复杂的有机形态氮通常认为是不能被植物直接利用的。不过，该研究团队重新审视了植物依靠特定的真菌菌根共生体进入土壤蛋白质这种长期固有的观念，并以木本石楠荒原植物哈克木（Hakea actites）和草本植物拟南芥（Arabidopsisthaliana）为对象开展了研究，发现并没有菌根形成。这一研究结果表明这两个物种无需借助其他有机体就能直接利用蛋白质作为氮源。随后，该研究团队进一步识别验证了根系获取利用蛋白质的两种机制：一是根系分泌蛋白水解酶消化了根表面和根皮层非原质体上的蛋白质；二是完整的蛋白质也可能通过细胞的内噬作用被吸收到根细胞内。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS，vol. 105 no. 11 4524-4529，Chanyarat Paungfoo-Lonhienne，Susanne Schmidt
Plants can use protein as a nitrogen source without assistance from other organisms
Chanyarat Paungfoo-Lonhienne, Thierry G. A. Lonhienne, Doris Rentsch, Nicole Robinson, Michael Christie, Richard I. Webb, Harshi K. Gamage, Bernard J. Carroll, Peer M. Schenk, and Susanne Schmidt
Nitrogen is quantitatively the most important nutrient that plants acquire from the soil. It is well established that plant roots take up nitrogen compounds of low molecular mass, including ammonium, nitrate, and amino acids. However, in the soil of natural ecosystems, nitrogen occurs predominantly as proteins. This complex organic form of nitrogen is considered to be not directly available to plants. We examined the long-held view that plants depend on specialized symbioses with fungi (mycorrhizas) to access soil protein and studied the woody heathland plant Hakea actites and the herbaceous model plant Arabidopsis thaliana, which do not form mycorrhizas. We show that both species can use protein as a nitrogen source for growth without assistance from other organisms. We identified two mechanisms by which roots access protein. Roots exude proteolytic enzymes that digest protein at the root surface and possibly in the apoplast of the root cortex. Intact protein also was taken up into root cells most likely via endocytosis. These findings change our view of the spectrum of nitrogen sources that plants can access and challenge the current paradigm that plants rely on microbes and soil fauna for the breakdown of organic matter.
