美國《國家科學(xué)院院刊》（PNAS）近日在線報道了澳大利亞昆士蘭大學(xué)和瑞士伯爾尼大學(xué)聯(lián)合研究團隊開展的關(guān)于“植物無需借助其他有機體就能利用蛋白質(zhì)作為氮源”的研究成果,。該成果不僅改變了人們對植物可利用氮源的看法,，同時也對植物完全依賴微生物和土壤菌類分解有機質(zhì)的固有認(rèn)識模式提出了挑戰(zhàn),。
氮是植物從土壤中定量獲取的最重要營養(yǎng)元素,。植物通過發(fā)達的根系從土壤中吸收、利用低分子態(tài)的氮化合物如銨態(tài)氮,、硝態(tài)氮和氨基酸,。然而，自然生態(tài)系統(tǒng)的土壤中,，氮主要以蛋白質(zhì)形式存在,，這種復(fù)雜的有機形態(tài)氮通常認(rèn)為是不能被植物直接利用的。不過,，該研究團隊重新審視了植物依靠特定的真菌菌根共生體進入土壤蛋白質(zhì)這種長期固有的觀念,，并以木本石楠荒原植物哈克木（Hakea actites）和草本植物擬南芥（Arabidopsisthaliana）為對象開展了研究，發(fā)現(xiàn)并沒有菌根形成,。這一研究結(jié)果表明這兩個物種無需借助其他有機體就能直接利用蛋白質(zhì)作為氮源,。隨后，該研究團隊進一步識別驗證了根系獲取利用蛋白質(zhì)的兩種機制：一是根系分泌蛋白水解酶消化了根表面和根皮層非原質(zhì)體上的蛋白質(zhì),；二是完整的蛋白質(zhì)也可能通過細(xì)胞的內(nèi)噬作用被吸收到根細(xì)胞內(nèi),。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
