摘要
对各种含氮基质、葡萄糖和(或)根浸出液中培养的丛枝菌根真菌Glomus intraradices孢子,在萌发过程中对不同氮素的利用及其氨基酸的生物合成进行了研究.用稳定同位素标记及质谱仪来分析不同氮素的利用和氨基酸的生物合成.以高效液相色谱测量氨基酸的浓度.在缺少外源氮素的情况下,丛枝菌根真菌孢子萌发时可以利用内部储存的含氮化合物生物合成游离氨基酸.其中,丝氨酸和甘氨酸是大量合成的氨基酸.合成的氨基酸浓度在2周内随着萌发时间的增加而增加.在有可利用的外源无机氮(铵盐、硝酸盐和尿素)和有机氮(氨基酸)时,铵盐和尿素比硝酸盐更容易被AM真菌萌发孢子利用,而其利用氨基酸中的氮比无机氮源慢的多.孢子吸收同化外源无机氮,且将其整合到游离氨基酸中,这些新生氨基酸浓度比无外源氮添加时要高得多.在无葡萄糖添加的硝酸盐培养液中,AM真菌孢子中积累大量天冬酰胺.然而,在含有葡萄糖的培养液中,萌发孢子因葡萄糖的吸收促进了对外源氮的吸收,产生的游离氨基酸是无葡萄糖时的5倍,并且发现精氨酸转为含量最多的游离氨基酸.并且,从外源氮吸收同化的氮可以储存于精氨酸中,随之,精氨酸被整合到AM真菌孢子储存的蛋白质中.此外,根浸出原液在AM真菌孢子萌发2周后对氮的吸收作用不明显.
Nitrogen utilization and amino acids biosynthesis were examined in germinating spores of AM fungus Glomus intraradices Schenck ＆ Smith after exposure to various N substrates, glucose and/or root exudates. N uptake and de novo amino acids biosynthesis were analyzed using stable isotopic labeling with mass spectrometric detection. HPLC-based analysis was used to measure amino acid levels. In the absence of exogenous nitrogen sources, germinating AM fungal spores utilized internal storage N compounds for biosynthesis of free amino acids, among which serine and glycine were abundantly produced. Their concentrations increased as germination time increasing from 0 to 7 or 14 days. On the availabilities of inorganic N（ ammonium, nitrate, urea） and organic N （amino acids）, ammonium and urea were preferred to nitrate and N from amino acids was assimilated more slowly than from inorganic sources by AM fungal spores. Exogenous inorganic N was readily assimilated and incorporated into internal free amino acids which reached much higher levels than the control of no exogenous N, espeacially abundant asparagine was accumulated in AM spores when exposed to nitrate and fed without exogenous glucose; however, in glucose-fed germinating spores, uptake of exogenous nitrogen sources were enhanced and more than 5 times free amino acids were produced comparing to the control of no glucose, among which arginine was in turn to be the most abundant free amino acid and further incorporated into proteins of AM fungal spores as storage N compounds. In addition, raw root exudates didn＇t significantly affect the amount of nitrogen uptake by AM spores after germination for 2 wks.
出处
《中国科学：生命科学》
CSCD
北大核心
2010年第3期239-249,共11页
Scientia Sinica(Vitae)
基金
国家自然科学基金(批准号:30970101)
浙江省科技厅科技计划(批准号:2006C22009)资助项目
关键词
从枝菌根真菌
孢子萌发
同位素标记
氮代谢
葡萄糖
根浸出液
Arbuscular mycorrhizas, germinating spores, isotopic labeling, nitrogen metabolism, glucose, root exudates
