ALUMINUM TOLERANCE IN WHEAT (TRITICUM-AESTIVUM L) .2. ALUMINUM-STIMULATED EXCRETION OF MALIC-ACID FROM ROOT APICES
ALUMINUM TOLERANCE IN WHEAT (TRITICUM-AESTIVUM L) .2. ALUMINUM-STIMULATED EXCRETION OF MALIC-ACID FROM ROOT APICES
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DOI：
10.1104/pp.103.3.695
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发表时间：
1993-11-01
期刊：
影响因子：
7.4
通讯作者：
RANDALL, PJ
中科院分区：
文献类型：
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作者：
DELHAIZE, E;RYAN, PR;RANDALL, PJ
研究了有机酸在提高近等基因小麦(Triticum aestivum L.)耐铝性中的作用。耐铝性基因座(ALT1)上耐铝性不同的品系。在营养液中添加铝可促进小麦幼苗根中苹果酸和琥珀酸的分泌，耐铝品种的苹果酸分泌量是铝敏感品种的5~10倍。200 mU M Al暴露15min可检测到苹果酸排泄量，24 h后苹果酸排泄量呈线性增加，且苹果酸排泄量与外界铝浓度有关，低至10 mU M Al对苹果酸排泄量有刺激作用。在营养液中添加苹果酸能够保护铝敏感的幼苗免受正常植物毒害铝浓度的伤害。根尖(根尖3-5 mm)是苹果酸分泌的主要来源。耐铝和铝敏感幼苗的根尖在200亩铝暴露2小时之前和之后含有相似数量的苹果酸。在这种处理过程中，耐铝幼苗分泌的苹果酸总量大约是根尖中最初存在的总量的四倍，这表明甜菜酸的持续合成正在发生。Al能特异性地刺激苹果酸的分泌，La、Fe和PI的存在都不能引起这种反应。在耐铝性分离的苗木群体中，耐铝性与铝刺激的高苹果酸排泄率具有一致的相关性。这些数据与小麦的ALT1基因座编码基于铝刺激的苹果酸分泌的耐铝机制的假说是一致的。
We investigated the role of organic acids in conferring Al tolerance in near-isogenic wheat (Triticum aestivum L.) lines differing in Al tolerance at the Al tolerance locus (Alt1). Addition of Al to nutrient solutions stimulated excretion of malic and succinic acids from roots of wheat seedlings, and Al-tolerant genotypes excreted 5- to 10-fold more malic acid than Al-sensitive genotypes. Malic acid excretion was detectable after 15 min of exposure to 200 mu M Al, and the amount excreted increased linearly over 24 h. The amount of malic acid excreted was dependent on the external Al concentration, and excretion was stimulated by as little as 10 mu M Al. Malic acid added to nutrient solutions was able to protect Al-sensitive seedlings from normally phytotoxic Al concentrations. Root apices (terminal 3-5 mm of root) were the primary source of the malic acid excreted. Root apices of Al-tolerant and Al-sensitive seedlings contained similar amounts of malic acid before and after a 2-h exposure to 200 mu M Al. During this treatment, Al-tolerant seedlings excreted about four times the total amount of malic acid initially present within root apices, indicating that continual synthesis of melic acid was occurring. Malic acid excretion was specifically stimulated by Al, and neither La, Fe, nor the absence of Pi was able to elicit this response. There was a consistent correlation of Al tolerance with high rates of malic acid excretion stimulated by Al in a population of seedlings segregating for Al tolerance. These data are consistent with the hypothesis that the Alt1 locus in wheat encodes an Al tolerance mechanism based on Al-stimulated excretion of malic acid.