Iuchi Satoshi, Koyama Hiroyuki, Iuchi Atsuko, Kobayashi Yasufumi, Kitabayashi Sadako, Kobayashi Yuriko, Ikka Takashi, Hirayama Takashi, Shinozaki Kazuo, Kobayashi Masatomo
BioResources Center, RIKEN, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074, Japan.
Proc Natl Acad Sci U S A. 2007 Jun 5;104(23):9900-5. doi: 10.1073/pnas.0700117104. Epub 2007 May 29.
Acid soil syndrome causes severe yield losses in various crop plants because of the rhizotoxicities of ions, such as aluminum (Al(3+)). Although protons (H(+)) could be also major rhizotoxicants in some soil types, molecular mechanisms of their tolerance have not been identified yet. One mutant that was hypersensitive to H(+) rhizotoxicity was isolated from ethyl methanesulfonate mutagenized seeds, and a single recessive mutation was found on chromosome 1. Positional cloning followed by genomic sequence analysis revealed that a missense mutation in the zinc finger domain in a predicted Cys(2)His(2)-type zinc finger protein, namely sensitive to proton rhizotoxicity (STOP)1, is the cause of hypersensitivity to H(+) rhizotoxicity. The STOP1 protein belongs to a functionally unidentified subfamily of zinc finger proteins, which consists of two members in Arabidopsis based on a Blast search. The stop1 mutation resulted in no effects on cadmium, copper, lanthanum, manganese and sodium chloride sensitivitities, whereas it caused hypersensitivity to Al(3+) rhizotoxicity. This stop1 mutant lacked the induction of the AtALMT1 gene encoding a malate transporter, which is concomitant with Al-induced malate exudation. There was no induction of AtALMT1 by Al(3+) treatment in the stop1 mutant. These results indicate that STOP1 plays a critical role in Arabidopsis tolerance to major stress factors in acid soils.
酸性土壤综合征会导致多种作物严重减产，这是由于离子（如铝离子（Al(3+)））的根际毒性所致。尽管在某些土壤类型中质子（H(+)）也可能是主要的根际毒素，但尚未确定植物对其耐受性的分子机制。从甲磺酸乙酯诱变的种子中分离出一个对H(+)根际毒性高度敏感的突变体，并发现其在1号染色体上存在一个隐性突变。通过定位克隆和基因组序列分析发现，预测的Cys(2)His(2)型锌指蛋白（即对质子根际毒性敏感（STOP）1）的锌指结构域中的一个错义突变，是对H(+)根际毒性高度敏感的原因。STOP1蛋白属于一个功能未知的锌指蛋白亚家族，基于Blast搜索，拟南芥中该亚家族由两个成员组成。stop1突变对镉、铜、镧、锰和氯化钠的敏感性没有影响，但对Al(3+)根际毒性表现出超敏反应。这个stop1突变体缺乏对编码苹果酸转运蛋白的AtALMT1基因的诱导，而该诱导与铝诱导的苹果酸分泌相关。在stop1突变体中，Al(3+)处理不会诱导AtALMT1。这些结果表明，STOP1在拟南芥对酸性土壤中主要胁迫因子的耐受性中起关键作用。
