摘要： 为了了解Mo的分子功能，对26 000粒拟南芥EMS诱变突变体种子进行了筛选，鉴定出一个对正常Mo敏感的突变体4-10。在正常170 nmol/L Mo条件下，4-10突变体的根部伸长发育受到抑制，而340 μmol/L Mo处理能部分恢复突变体根长。在170 nmol/L Mo条件下4-10和Col-0幼苗的根长分别为（1.56±0.13） cm和（11.89±0.71） cm；而在340 μmol/L Mo条件下，4-10和Col-0的根长分别为（3.3±0.17） cm和（6.8±0.73） cm。此外，340 μmol/L Mo处理能够恢复4-10异常的根形态。Mo含量测定结果表明，4-10突变体植株根部Mo含量显著低于野生型植株；除了对正常Mo敏感外，4-10突变体叶色对NH₄⁺也敏感，其花青素含量显著高于Col-0。为了鉴定4-10突变体候选基因，利用图位克隆技术将候选基因定位到1号染色体一个23 kb区域（26.809~26.832 Mb），进一步基因组重测序结果表明，在该区域存在1个非同义突变SNP，包含该SNP的基因At1g71100编码核糖-5-磷酸异构酶（RPI），初步证明，RPI基因为4-10突变体的候选基因。利用AtRPI基因纯合突变植株和4-10突变体进行的等位性检测结果表明，4-10突变体和等位基因突变体rsw10-1杂交的F₁仍然对NH₄⁺敏感，从而确定RPI基因为4-10突变体基因。通过表型分析注意到除了过量Mo能恢复4-10突变体根长之外，外源尿苷处理同样可以恢复4-10突变体的根长。结果表明，过量的Mo通过尿苷转运作用促进了补救合成途径进程。

关键词: NH₄⁺, 拟南芥, 图位克隆, 钼, 补救合成途径

Abstract: In order to understand the molecular functions of molybdenum(Mo),a total of 26 000 seeds of Arabidopsis mutant mutagenized with ethylmethylsulfone(EMS)with alterations at normal Mo condition were identified and investigated. A mutant named 4-10,which was sensitive to normal Mo,was isolated. The root elongation of the 4-10 mutant was restored under the normal 170 nmol/L Mo condition and supply of 340 μmol/L Mo partially rescued root elongation. Under the 170 nmol/L Mo condition,the root length of 4-10 and Col-0 seedlings was(1.56±0.13)cm and (11.89±0.71)cm,respectively,while under 340 μmol/L Mo conditions,the root length of 4-10 and Col-0 was(3.3±0.17)cm and (6.8±0.73)cm. In addition,the abnormal root morphology of 4-10 could also be recovered by 340 μmol/L Mo treatment. Mo concentration measurement results showed that the root Mo concentration of 4-10 mutant was significantly lower than that of wild type. Besides the sensitivity to normal Mo,the leaf color of 4-10 mutant was also sensitive to NH₄⁺. Moreover,the leaves of 4-10 mutant had a higher anthocyanin contents than that of Col-0. To identify the causal gene of 4-10 mutant,the mutation was mapped to chromosome 1(between 26.809 and 26.832 Mb)using map-based cloning. Genome re-sequencing data showed that one mutation resulted in an amino acid substitution in At1g71100,encoded a ribose 5-phosphate isomerase(RPI),which revealed that RPI might be the causal gene of 4-10 mutant. To show that RPI is the causal gene of 4-10,a mutant line(rsw10-1)homozygous for a point mutation in the AtRPI gene was examined. rsw10-1 and F₁ plants from crosses between 4-10 and rsw10-1 displayed similar phenotype to 4-10 under NH₄⁺ condition,establishing that the mutation in the RPI gene was responsible for the phenotype. We noticed through phenotypic analysis that the root elongation of the mutant was not only recovered by addition of excess Mo but also by uridine. The results obtained indicated that excess Mo promote salvage pathway through the action of uridine transport.

Key words: NH₄⁺, Arabidopsis, Mapping, Molybdenum, Salvage pathway

中图分类号: 

• S335

• Q78