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

CLC Number: 

• S335

• Q78