拟南芥黄化突变体chlm-4的基因定位与分析

Mapping and Analysis of a Yellow Mutant chlm-4 of Arabidopsis thaliana (Cruciferae)

叶绿素是光合作用必需的重要色素,其合成需要Mg-原卟啉Ⅸ甲基转移酶等一系列酶的催化。我们通过筛选拟南芥EMS(乙基磺酸甲酯,ethyl-methane sulphonate)突变体库,分离到一个黄化突变体。该突变体叶绿素含量显著减少,叶绿体内垛叠的基粒缺失。遗传学分析表明,该突变体的黄化表型是由单基因控制的隐性性状。利用图位克隆的方法最终将基因定位在第IV条染色体分子标记F13M23和T30C3之间114kb的区间内,其中包含编码Mg-原卟啉Ⅸ甲基转移酶的CHLM基因。通过测序及等位分析表明该突变体是chlm的等位突变体,命名为chlm-4。在chlm-4中,CHLM蛋白的Gly59突变成Glu59,说明Gly59对于Mg-原卟啉Ⅸ甲基转移酶功能的行使是必需的。

Chlorophylls are essential for photosynthesis.Chlorophyll biosynthesis is catalyzed by a series of enzyme complexes,such as Mg-protoporphyrin IX methyltransferase.A yellow mutant of Arabidopsis was isolated using an enthyl-methane sulfonate （EMS） mutagenesis strategy.Chlorophyll content dramatically reduced and grana stacking was absent in the mutant.Genetic analysis indicated that the mutant was controlled by a single recessive gene.Using map-based cloning strategy,the gene responsible for the mutant phenotype was mapped to a region of 114 kb between the molecular markers F13M23 and T30C3 on chromosome 4,in which the CHLM gene encoding Mg-protoporphyrin IX methyltransferase was included.The mutant was proved to be an allelic mutant of CHLM gene by sequencing and allelism test and then was designated as chlm-4.Gly59 of CHLM was replaced by Glu59 in chlm-4,which indicated that Gly59 was essential for the function of Mg-protoporphyrin IX methyltransferase.