Abstract: Radish is an important vegetable crop. Leaf color mutant of radish is an excellent germplasm for breeding new radish varieties. Leaf color mutant is an ideal material for studying leaf colors, pigment synthesis, regulation mechanism of genetic development. This paper took a radish purple-red leaf mutant mu17 generated by chemical mutagenesis as material, and the wild type Ra9 as CK, and then determined the phenotypic characteristics, photosynthesis, chloroplast ultrastructure, pigment content and expression of related genes. The results showed that: the leaf of mu17 were purple-red in the whole vegetative growth period, and the growth was slow. Compared with Ra9, the stomatal conductance, intercellular CO₂ concentration, transpiration rate and the anthocyanin content of mu17 were significantly increased, but the net photosynthetic rate and the contents of chlorophyll a, chlorophyll b and carotenoids were significantly decreased. Therefore, it was speculated that the accumulation of anthocyanins and the decrease of chlorophyll content were the main factors resulting in the change of leaf color of mu17, were also the main reason for the decrease of photosynthesis and slow growth of mu17. Further analyses showed that the expression levels of RsCHI, RsCHS, RsF3H and RsMYB3, RsMYB4, RsMYB114, RsbHLH155 in mu17 were significantly difference from those in control Ra9. Therefore, it was speculated that transcription factors RsMYB and RsbHLH could promote the accumulation of anthocyanins in mu17 by regulating the expression levels of RsCHS, RsCHI and RsF3H. This study preliminarily explored the mechanism of leaf color change of radish color leaf from the physiological and molecular levels, which laid a good foundation for fine mapping and cloning of mutant genes, and provided theoretical basis for improving and breeding new radish varieties.

Key words: radish, leaf color mutant, photosyntheic characteristics, pigment content, expression analysis

摘要： 萝卜作为重要的蔬菜作物，其叶色突变体是培育萝卜新品种的优良种质，是进行叶片色彩变异、色素合成、遗传发育调控机制等一系列研究的理想材料。以化学诱变获得的能够稳定遗传的萝卜叶色突变体mu17为材料，以突变亲本Ra9为对照，观测其植物学性状，测定了光合特性、色素含量、叶绿体超微结构，并采用qRT-PCR检测叶片花青素代谢与调控路径相关基因的表达差异。结果显示：相比于同一时期的对照Ra9植株，萝卜突变体mu17的叶片在整个营养生长期内表现为紫红色，生长较为缓慢，气孔导度、胞间CO₂浓度、蒸腾速率明显升高，但净光合速率显著下降；叶绿素a、b与类胡萝卜素含量均低于对照Ra9，叶片花青素含量则显著高于对照Ra9。由此，推测花青素含量的积累和叶绿素含量的降低是突变体mu17叶色发生变化的主要因素，也是其光合作用下降、植株生长缓慢的主要原因。突变体mu17的花青素合成基因RsCHI、RsCHS、RsF3H及其调控基因RsMYB3、RsMYB4、RsMYB114、RsbHLH155表达水平，均与对照Ra9差异显著；推测RsMYB、RsbHLH等转录因子通过协同调控萝卜花青素合成相关基因RsCHS、RsCHI、RsF3H等的表达水平，促使紫红叶突变体花青素大量积累。上述从生理与分子水平上初步探究了萝卜彩叶突变体的叶色变化机理，为即将开展的突变基因精细定位与图位克隆奠定了良好基础，为改良和培育萝卜新品种提供了理论依据。

关键词: 萝卜, 叶色突变体, 光合特性, 色素含量, 表达分析