关键词: 萝卜, 叶色突变体, 光合特性, 色素含量, 表达分析

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