Beijing Key Laboratory of Ornamental Plants Germplasm Innovation & Molecular Breeding, National Engineering Research Center for Floriculture, Beijing Laboratory of Urban and Rural Ecological Environment, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants of Ministry of Education, School of Landscape Architecture, Beijing Forestry University, Beijing 100083, China.
Shandong Institute of Pomology, Shandong Academy of Agricultural Sciences, Tai'an 271000, China.
Int J Mol Sci. 2022 Apr 29;23(9):4950. doi: 10.3390/ijms23094950.
In nature, many different factors cause plants to develop variegated leaves. To explore the mechanism of variegated leaf formation in , a mutant variety ('Jinyuyuan'), which was induced by ethylmethylsulfone, was selected, and its morphological structure, physiology, biochemistry, transcription and metabolism were analysed. According to differences in colour values, the colours were divided into two regions: a green region and a yellow-green region. The chlorophyll content of the two regions was significantly different. Moreover, the yellow-green regions of the leaves were significantly thinner than the green regions. The chloroplast ultrastructure in the yellow-green region revealed small chloroplasts, large vacuoles, small starch grains, obviously increased numbers of osmophilic grains, loose lamellae of the inner capsule and thin lamellae. Moreover, the yellow-green region was accompanied by oxidative stress, and the activity of the oxidative phosphorylation pathway related to oxidative activity in the transcriptome showed an upward trend. Vitamin B6 and proline contents also increased, indicating that the antioxidant activity of cells in the yellow-green region increased. Transcriptomic and metabolomic analysis showed that the differentially expressed genes (DEGs) related to chlorophyll synthesis and metabolism led to a decrease in the photosynthesis and then a decrease in the assimilation ability and contents of sucrose, starch and other assimilates. Amino acid synthesis and metabolism, lipid synthesis and the activity of metabolic pathways were obviously downregulated, and the contents of differentially accumulated metabolites associated with amino acids and lipids were also reduced. At the same time, 31 out of 32 DEGs involved in the flavonoid synthesis pathway were downregulated, which affected leaf colour. We hypothesized that the variegated leaves of 'Jinyuyuan' are caused by transcriptional and post-transcriptional regulation. Mutations in pigment and flavonoid synthesis pathway genes and transcription factor genes directly affect both pigment and flavonoid synthesis and degradation rate, which in turn affect carbon assimilation, carbon fixation, related protein synthesis and enzyme activity, lipid synthesis and degradation and the activity of other metabolic pathways, eventually leading to the formation of different colour regions.
在自然界中，许多不同的因素导致植物产生斑驳的叶子。为了探索 斑驳叶形成的机制，选择了由乙基甲磺酸诱导的突变体品种（'Jinyuyuan'），并对其形态结构、生理、生化、转录和代谢进行了分析。根据颜色值的差异，颜色分为两个区域：绿色区域和黄绿区域。两个区域的叶绿素含量有显著差异。此外，叶片的黄绿区域明显比绿色区域薄。在黄绿区域的叶绿体超微结构中，发现小叶绿体、大液泡、小淀粉粒、明显增加的嗜盐颗粒、内囊疏松的薄片和薄的薄片。此外，黄绿区域伴随着氧化应激，与氧化活性相关的氧化磷酸化途径的活性在转录组中呈上升趋势。维生素 B6 和脯氨酸含量也增加，表明黄绿区域细胞的抗氧化活性增加。转录组和代谢组分析表明，与叶绿素合成和代谢相关的差异表达基因（DEGs）导致光合作用减少，进而导致同化能力和蔗糖、淀粉等同化产物的含量降低。氨基酸合成和代谢、脂质合成和代谢途径的活性明显下调，与氨基酸和脂质相关的差异积累代谢物的含量也降低。同时，黄酮类化合物合成途径中的 31 个 DEGs 下调，影响了叶片颜色。我们假设 'Jinyuyuan' 的斑驳叶片是由转录和转录后调控引起的。色素和类黄酮合成途径基因和转录因子基因突变直接影响色素和类黄酮的合成和降解速率，进而影响碳同化、碳固定、相关蛋白合成和酶活性、脂质合成和降解以及其他代谢途径的活性，最终导致不同颜色区域的形成。
