Physiological and Anatomical Differences and Differentially Expressed Genes Reveal Yellow Leaf Coloration in Shumard Oak
2020
Xiaoyun Dong | Libin Huang | Qingsheng Chen | Yunzhou Lv | Hainan Sun | Zhenhai Liang
Shumard oak (Quercus shumardii Buckley) is a traditional foliage plant, but little is known about its regulatory mechanism of yellow leaf coloration. Here, the yellow leaf variety of Q. shumardii named &lsquo:Zhongshan Hongjincai&rsquo: (identified as &lsquo:ZH&rsquo: throughout this work) and a green leaf variety named &lsquo:Shumard oak No. 23&rsquo: (identified as &lsquo:SO&rsquo: throughout this work) were compared. &lsquo:ZH&rsquo: had lower chlorophyll content and higher carotenoid content: photosynthetic characteristics and chlorophyll fluorescence parameters were also lower. Moreover, the mesophyll cells of &lsquo:ZH&rsquo: showed reduced number of chloroplasts and some structural damage. In addition, transcriptomic analysis identified 39,962 differentially expressed genes, and their expression levels were randomly verified. Expressions of chlorophyll biosynthesis-related glumly-tRNA reductase gene and Mg-chelatase gene were decreased, while pheophorbide a oxygenase gene associated with chlorophyll degradation was up-regulated in &lsquo:ZH&rsquo:. Simultaneously, carotenoid isomerase gene, z-carotene desaturase gene, violaxanthin de-epoxidase gene and zeaxanthin epoxidase gene involved in carotenoid biosynthesis were up-regulated in &lsquo:ZH&rsquo:. These gene expression changes were accompanied by decreased chlorophyll content and enhanced carotenoid accumulation in &lsquo:ZH&rsquo:. Consequently, changes in the ratio of carotenoids to chlorophyll could be driving the yellow leaf coloration in Q. shumardii.
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