Transcriptome analysis of Ulmus pumila ‘Jinye’ responses to different shading involved in chlorophyll metabolism

A variety of colorful mutations exist in nature. However, shade stress will affect the color of ornamental plants. Ulmus pumila ‘Jinye’ is a cultivated species of elm with a yellow leaf color, which will become green under shade stress. In this paper, ‘Jinye’ samples were treated with different degrees of shade by using shading net to investigate the mechanism of greening of the yellow leaves through phenotype observation and high-throughput sequencing. The height of plants rose in slight shade stress then fell in heavy shade stress. The content of chlorophyll and carotenoid increased with the increase of shade degree, and the leaf size increased as well. On the other hand, the net photosynthesis capacity declined. About 32.17 Gb of clean data were obtained after the completion of sequencing. A total of 33,023 unigenes with annotated information were obtained after comparing ‘Jinye’ with other species. The number of differentially expressed genes increased, and the proportion of upregulated genes decreased with increasing shade. The differentially expressed gene (DEG) analysis showed that the porphyrin and chlorophyll metabolism of Ulmus pumila ‘Jinye’ is affected by light. This may be related to genes associated with pigment synthesis. This first sequencing result of U. pumila will provide a basis for further research into this species.