Transcriptome Analysis Revealed Behavior Complexity of Senescence Responses in Himalayan Tree Species Ulmus wallichiana

The Himalayas present a highly contrasting environment for the organisms that inhabit it, with summer and winter being the most disparate seasons. As winter approaches, the temperature drops, and deciduous plants, such as Ulmus wallichiana Planch., undergo senescence. In this study, we used the RNA-seq approach to generate a de novo transcriptome assembly of U. wallichiana , consisting of 300,067 unigenes. We investigated the differential expression pattern of these unigenes under changing climatic conditions, with a focus on the contrast between winter and summer. We observed that 2746 unigenes were differentially expressed, with a fold change of ≥ 2 and an FDR-adjusted p -value of ≤ 0.001. Among these unigenes, 37 were found to be related to senescence. We also identified nine DREB unigenes in the U. wallichiana transcriptome, which exhibited more or less contrasting patterns between summer and winter. These DREB unigenes may play an important role in regulating the plant’s tolerance to cold and/or drought stress. Our findings shed light on the complex and dynamic process of transcriptomic reprogramming that enables U. wallichiana to cope with seasonal changes. Furthermore, this study highlights the urgent need for further research on U. wallichiana , as this endangered plant species remains largely unexplored at the genomic level.