Moso bamboo (Phyllostachys edulis), a high-value bamboo used to produce food (young shoots), building, and industrial goods. To explore key candidate genes regulating signal transduction and metabolic processes during the initiation of stem elongation in moso bamboo, a transcriptome analysis of the shoots during three successive early elongation stages was performed. From cluster and differential expression analyses, 2984 differentially expressed genes (DEGs) were selected for an enrichment analysis. The DEGs were significantly enriched in the plant hormone signal transduction, sugar and starch metabolism, and energy metabolism pathways.Consequently, the DEG expression patterns of these pathways were analyzed, and the plant endogenous hormone and carbon metabolite (including sucrose, total soluble sugar, and starch) contents for each growth stage, of the shoot, were determined.The cytokinin-signaling pathway was continuously active in the three successive elongation stages, in which several cytokinin-signaling genes played indispensable roles. Additionally, many key DEGs regulating sugar, starch metabolism, and energy conversion, which are actively involved in energy production and substrate synthesis during the continuous growth of the shoots, were found. In summary, our study lays a foundation for understanding the mechanisms of moso bamboo growth and provides useful gene resources for breeding through genetic engineering. | INTRODUCTIONAt present, with a growing focus on the environment, the exploration of renewable resources to produce fuel, chemicals, and materials is becoming increasingly important (Matsakas et al., 2019). Thus, the development of fast-growing and high-yield wood resources for energy, chemical, and food products is vital, especially as agricultural and forestry biomass resources (FitzPatrick et al., 2010;Zhang et al., 2011). Moso bamboo (Phyllostachys edulis) is highly valuable because of its use food production (juvenile shoots), as building material, and the production of industrial goods. Additionally, it is a highly important and popular bamboo species, having great ecological, economic, and cultural values worldwide owing to its characteristics of easy reproduction, rapid growth, and high productivity (Peng et al., 2010). Understanding the characteristics of its early growth and development will be conducive in order to be able to utilize the moso bamboo resources better.Owing to its extraordinarily rapid growth, moso bamboo has been studied extensively. The rapid growth is largely achieved through cell division and the elongation of the intercalary meristem at the basal

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Mitogen‐activated protein kinases (MAPKs) play important roles in plant growth and development, as well as hormone and stress responses by signaling to eukaryotic cells, through MAPK cascade, the presence of various cues; thereby, regulating various responses. The MAPK cascade consists mainly of three gene families, MAPK, MAPKK, and MAPKKK, which activate downstream signaling pathways through sequential phosphorylation. Although the MAPK cascade gene family has been reported in several species, there is a lack of comprehensive analysis in poplar. We identified 21 MAPK genes, 11 MAPKK genes, and 104 MAPKKK genes in Populus trichocarpa. The phylogenetic classification was supported by conservative motif, gene structure and motif analysis. Whole genome duplication has an important role in the expansion of MAPK cascade genes. Analysis of promoter cis‐elements and expression profiles indicates that MAPK cascade genes have important roles in plant growth and development, abiotic and biotic stresses, and phytohormone response. Expression profiling revealed a significant upregulation of PtMAPK3‐1 expression in response to drought, salt and disease stresses. Poplar transiently overexpressing PtMAPK3‐1 and treated with methyl jasmonic acid (MeJA) had higher catalase and peroxidase levels than non‐overexpressing poplar. This work represents the first complete inventory of the MAPK cascade in P. trichocarpa, which reveals that PtMAPK3‐1 is induced by the MeJA hormone and participates in the MeJA‐induced enhancement of the antioxidant enzyme system.

As a model tree species, poplar (Populus L.) has important economic and ecological value. Here, we constructed the GEPSdb (Gene Expression Database of Poplar under Stress; http://gepsdb.ahau-edu.cn/), which is an integrated database of poplar gene expression profiles derived from RNA‐seq and microarray library data. This database provides a comprehensive collection of gene expression data from poplar exposed to 14 types of environmental stress from 11 high‐quality RNA‐seq experiments and 51 microarray libraries. The GEPSdb includes 56 genes from previous literature that have been examined in poplar and functionally verified. By incorporating data from numerous expression analyses, GEPSdb provides a user‐friendly web interface for querying, browsing, and visualizing the expression profiles of related genes. Consequently, GEPSdb can be used to link transcription data with phenotypes and can enhance our understanding of important biological processes and mechanisms underlying complex agronomic traits in poplar.

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