竹鞭是散生竹的主茎，对竹子地下茎的研究对竹子生长发育意义重大。利用多学科方法，综合解析竹子地下茎节间生长的解剖学变化及其转录组特征。

采用形态学观察结合石蜡切片、扫描电镜等方法观察矢竹(Pseudosasa japonica)地下茎生长过程中的形态学变化及解剖结构特征；并利用转录组测序结合生物信息学分析比较不同生长阶段节间转录组特征；差异表达基因利用MapMan软件进行可视化分析。

矢竹地下茎的生长主要由竹鞭前端约14个处于不同生长发育阶段的节间生长引起。解剖学分析进一步表明，长度小于0.4 cm的节间细胞具有较强的分裂能力；而1.0 cm长节间主要以细胞伸长生长为主。同时1.0 cm长节间基本组织细胞已具有显著的长、短细胞之分，且其导管细胞、纤维细胞等维管组织细胞较0.4 cm长节间的同类细胞在长度上更长，发育更为成熟。除此之外，相比于0.4 cm长节间，1.0 cm长节间髓组织已明显破裂，并初步形成了髓腔。通过比较0.4 cm长节间与1.0 cm长节间转录组图谱发现，差异表达基因从0.4 cm长节间中以细胞分裂与初生代谢基因表达为主，向1.0 cm长节间中以细胞壁合成、次生代谢基因表达为主进行转变。同时，1.0 cm长节间与细胞程序性死亡相关基因如乙烯信号通路及活性氧爆发相关基因也呈显著上调表达。

矢竹地下茎节间在生长过程中存在一个明显的由细胞分裂为主向细胞伸长生长为主的转变。同时，在节间生长中还伴随一些发育过程的转变，如长、短细胞的发育，髓腔的形成。而这些过程的转变可能与细胞生长及细胞程序性死亡等相关基因的上调表达有关。

The underground rhizome is the main stem of the running bamboo forest. However, little is known about its development, such as its elongation that is important for bamboo forest spread. In the present study, we aim to explore the cellular and transcriptomic features of rhizome internode elongation of Pseudosasa japonicas.

Cellular observation was completed via paraffin sectioning, analysis of the transcriptomic profile via next?generation sequencing technology, and visualization, as well as enrichment analysis of differentially expressed genes, via MapMan.

Through the morphological analysis of P. japonica’s rhizome elongation, we discovered that the elongation was directly promoted by the growth of -14 young internodes in the rhizome shoot. The anatomical analysis results further revealed that internodes with lengths lower than 0.4 cm had strong cell division ability, and distinctive cell elongation was found in a 1.0 cm long internode. Long and short parenchymal cells were apparent in the 1.0 cm internode and its vascular tissue such as vessel cells and fiber cells were much longer and more developed than in the 0.4 cm internode. It was also observed that pith tissue broke to form the pith cavity in the 1.0 cm internode. The RNA?Seq analysis between 0.4 and 1.0 cm internodes revealed a transition of transcriptomic activities. This included a transition from cell division and basic cellular metabolism in the 0.4 cm internode to active cell growth processes such as cell wall biosynthesis and secondary metabolism, and in the 1.0 cm internode to Programmed Cell Death processes such as ethylene signal pathways and (reactive oxygen species, ROS) burst genes.

There is a transition of cell growth processes from cell division to cell elongation during P. japonica’s rhizome internode elongation. Additionally, developmental events such as pith cavity formation exist in the 1.0 cm internode, which might be due to upregulation of genes related to cell growth and Programmed Cell Death.