Liana Attachment to Supports Leads to Profound Changes in Xylem Anatomy and Cambium and Differentiating Xylem Transcriptional Profile

Wood serves crucial functions in plants, yet our understanding of the molecular regulation governing the composition, arrangement, and dimensions of its cells remains limited. The abrupt change in wood anatomy of lianas represents an excellent model to address the underlying mechanism, although consistent triggering factors for this process remain uncertain. In this study we examined how physical support attachment impacts the development of lianescent xylem anatomy in Bignonia magnifica (Bignoniaceae), employing a comprehensive approach integrating detailed anatomical analysis with gene expression profiling of cambium and differentiating xylem. Our findings demonstrate that attachment to physical supports triggers the formation of lianescent xylem, leading to increased vessel size, range of vessel sizes, broader vessel distribution, reduced fiber content, and higher potential specific water conductivity. These shifts in wood anatomy coincide with the downregulation of genes associated with cell division and cell wall biosynthesis, and the upregulation of transcription factors (TFs), defense/cell death, and hormone-responsive genes in the lianescent xylem. Based on our results, we propose a model delineating the molecular control underlying the formation of lianescent xylem, revealing how the increased complexity of lianescent anatomy reflects a more intricate transcriptional regulatory network encompassing a more diverse repertoire of TFs and hormone-responsive genes.