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