Fig. 1. B. magnifica wood plasticity seen in stem cross-sections along the stem. (a ) A one-year-old plant grown with support. (b ) Secondary xylem formed by the regular cambium (RC) in older portions of the stem shows an abrupt transition from the self-supporting xylem (Ss) formed at the beginning of development to the lianescent xylem (L). The lianescent xylem is characterized by the presence of wide vessels, which are associated with narrow vessels and fewer fibers. (c ) The secondary xylem in younger portions of the stem is composed only of the self-supporting xylem (SS) formed by a high proportion of fibers and small vessels. It is possible to see the innermost position of the four regions of variant cambium (VC), responsible for the formation of phloem wedges characteristic of Bignonieae lianas, intercalated with the regular cambium (RC). Scales: (a) 33 cm, (b) 1 mm, (c), 500 µm. P: pith; Ph: secondary phloem.
Here we tested the hypothesis that liana attachment to physical supports promotes the formation of lianescent xylem by the cambium in older stem parts in the tendril climber Bignonia magnifica (Bignoniaceae). We propose that intraindividual plasticity in wood anatomy results from remodeling of the cambium and differentiating xylem transcriptome in these regions. By characterizing the anatomy of self-supporting and lianescent xylem, analyzing differential gene expression in the cambium and differentiating xylem, and providing a manually-curated comprehensive annotation, we propose a model for the molecular control of lianescent xylem differentiation. Our findings indicate distinct expression patterns between self-supporting and lianescent phases, with upregulation of cell division and cell wall-related transcripts in self-supporting xylem and a more intricate transcriptional regulation network, involving a diverse repertoire of transcription factors (TFs) and hormone-responsive genes.