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.