The metabolism of phenylalanine plays a central role in the channeling of carbon from photosynthesis to the
biosynthesis of phenylpropanoids duringwood formation. This crucial pathway is finely regulated primarily at the
transcriptional level by MYB and NAC transcription factors. In Arabidopsis, poplar and eucalyptus, the transcriptional
network controlling secondary cell wall involves NAC-domain regulators operating upstream Myb transcription
factors, but in conifers functional evidence had only been obtained for MYBs. We showed that PpMYB8 is a regulator
of phenylpropanoid metabolism and lignin synthesis genes (Craven-Bartle et al. 2013) and three NAC genes PpNAC1,
PpNAC30 and PpNAC31 were associated to vascular development in maritime pine (Pascual et al. 2015). Of all of
them, PpNAC1 is expressed in the secondary xylem and compression wood of adult trees and phylogenetic analysis
classified PpNAC1 as potential candidates to be involved in a transcriptional regulatory network controlling
phenylalanine metabolism in maritime pine. This NAC transcription factor has been thoroughly characterized and its
role upstream the transcriptional network involving Mybs TFs will be discussed. Understanding the molecular
switches controlling wood formation is of paramount importance for fundamental tree biology and has important
implications in tree biotechnology.
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