Plants can re-orientate themselves according to the gravity vector. Response to gravistimulation is an essential mechanism whereby plants adapt to their environment. In angiosperm woody plants, reorientation of aerial parts involves the formation of tension wood which differs from normal wood by physiochemical and mechanical characteristics. Understanding the early processes leading to this wood formation is a challenging research question. Our working hypothesis is that molecular actors involved in gravisensing and/or graviresponse could be localized at a continuum between cytoskeleton-plasma membrane-cell wall as described in the gravitational pressure model (Baluška and Volkmann, 2011). A change in the gravity vector would modify plasma membrane-cell wall mechanical relations with a tension between this two cell compartments at the upper side of the cell and a compression at the lower side. At the interface of this continuum, wall associated kinases (WAKs) could be good candidates as sensors and/or actors of the cell mechanical deformation. Indeed, WAKs have an extracellular part that can bind to the pectins of the cell wall, a single transmembrane region and an intracellular kinase domain which could signal deformations between membrane and wall to the cytoplasm. Using in silico approaches, we showed in poplar the most expanded WAK family never identified to date with 175 members (Tocquard et al., 2014). We analyzed gene expression of the WAK family members in various organs and tissues of poplar tree and showed that WAKs were weakly expressed. Only 28 PtWAKs were expressed in the stem. One WAK is of particular interest showing differential expression after tilting of the poplar stem. The protein was localized in young xylem and bark cells devoid of amyloplasts. These data suggest that a WAK could be involved in the sensing/response to gravistimulation in a manner independent of the displacement of amyloplasts which is behind the starch-statolith hypothesis (Sack, 1997).