@article{6262,
  abstract     = {Gravitropism is an adaptive response that orients plant growth parallel to the gravity vector. Asymmetric
distribution of the phytohormone auxin is a necessary prerequisite to the tropic bending both in roots and
shoots. During hypocotyl gravitropic response, the PIN3 auxin transporter polarizes within gravity-sensing
cells to redirect intercellular auxin fluxes. First gravity-induced PIN3 polarization to the bottom cell mem-
branes leads to the auxin accumulation at the lower side of the organ, initiating bending and, later, auxin
feedback-mediated repolarization restores symmetric auxin distribution to terminate bending. Here, we per-
formed a forward genetic screen to identify regulators of both PIN3 polarization events during gravitropic
response. We searched for mutants with defective PIN3 polarizations based on easy-to-score morphological
outputs of decreased or increased gravity-induced hypocotyl bending. We identified the number of
hypocotyl reduced bending (hrb) and hypocotyl hyperbending (hhb) mutants, revealing that reduced bending corre-
lated typically with defective gravity-induced PIN3 relocation whereas all analyzed hhb mutants showed
defects in the second, auxin-mediated PIN3 relocation. Next-generation sequencing-aided mutation map-
ping identified several candidate genes, including SCARECROW and ACTIN2, revealing roles of endodermis
specification and actin cytoskeleton in the respective gravity- and auxin-induced PIN polarization events.
The hypocotyl gravitropism screen thus promises to provide novel insights into mechanisms underlying cell
polarity and plant adaptive development.},
  author       = {Rakusová, Hana and Han, Huibin and Valošek, Petr and Friml, Jiří},
  issn         = {1365-313x},
  journal      = {The Plant Journal},
  number       = {6},
  pages        = {1048--1059},
  publisher    = {Wiley},
  title        = {{Genetic screen for factors mediating PIN polarization in gravistimulated Arabidopsis thaliana hypocotyls}},
  doi          = {10.1111/tpj.14301},
  volume       = {98},
  year         = {2019},
}