Genetic screen for factors mediating PIN polarization in gravistimulated Arabidopsis thaliana hypocotyls Rakusová, Hana Han, Huibin Valošek, Petr Friml, Jiří ; https://orcid.org/0000-0002-8302-7596 ddc:580 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. Wiley 2019 info:eu-repo/semantics/article doc-type:Article Article http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/6262 https://research-explorer.ista.ac.at/download/6262/6304 Rakusová H, Han H, Valošek P, Friml J. Genetic screen for factors mediating PIN polarization in gravistimulated Arabidopsis thaliana hypocotyls. <i>The Plant Journal</i>. 2019;98(6):1048-1059. doi:<a href="https://doi.org/10.1111/tpj.14301">10.1111/tpj.14301</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1111/tpj.14301 info:eu-repo/semantics/altIdentifier/issn/0960-7412 info:eu-repo/semantics/altIdentifier/e-issn/1365-313x info:eu-repo/semantics/altIdentifier/wos/000473644100008 info:eu-repo/semantics/altIdentifier/pmid/30821050 https://creativecommons.org/licenses/by/4.0/ info:eu-repo/semantics/openAccess