Formation of the apical hook in etiolated dicot seedlings results from differential growth in the hypocotyl apex and is tightly controlled by environmental cues and hormones, among which auxin and gibberellins (GAs) play an important role. Cell expansion is tightly regulated by the cell wall, but whether and how feedback from this structure contributes to hook development are still unclear. Here, we show that etiolated seedlings of the Arabidopsis (Arabidopsis thaliana) quasimodo2-1 (qua2) mutant, defective in pectin biosynthesis, display severe defects in apical hook formation and maintenance, accompanied by loss of asymmetric auxin maxima and differential cell expansion. Moreover, qua2 seedlings show reduced expression of HOOKLESS1 (HLS1) and PHYTOCHROME INTERACTING FACTOR4 (PIF4), which are positive regulators of hook formation. Treatment of wild-type seedlings with the cellulose inhibitor isoxaben (isx) also prevents hook development and represses HLS1 and PIF4 expression. Exogenous GAs, loss of DELLA proteins, or HLS1 overexpression partially restore hook development in qua2 and isx-treated seedlings. Interestingly, increased agar concentration in the medium restores, both in qua2 and isx-treated seedlings, hook formation, asymmetric auxin maxima, and PIF4 and HLS1 expression. Analyses of plants expressing a Förster resonance energy transfer-based GA sensor indicate that isx reduces accumulation of GAs in the apical hook region in a turgor-dependent manner. Lack of the cell wall integrity sensor THESEUS 1, which modulates turgor loss point, restores hook formation in qua2 and isx-treated seedlings. We propose that turgor-dependent signals link changes in cell wall integrity to the PIF4-HLS1 signaling module to control differential cell elongation during hook formation.

• MeSH
• Arabidopsis * genetika   růst a vývoj   metabolismus   MeSH
• benzamidy MeSH
• buněčná stěna * metabolismus   MeSH
• gibereliny metabolismus   MeSH
• hypokotyl růst a vývoj   genetika   metabolismus   MeSH
• kyseliny indoloctové * metabolismus   MeSH
• mutace genetika   MeSH
• pektiny metabolismus   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• regulace genové exprese u rostlin * MeSH
• semenáček * genetika   růst a vývoj   metabolismus   MeSH
• transkripční faktory bHLH * metabolismus   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• benzamidy MeSH
• gibereliny MeSH
• isoxaben MeSH Prohlížeč
• kyseliny indoloctové * MeSH
• pektiny MeSH
• PIF4 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku * MeSH
• transkripční faktory bHLH * MeSH