Growth asymmetry precedes differential auxin response during apical hook initiation in Arabidopsis

Yang Peng, Dan Zhang, Yuping Qiu, Zhina Xiao, Yusi Ji, Wenyang Li, Yiji Xia, Yichuan Wang*, Hongwei Guo*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

12 Citations (Scopus)


The development of a hook-like structure at the apical part of the soil-emerging organs has fascinated botanists for centuries, but how it is initiated remains unclear. Here, we demonstrate with high-throughput infrared imaging and 2-D clinostat treatment that, when gravity-induced root bending is absent, apical hook formation still takes place. In such scenarios, hook formation begins with a de novo growth asymmetry at the apical part of a straightly elongating hypocotyl. Remarkably, such de novo asymmetric growth, but not the following hook enlargement, precedes the establishment of a detectable auxin response asymmetry, and is largely independent of auxin biosynthesis, transport and signaling. Moreover, we found that functional cortical microtubule array is essential for the following enlargement of hook curvature. When microtubule array was disrupted by oryzalin, the polar localization of PIN proteins and the formation of an auxin maximum became impaired at the to-be-hook region. Taken together, we propose a more comprehensive model for apical hook initiation, in which the microtubule-dependent polar localization of PINs may mediate the instruction of growth asymmetry that is either stochastically taking place, induced by gravitropic response, or both, to generate a significant auxin gradient that drives the full development of the apical hook.

Original languageEnglish
Pages (from-to)5-22
Number of pages18
JournalJournal of Integrative Plant Biology
Issue number1
Early online date16 Nov 2021
Publication statusPublished - Jan 2022

Scopus Subject Areas

  • Biochemistry
  • Biochemistry, Genetics and Molecular Biology(all)
  • Plant Science


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