Biphasic control of cell expansion by auxin coordinates etiolated seedling development

Minmin Du, Firas Bou Daher, Yuanyuan Liu, Andrew Steward, Molly Tillmann, Xiaoyue Zhang, Jeh Haur Wong, Hong Ren, Jerry D. Cohen, Chuanyou Li, William M. Gray

Research output: Contribution to journalArticlepeer-review

Abstract

Seedling emergence is critical for food security. It requires rapid hypocotyl elongation and apical hook formation, both of which are mediated by regulated cell expansion. How these events are coordinated in etiolated seedlings is unclear. Here, we show that biphasic control of cell expansion by the phytohormone auxin underlies this process. Shortly after germination, high auxin levels restrain elongation. This provides a temporal window for apical hook formation, involving a gravity-induced auxin maximum on the eventual concave side of the hook. This auxin maximum induces PP2C.D1 expression, leading to asymmetrical H+-ATPase activity across the hypocotyl that contributes to the differential cell elongation underlying hook development. Subsequently, auxin concentrations decline acropetally and switch from restraining to promoting elongation, thereby driving hypocotyl elongation. Our findings demonstrate how differential auxin concentrations throughout the hypocotyl coordinate etiolated development, leading to successful soil emergence.

Original languageEnglish (US)
Article numbereabj1570
JournalScience Advances
Volume8
Issue number2
DOIs
StatePublished - Jan 2022

Bibliographical note

Funding Information:
We thank E. Spalding for providing the seeds of atlazy mutants, J. Reed for the gift of axr2-1 seeds, H. Fukaki and M. Furutani for providing the arf7 arf19 pARF7::ARF7-GFP seeds, T. Kinoshita for providing α-AHA and α-pThr947 antisera, K.-i. Hayashi for providing auxinole, and C. Carter for providing his real-time PCR system for our qPCR experiments. We also thank the University Imaging Center for assistance with confocal microscopy. This work was supported by grants from the NIH (GM067203 to W.M.G.), the USDA National Institute of Food and Agriculture (2018-67013-27503 to J.D.C.), and the K.C. Wong Education Foundation (to C.L.).

Publisher Copyright:
© 2022 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).

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