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Tabeta H, Watanabe S, Fukuda K, Gunji S, Asaoka M, Hirai MY, Seo M, Tsukaya H, Ferjani A. An auxin signaling network translates low-sugar-state input into compensated cell enlargement in the fugu5 cotyledon. PLoS Genet 2021; 17:e1009674. [PMID: 34351899 PMCID: PMC8341479 DOI: 10.1371/journal.pgen.1009674] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 06/18/2021] [Indexed: 01/29/2023] Open
Abstract
In plants, the effective mobilization of seed nutrient reserves is crucial during germination and for seedling establishment. The Arabidopsis H+-PPase-loss-of-function fugu5 mutants exhibit a reduced number of cells in the cotyledons. This leads to enhanced post-mitotic cell expansion, also known as compensated cell enlargement (CCE). While decreased cell numbers have been ascribed to reduced gluconeogenesis from triacylglycerol, the molecular mechanisms underlying CCE remain ill-known. Given the role of indole 3-butyric acid (IBA) in cotyledon development, and because CCE in fugu5 is specifically and completely cancelled by ech2, which shows defective IBA-to-indoleacetic acid (IAA) conversion, IBA has emerged as a potential regulator of CCE. Here, to further illuminate the regulatory role of IBA in CCE, we used a series of high-order mutants that harbored a specific defect in IBA-to-IAA conversion, IBA efflux, IAA signaling, or vacuolar type H+-ATPase (V-ATPase) activity and analyzed the genetic interaction with fugu5-1. We found that while CCE in fugu5 was promoted by IBA, defects in IBA-to-IAA conversion, IAA response, or the V-ATPase activity alone cancelled CCE. Consistently, endogenous IAA in fugu5 reached a level 2.2-fold higher than the WT in 1-week-old seedlings. Finally, the above findings were validated in icl-2, mls-2, pck1-2 and ibr10 mutants, in which CCE was triggered by low sugar contents. This provides a scenario in which following seed germination, the low-sugar-state triggers IAA synthesis, leading to CCE through the activation of the V-ATPase. These findings illustrate how fine-tuning cell and organ size regulation depend on interplays between metabolism and IAA levels in plants.
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Affiliation(s)
- Hiromitsu Tabeta
- Department of Biology, Tokyo Gakugei University, Koganei-shi, Tokyo, Japan
- RIKEN Center for Sustainable Resource Science, Yokohama, Japan
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo, Japan
| | | | - Keita Fukuda
- Department of Biology, Tokyo Gakugei University, Koganei-shi, Tokyo, Japan
| | - Shizuka Gunji
- Department of Biology, Tokyo Gakugei University, Koganei-shi, Tokyo, Japan
| | - Mariko Asaoka
- Department of Biology, Tokyo Gakugei University, Koganei-shi, Tokyo, Japan
- Laboratoire de Reproduction et Développement des Plantes, Université de Lyon, UCB Lyon 1, ENS de Lyon, INRA, CNRS, Lyon, France
| | | | - Mitsunori Seo
- RIKEN Center for Sustainable Resource Science, Yokohama, Japan
| | - Hirokazu Tsukaya
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Ali Ferjani
- Department of Biology, Tokyo Gakugei University, Koganei-shi, Tokyo, Japan
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