Multiple Facets of Arabidopsis Seedling Development Require * Indole-3-Butyric Acid-Derived Auxin

Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA.
The Plant Cell (Impact Factor: 9.34). 03/2011; 23(3):984-99. DOI: 10.1105/tpc.111.083071
Source: PubMed


Levels of auxin, which regulates both cell division and cell elongation in plant development, are controlled by synthesis, inactivation, transport, and the use of storage forms. However, the specific contributions of various inputs to the active auxin pool are not well understood. One auxin precursor is indole-3-butyric acid (IBA), which undergoes peroxisomal β-oxidation to release free indole-3-acetic acid (IAA). We identified ENOYL-COA HYDRATASE2 (ECH2) as an enzyme required for IBA response. Combining the ech2 mutant with previously identified iba response mutants resulted in enhanced IBA resistance, diverse auxin-related developmental defects, decreased auxin-responsive reporter activity in both untreated and auxin-treated seedlings, and decreased free IAA levels. The decreased auxin levels and responsiveness, along with the associated developmental defects, uncover previously unappreciated roles for IBA-derived IAA during seedling development, establish IBA as an important auxin precursor, and suggest that IBA-to-IAA conversion contributes to the positive feedback that maintains root auxin levels.

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    • "Similarly, the conversion of IBA to IAA (the principal form of auxin) occurs in peroxisomes. The predicted pathway for IBA metabolism also parallels with β-oxidation of fatty acids (Strader et al., 2011). Since, most of developmental changes as well as abiotic/biotic stresses are associated with modulation of cellular energetics and hormone levels, underlying signaling are either directly or indirectly integrated with redox-regulatory metabolic network. "

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    • "short root hair (Spiess et al., 2014) mes17 ill2 iar3, mes17 ibr3 not so severe shortroot hair phenotype (Spiess et al., 2014) Iar4 short root hairs. Rescued by oxYUCCA1 (Quint et al., 2009) YUCCA1ox long root hair phenotype (Zhao et al., 2001yucca1 yucca2 yucca4 yucca6 hairy root hair phenotype (Chen and Xiong, 2009)IBA-transport cdcg36(pen3,pdr8) long root hairs (Strader et al., 2011)IAA-perception tir1, tir1 afb2 afb3 short root hairs (Dharmasiri et al., 2005) pEXP7a:TIR1 longer root hairs (Ganguly et al., 2010) "
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    • "Additionally, while the frequency of the oscillation in DR5 expression was unperturbed, the amplitude of the oscillation was diminished. Following disruption of auxin biosynthesis in roots with mutations in[5], similar alterations in the amplitude of the DR5 oscillation were observed. Based on the reduction in prebranch site and LR numbers observed in roots with decreased amplitude of the DR5 oscillation, the authors conclude that both aspects of the oscillation, frequency and amplitude, are necessary for LR pre-patterning. "
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