Endogenous Auxin is Required but Supraoptimal for Rapid Growth of Rice (Oryza sativa L.) Seminal Roots, and Auxin Inhibition of Rice Seminal Root Growth is Not Caused by Ethylene

Yin, Changxi; Wu, Quanrong; Zeng, Hanlai; Xia, Kai; Jian, Xu; Rongwei, Li

doi:10.1007/s00344-010-9162-z

Cited by 31 publications

(21 citation statements)

References 63 publications

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“…As expected, in Arabidopsis this root growth reduction is accompanied by gradually decreased free auxin levels [17]. Thus, the most parsimonious explanation for the Bdtar2l phenotype is that auxin levels might normally be supra-optimal for cell elongation in Brachypodium, similar to what has been proposed for rice [25]. To our surprise then, we found that free auxin levels are elevated rather than reduced in Bdtar2l seminal roots (Fig.…”

Section: Resultssupporting

confidence: 85%

“…Compared to those mutants, the enhanced root elongation phenotype of Bdtar2l mutants is unusual. Our initial interpretation was therefore that auxin levels are supra-optimal for cell elongation in the Brachypodium seminal root, as has been suggested for seminal root growth in rice [25]. However, repeated independent measurements of multiple samples clearly indicated that auxin levels are increased rather than decreased in Bdtar2l mutant roots.…”

Section: Discussionmentioning

confidence: 65%

“…This finding also illustrates the dosage-dependent action of auxin, because although auxin and its perception are essential for root formation and growth, excess auxin application, biosynthesis or signaling are eventually inhibitory [22]–[24]. Indeed, it has been suggested that depending on the species, auxin levels might be supra-optimal for root growth [25].…”

Section: Introductionmentioning

confidence: 66%

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Disturbed Local Auxin Homeostasis Enhances Cellular Anisotropy and Reveals Alternative Wiring of Auxin-ethylene Crosstalk in Brachypodium distachyon Seminal Roots

et al. 2013

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Observations gained from model organisms are essential, yet it remains unclear to which degree they are applicable to distant relatives. For example, in the dicotyledon Arabidopsis thaliana (Arabidopsis), auxin biosynthesis via indole-3-pyruvic acid (IPA) is essential for root development and requires redundant TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 (TAA1) and TAA1-RELATED (TAR) genes. A promoter T-DNA insertion in the monocotyledon Brachypodium distachyon (Brachypodium) TAR2-LIKE gene (BdTAR2L) severely down-regulates expression, suggesting reduced tryptophan aminotransferase activity in this mutant, which thus represents a hypomorphic Bdtar2l allele (Bdtar2lhypo). Counterintuitive however, Bdtar2lhypo mutants display dramatically elongated seminal roots because of enhanced cell elongation. This phenotype is also observed in another, stronger Bdtar2l allele and can be mimicked by treating wild type with L-kynerunine, a specific TAA1/TAR inhibitor. Surprisingly, L-kynerunine-treated as well as Bdtar2l roots display elevated rather than reduced auxin levels. This does not appear to result from compensation by alternative auxin biosynthesis pathways. Rather, expression of YUCCA genes, which are rate-limiting for conversion of IPA to auxin, is increased in Bdtar2l mutants. Consistent with suppression of Bdtar2lhypo root phenotypes upon application of the ethylene precursor 1-aminocyclopropane-1-carboxylic-acid (ACC), BdYUCCA genes are down-regulated upon ACC treatment. Moreover, they are up-regulated in a downstream ethylene-signaling component homolog mutant, Bd ethylene insensitive 2-like 1, which also displays a Bdtar2l root phenotype. In summary, Bdtar2l phenotypes contrast with gradually reduced root growth and auxin levels described for Arabidopsis taa1/tar mutants. This could be explained if in Brachypodium, ethylene inhibits the rate-limiting step of auxin biosynthesis in an IPA-dependent manner to confer auxin levels that are sub-optimal for root cell elongation, as suggested by our observations. Thus, our results reveal a delicate homeostasis of local auxin and ethylene activity to control cell elongation in Brachypodium roots and suggest alternative wiring of auxin-ethylene crosstalk as compared to Arabidopsis.

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Section: Resultssupporting

confidence: 85%

Section: Discussionmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 66%

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Disturbed Local Auxin Homeostasis Enhances Cellular Anisotropy and Reveals Alternative Wiring of Auxin-ethylene Crosstalk in Brachypodium distachyon Seminal Roots

et al. 2013

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“…0.01 µM (Zn-deficient -Zn 0.00024 ppm) and 2.0 µM (Zn-sufficient/control -Zn 0.051 ppm). In addition, 2.5 µM TIBA (polar auxin transport inhibitor) applied to nutrient media with reapplication every 3 days (Yin et al 2011). The pH (6.0) of the nutrient solution was strictly maintained by HCl or KOH and seedlings were grown in 2 L container of aerated solution at 25°C.…”

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

Auxin signaling is closely associated with Zn-efficiency in rice (Oryza sativa L.)

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Islam

Sarkar

et al. 2016

Journal of Plant Interactions

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This study elucidates the involvement of auxin with Zn-efficiency (ZE) in Zn-efficient rice var. Pokkali. Pokkali showed no significant decrease in morpho-physiological features, electrolyte leakage and total soluble proteins due to Zn deficiency as compared with Zn-sufficient seedlings. However, auxin inhibitor under Zn deficiency severely affected these characteristics, suggesting that ZE is associated with auxin signaling in rice. Results further revealed significant decreases in the expression of Zn transporter genes (OsIRT1, OsZIP4 and OsZIP1), OsDMAS1 (deoxymugeneic acid synthase) and phytochelatin in roots due to auxin inhibitor. It implies that auxin signaling may trigger Zn uptake, transport and chelation in rice seedlings to withstand Zn-deficiency. Further, significant reduction of major S-metabolites (cysteine, methionine, glutathione) and antioxidant enzymes (superoxide dismutase and glutathione reductase) along with increased H 2 O 2 content, due to auxin inhibitor under Zn deficiency compared with controls. Taken together, these findings reveal that mechanisms associated with ZE in Pokkali are dependent on auxin signaling. ARTICLE HISTORY

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“…Once seedlings were transferred to the solution culture, 2.5 μM TIBA (polar auxin transport inhibitor) mixed with lanolin was applied to stem with reapplication in every 2 days (Yin et al, 2011). Lanolin was also used to the plants not treated with an inhibitor to nullify the effect (if any) of lanolin itself.…”

Section: Methodsmentioning

confidence: 99%

Regulation of Phytosiderophore Release and Antioxidant Defense in Roots Driven by Shoot-Based Auxin Signaling Confers Tolerance to Excess Iron in Wheat

et al. 2016

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Iron (Fe) is essential but harmful for plants at toxic level. However, how wheat plants tolerate excess Fe remains vague. This study aims at elucidating the mechanisms underlying tolerance to excess Fe in wheat. Higher Fe concentration caused morpho-physiological retardation in BR 26 (sensitive) but not in BR 27 (tolerant). Phytosiderophore and 2-deoxymugineic acid showed no changes in BR 27 but significantly increased in BR 26 due to excess Fe. Further, expression of TaSAMS. TaDMAS1, and TaYSL15 significantly downregulated in BR 27 roots, while these were upregulated in BR 26 under excess Fe. It confirms that inhibition of phytosiderophore directs less Fe accumulation in BR 27. However, phytochelatin and expression of TaPCS1 and TaMT1 showed no significant induction in response to excess Fe. Furthermore, excess Fe showed increased catalase, peroxidase, and glutathione reductase activities along with glutathione, cysteine, and proline accumulation in roots in BR 27. Interestingly, BR 27 self-grafts and plants having BR 26 rootstock attached to BR 27 scion had no Fe-toxicity induced adverse effect on morphology but showed BR 27 type expressions, confirming that shoot-derived signal triggering Fe-toxicity tolerance in roots. Finally, auxin inhibitor applied with higher Fe concentration caused a significant decline in morpho-physiological parameters along with increased TaSAMS and TaDMAS1 expression in roots of BR 27, revealing the involvement of auxin signaling in response to excess Fe. These findings propose that tolerance to excess Fe in wheat is attributed to the regulation of phytosiderophore limiting Fe acquisition along with increased antioxidant defense in roots driven by shoot-derived auxin signaling.

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Endogenous Auxin is Required but Supraoptimal for Rapid Growth of Rice (Oryza sativa L.) Seminal Roots, and Auxin Inhibition of Rice Seminal Root Growth is Not Caused by Ethylene

Cited by 31 publications

References 63 publications

Disturbed Local Auxin Homeostasis Enhances Cellular Anisotropy and Reveals Alternative Wiring of Auxin-ethylene Crosstalk in Brachypodium distachyon Seminal Roots

Disturbed Local Auxin Homeostasis Enhances Cellular Anisotropy and Reveals Alternative Wiring of Auxin-ethylene Crosstalk in Brachypodium distachyon Seminal Roots

Auxin signaling is closely associated with Zn-efficiency in rice (Oryza sativa L.)

Regulation of Phytosiderophore Release and Antioxidant Defense in Roots Driven by Shoot-Based Auxin Signaling Confers Tolerance to Excess Iron in Wheat

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