Auxin: Regulation, Action, and Interaction

Woodward, Andrew W.; Bartel, Bonnie

doi:10.1093/aob/mci083

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“…Our results, including localization, auxin transport as well as genetic and physiological analyses, showed that, although both PIN8 and PIN5 auxin transporters are localized at the ER, they can have antagonistic roles in regulating gametophyte and sporophyte development, cellular auxin homoeostasis and metabolism. PIN5 has been proposed to transport auxin intracellularly from the cytoplasm into the ER, where enzymes involved in IAA metabolism are compartmentalized 6 , thus reducing the auxin availability for the PM-based auxin efflux 24 . It is unclear how PIN8 localized to the same intracellular compartment, namely ER, can act antagonistically but it suggests more complex functional interaction between PIN proteins than anticipated so far.…”

Section: Discussionmentioning

confidence: 99%

“…T he plant hormone auxin has a crucial role in plant development [1][2][3][4][5][6] . On account of its differential distribution within plant tissues, it acts as a versatile coordinative signal mediating a multitude of processes, including female gametophyte patterning, embryogenesis, organogenesis, meristem activity, growth responses to environmental stimuli and others [7][8][9][10] .…”

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ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

et al. 2012

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Auxin is a key coordinative signal required for many aspects of plant development and its levels are controlled by auxin metabolism and intercellular auxin transport. Here we find that a member of PIn auxin transporter family, PIn8 is expressed in male gametophyte of Arabidopsis thaliana and has a crucial role in pollen development and functionality. Ectopic expression in sporophytic tissues establishes a role of PIn8 in regulating auxin homoeostasis and metabolism. PIn8 co-localizes with PIn5 to the endoplasmic reticulum (ER) where it acts as an auxin transporter. Genetic analyses reveal an antagonistic action of PIn5 and PIn8 in the regulation of intracellular auxin homoeostasis and gametophyte as well as sporophyte development. our results reveal a role of the auxin transport in male gametophyte development in which the distinct actions of ER-localized PIn transporters regulate cellular auxin homoeostasis and maintain the auxin levels optimal for pollen development and pollen tube growth.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

et al. 2012

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“…IAA is an auxin and some microarrays analyses have demonstrated up-regulation of NIT1 and NIT2 in response to IAN and NaCl treatment (Grsic et al, 1998;Jiang et al, 2007;Woodward and Bartel, 2005). Furthermore, NAC transcription factor also controls salinity stress via the auxin pathway (He et al, 2005;Park et al, 2011).…”

Section: Ataf2 Is Required For Full Induction Of Nit2 In Arabidopsismentioning

confidence: 99%

ATAF2, a NAC Transcription Factor, Binds to the Promoter and Regulates NIT2 Gene Expression Involved in Auxin Biosynthesis

Huh

Lee

Kim

et al. 2012

Molecules and Cells

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The transcription factor ATAF2, one of the plant specific NAC family genes, is known as repressor of pathogenesisrelated genes and responsive to the diverse defense-related hormones, pathogen infection, and wounding stress. Furthermore, it is important to consider that tryptophandependant IAA biosynthesis pathway can be activated by wounding and pathogen. We found that ATAF2pro::GUS reporter was induced upon indole-3-acetonitrile (IAN) treatments. And ataf2 mutant showed reduced sensitivity to IAN whereas 35S::ATAF2 plants showed hyper-sensitivity to IAN. IAN biosynthesis required nitrilase involved in the conversion of IAN to an auxin, indole-3-acetic acid (IAA). We found that the NIT2 gene was repressed in ataf2 knockout plants. Expression of both ATAF2 and NIT2 genes was induced by IAN treatment. Transgenic plants overexpressing ATAF2 showed up-regulated NIT2 expression. ATAF2 activated promoter of the NIT2 gene in Arabidopsis protoplasts. Electrophoretic mobility shift assay revealed that NIT2 promoter region from position -117 to -82 contains an ATAF2 binding site where an imperfect palindrome sequence was critical to the protein-DNA interaction. These findings indicate that ATAF2 regulates NIT2 gene expression via NIT2 promoter binding.

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“…The distribution of auxin depends on both auxin metabolism (biosynthesis, conjugation and degradation) [8][9][10] and cellular auxin transport [11][12][13][14][15] . We identified in silico a novel putative auxin transport facilitator family, called PIN-LIKES (PILS).…”

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A novel putative auxin carrier family regulates intracellular auxin homeostasis in plants

Barbez

Kubeš

Rolčı́k

et al. 2012

Nature

359

406

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The phytohormone auxin acts as a prominent signal, providing, by its local accumulation or depletion in selected cells, a spatial and temporal reference for changes in the developmental program [1][2][3][4][5][6][7] . The distribution of auxin depends on both auxin metabolism (biosynthesis, conjugation and degradation) [8][9][10] and cellular auxin transport [11][12][13][14][15] . We identified in silico a novel putative auxin transport facilitator family, called PIN-LIKES (PILS). Here we illustrate that PILS proteins are required for auxin-dependent regulation of plant growth by determining the cellular sensitivity to auxin. PILS proteins regulate intracellular auxin accumulation at the endoplasmic reticulum and thus auxin availability for nuclear auxin signalling. PILS activity affects the level of endogenous auxin indole-3-acetic acid (IAA), presumably via intracellular accumulation and metabolism. Our findings reveal that the transport machinery to compartmentalize auxin within the cell is of an unexpected molecular complexity and demonstrate this compartmentalization to be functionally important for a number of developmental processes.Prominent auxin carriers with fundamental importance during plant development are PIN-FORMED (PIN) proteins [1][2][3]6,9,15 . PIN1-type auxin carriers regulate the directional intercellular auxin transport at the plasma membrane. In contrast, atypical family member PIN5 regulates intracellular auxin compartmentalization into the lumen of the endoplasmic reticulum and its role in auxin homeostasis was recently identified 15,16 . PIN proteins have a predicted central hydrophilic loop, flanked at each side by five transmembrane domains. We screened in silico for novel PIN-like putative carrier proteins with a predicted topology similar to PIN proteins ( Fig. 1a and Supplementary Fig. 2) and identified a protein family of seven members (Fig. 1b) in Arabidopsis thaliana, which we designated as the PILS proteins. In contrast to the similarities in the predicted protein topology, PIN and PILS proteins do not show pronounced protein sequence identity (10-18%), which limits the identification of PILS proteins by conventional, reciprocal basic local alignment search tool (BLAST) approaches. However, the distinct PIN and PILS protein families contain both the InterPro auxin carrier domain which is an insilico-defined domain, aiming to predict auxin transport function (http://www.ebi.ac.uk/panda/InterPro.html). The PILS putative carrier family is conserved throughout the whole plant lineage, including unicellular algae (such as Ostreococcus tauri and Chlamydomonas reinhardtii) (Supplementary Fig. 3) where PIN proteins are absent 16 , indicating that PILS proteins are evolutionarily older.PILS genes are broadly expressed in various tissues (Fig. 1c) and PILS2-PILS7 were transcriptionally upregulated by auxin application in wild-type seedlings (Fig. 1d-f and Supplementary Fig. 4), indicating a role in auxin-dependent processes. To investigate the potential function of the putative PILS auxi...

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Auxin: Regulation, Action, and Interaction

Abstract: Nearly six decades after the structural elucidation of IAA, many aspects of auxin metabolism, transport and signalling are well established; however, more than a few fundamental questions and innumerable details remain unresolved.

Cited by 1,986 publications

References 344 publications

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

ATAF2, a NAC Transcription Factor, Binds to the Promoter and Regulates NIT2 Gene Expression Involved in Auxin Biosynthesis

A novel putative auxin carrier family regulates intracellular auxin homeostasis in plants

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