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PHABULOSA Mediates an Auxin Signaling Loop to Regulate Vascular Patterning in Arabidopsis
Swedish Univ Agr Sci, Dept Plant Biol, Uppsala BioCtr, Ulls Vag 24E, SE-75651 Uppsala, Sweden.;Swedish Univ Agr Sci, Linnean Ctr Plant Biol Uppsala, Ulls Vag 24E, SE-75651 Uppsala, Sweden..
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Physiological Botany.
Shaanxi Normal Univ, Minist Educ Med Plant Resource & Nat Pharmaceut C, Natl Engn Lab Resource Dev Endangered Chinese Cru, Key Lab,Coll Life Sci, Xian 710062, Peoples R China..
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Physiological Botany.
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2016 (English)In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 170, no 2, 956-970 p.Article in journal (Refereed) PublishedText
Abstract [en]

Plant vascular tissues, xylem and phloem, differentiate in distinct patterns from procambial cells as an integral transport system for water, sugars, and signaling molecules. Procambium formation is promoted by high auxin levels activating class III homeodomain leucine zipper (HD-ZIP III) transcription factors (TFs). In the root of Arabidopsis (Arabidopsis thaliana), HD-ZIP III TFs dose-dependently govern the patterning of the xylem axis, with higher levels promoting metaxylem cell identity in the central axis and lower levels promoting protoxylem at its flanks. It is unclear, however, by what mechanisms the HD-ZIP III TFs control xylem axis patterning. Here, we present data suggesting that an important mechanism is their ability to moderate the auxin response. We found that changes in HD-ZIP III TF levels affect the expression of genes encoding core auxin response molecules. We show that one of the HD-ZIP III TFs, PHABULOSA, directly binds the promoter of both MONOPTEROS (MP)/AUXIN RESPONSE FACTOR5, a key factor in vascular formation, and IAA20, encoding an auxin/indole acetic acid protein that is stable in the presence of auxin and able to interact with and repress MP activity. The double mutant of IAA20 and its closest homolog IAA30 forms ectopic protoxylem, while overexpression of IAA30 causes discontinuous protoxylem and occasional ectopic metaxylem, similar to a weak loss-of-function mp mutant. Our results provide evidence that HD-ZIP III TFs directly affect the auxin response and mediate a feed-forward loop formed by MP and IAA20 that may focus and stabilize the auxin response during vascular patterning and the differentiation of xylem cell types.

Place, publisher, year, edition, pages
2016. Vol. 170, no 2, 956-970 p.
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URN: urn:nbn:se:uu:diva-279586DOI: 10.1104/pp.15.01204ISI: 000369343300028PubMedID: 26637548OAI: oai:DiVA.org:uu-279586DiVA: diva2:908376
Swedish Research Council, 2010-5637Swedish Research Council Formas, 2007:1169Carl Tryggers foundation , CTS 07:64Carl Tryggers foundation , CTS 12:82Magnus Bergvall FoundationHelge Ax:son Johnsons stiftelse
Available from: 2016-03-02 Created: 2016-03-02 Last updated: 2016-03-02Bibliographically approved

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Valdés, Ana ElisaRamachandran, PrashanthUddenberg, DanielCarlsbecker, Annelie
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