title: Diversity of stability, localization, interaction and control of downstream gene activity in the Maize Aux/IAA protein family.
abstract: AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) proteins are central regulators of auxin signal transduction. They control many aspects of plant development, share a conserved domain structure and are localized in the nucleus. In the present study, five maize Aux/IAA proteins (ZmIAA2, ZmIAA11, ZmIAA15, ZmIAA20 and ZmIAA33) representing the evolutionary, phylogenetic and expression diversity of this gene family were characterized. Subcellular localization studies revealed that ZmIAA2, ZmIAA11 and ZmIAA15 are confined to the nucleus while ZmIAA20 and ZmIAA33 are localized in both the nucleus and the cytoplasm. Introduction of specific point mutations in the degron sequence (VGWPPV) of domain II by substituting the first proline by serine or the second proline by leucine stabilized the Aux/IAA proteins. While protein half-life times between ∼11 min (ZmIAA2) to ∼120 min (ZmIAA15) were observed in wild-type proteins, the mutated forms of all five proteins were almost as stable as GFP control proteins. Moreover, all five maize Aux/IAA proteins repressed downstream gene expression in luciferase assays to different degrees. In addition, bimolecular fluorescence complementation (BiFC) analyses demonstrated interaction of all five Aux/IAA proteins with RUM1 (ROOTLESS WITH UNDETECTABLE MERISTEM 1, ZmIAA10) while only ZmIAA15 and ZmIAA33 interacted with the RUM1 paralog RUL1 (RUM-LIKE 1, ZmIAA29). Moreover, ZmIAA11, ZmIAA15 ZmIAA33 displayed homotypic interaction. Hence, despite their conserved domain structure, maize Aux/IAA proteins display a significant variability in their molecular characteristics which is likely associated with the wide spectrum of their developmental functions.
authors.affiliation: Institute of Crop Science and Resource Conservation (INRES), Crop Functional Genomics, University of Bonn, Bonn, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Ludwig
authors.affiliation: Center for Plant Molecular Biology (ZMBP), Central Facilities, University of Tübingen, Tübingen, Germany.
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Berendzen
authors.affiliation: Institute of Crop Science and Resource Conservation (INRES), Crop Functional Genomics, University of Bonn, Bonn, Germany; College of Resources and Environment (RCBB), Southwest University, Chongqing, China.
authors.forename: Changzheng
authors.initials: C
authors.lastname: Xu
authors.affiliation: Institute for Crop Science, Bioinformatics Unit, University of Hohenheim, Stuttgart, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Piepho
authors.affiliation: Institute of Crop Science and Resource Conservation (INRES), Crop Functional Genomics, University of Bonn, Bonn, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Hochholdinger
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D006207:Half-Life; D007210:Indoleacetic Acids / Q000378:metabolism*; D010802:Phylogeny; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; C030737:indoleacetic acid