LATERAL ROOT PRIMORDIA 1 of maize acts as a transcriptional activator in auxin signalling downstream of the Aux/IAA gene rootless with undetectable meristem 1.
Only little is known about target genes of auxin signalling downstream of the Aux/IAA-ARF module. In the present study, it has been demonstrated that maize lateral root primordia 1 (lrp1) encodes a transcriptional activator that is directly regulated by the Aux/IAA protein ROOTLESS WITH UNDETECTABLE MERISTEM 1 (RUM1). Expression of lrp1 is confined to early root primordia and meristems and is auxin-inducible. Based on its primary protein structure, LRP1 is predicted to be a transcription factor. This notion is supported by exclusive LRP1 localization in the nucleus and its ability to activate downstream gene activity. Based on the observation that lrp1 transcription is completely repressed in the semi-dominant gain of function mutant rum1, it was demonstrated that the lrp1 promoter is a direct target of RUM1 proteins. Subsequently, promoter activation assays indicated that RUM1 represses the expression of a GFP reporter fused to the native promoter of lrp1. Constitutive repression of lrp1 in rum1 mutants is a consequence of the stability of mutated rum1 proteins which cannot be degraded by the proteasome and thus constitutively bind to the lrp1 promoter and repress transcription. Taken together, the repression of the transcriptional activator lrp1 by direct binding of RUM1 to its promoter, together with specific expression of lrp1 in root meristems, suggests a function in maize root development via the RUM1-dependent auxin signalling pathway.
INRES, Institute of Crop Science and Resource Conservation, Crop Functional Genomics, Friedrich-Ebert-Allee 144, University of Bonn, D-53113 Bonn, Germany Center for Molecular Cell and Systems Biology, College of Life Science, Fujian Agriculture & Forestry University, 350002 Fuzhou, China.
Yanxiang
Y
Zhang
ZMBP, Center for Plant Molecular Biology, Department of General Genetics, University of Tuebingen, D-72076 Tuebingen, Germany.
Inga
I
von Behrens
ZMBP, Center for Plant Molecular Biology, Department of General Genetics, University of Tuebingen, D-72076 Tuebingen, Germany.
Roman
R
Zimmermann
INRES, Institute of Crop Science and Resource Conservation, Crop Functional Genomics, Friedrich-Ebert-Allee 144, University of Bonn, D-53113 Bonn, Germany.
Yvonne
Y
Ludwig
INRES, Institute of Crop Science and Resource Conservation, Crop Functional Genomics, Friedrich-Ebert-Allee 144, University of Bonn, D-53113 Bonn, Germany.
Stefan
S
Hey
INRES, Institute of Crop Science and Resource Conservation, Crop Functional Genomics, Friedrich-Ebert-Allee 144, University of Bonn, D-53113 Bonn, Germany hochholdinger@uni-bonn.de.
Frank
http://orcid.org/0000-0002-5155-0884
F
Hochholdinger
D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D018519:Meristem / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D026801:Synteny; D015534:Trans-Activators / Q000378:metabolism*; D003313:Zea mays / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D007210:Indoleacetic Acids; D010940:Plant Proteins; D015534:Trans-Activators
Aux/IAA; LATERAL ROOT PRIMORDIA 1 (LRP1); RUM1; crown root; differentiation zone; maize; transcriptional activator.