The POLARIS gene of Arabidopsis encodes a predicted peptide required for correct root growth and leaf vascular patterning.
The POLARIS (PLS) gene of Arabidopsis was identified as a promoter trap transgenic line, showing beta-glucuronidase fusion gene expression predominantly in the embryonic and seedling root, with low expression in aerial parts. Cloning of the PLS locus revealed that the promoter trap T-DNA had inserted into a short open reading frame (ORF). Rapid amplification of cDNA ends PCR, RNA gel blot analysis, and RNase protection assays showed that the PLS ORF is located within a short ( approximately 500 nucleotides) auxin-inducible transcript and encodes a predicted polypeptide of 36 amino acid residues. pls mutants exhibit a short-root phenotype and reduced vascularization of leaves. pls roots are hyperresponsive to exogenous cytokinins and show increased expression of the cytokinin-inducible gene ARR5/IBC6 compared with the wild type. pls seedlings also are less responsive to the growth-inhibitory effects of exogenous auxin and show reduced expression of the auxin-inducible gene IAA1 compared with the wild type. The PLS peptide-encoding region of the cDNA partially complements the pls mutation and requires the PLS ORF ATG for activity, demonstrating the functionality of the peptide-encoding ORF. Ectopic expression of the PLS ORF reduces root growth inhibition by exogenous cytokinins and increases leaf vascularization. We propose that PLS is required for correct auxin-cytokinin homeostasis to modulate root growth and leaf vascular patterning.
Casson
Stuart A
SA
Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, United Kingdom.
Chilley
Paul M
PM
Topping
Jennifer F
JF
Evans
I Marta
IM
Souter
Martin A
MA
Lindsey
Keith
K
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003583:Cytokinins / Q000494:pharmacology; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007210:Indoleacetic Acids / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D018515:Plant Leaves / Q000166:cytology / Q000254:growth & development*; D018517:Plant Roots / Q000254:growth & development*; D030821:Plants, Genetically Modified; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; D003583:Cytokinins; D018076:DNA, Complementary; D007210:Indoleacetic Acids; C469251:polaris protein, Arabidopsis