PT  - JOURNAL ARTICLE
AU  - Casson, Stuart A.
AU  - Chilley, Paul M.
AU  - Topping, Jennifer F.
AU  - Evans, I. Marta
AU  - Souter, Martin A.
AU  - Lindsey, Keith
TI  - The <em>POLARIS</em> Gene of Arabidopsis Encodes a Predicted Peptide Required for Correct Root Growth and Leaf Vascular Patterning
AID  - 10.1105/tpc.002618
DP  - 2002 Aug 01
TA  - The Plant Cell
PG  - 1705--1721
VI  - 14
IP  - 8
4099  - http://www.plantcell.org/content/14/8/1705.short
4100  - http://www.plantcell.org/content/14/8/1705.full
SO  - Plant Cell2002 Aug 01; 14
AB  - The POLARIS (PLS) gene of Arabidopsis was identified as a promoter trap transgenic line, showing β-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 (∼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.