Casson Stuart A, Chilley Paul M, Topping Jennifer F, Evans I Marta, Souter Martin A, Lindsey Keith
Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, United Kingdom.
Plant Cell. 2002 Aug;14(8):1705-21. doi: 10.1105/tpc.002618.
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.
拟南芥的POLARIS（PLS）基因被鉴定为一个启动子捕获转基因系，其β-葡萄糖醛酸酶融合基因主要在胚胎和幼苗根中表达，地上部分表达较低。PLS基因座的克隆显示，启动子捕获T-DNA已插入一个短开放阅读框（ORF）。通过cDNA末端快速扩增PCR、RNA凝胶印迹分析和核糖核酸酶保护试验表明，PLS ORF位于一个短的（约500个核苷酸）生长素诱导转录本内，编码一个预测的36个氨基酸残基的多肽。pls突变体表现出短根表型和叶片维管束化减少。与野生型相比，pls根对外源细胞分裂素反应过度，细胞分裂素诱导基因ARR5/IBC6的表达增加。与野生型相比，pls幼苗对外源生长素的生长抑制作用反应也较弱，生长素诱导基因IAA1的表达降低。cDNA的PLS肽编码区部分互补pls突变，且活性需要PLS ORF的ATG，证明了肽编码ORF的功能。PLS ORF的异位表达减少了外源细胞分裂素对根生长的抑制，并增加了叶片维管束化。我们提出，PLS是正确的生长素-细胞分裂素稳态调节根生长和叶片维管束模式所必需的。
