Cloning of two splice variants of the rice PTS1 receptor, <i>Os</i>Pex5pL and <i>Os</i>Pex5pS, and their functional characterization using <i>pex5</i>-deficient yeast and Arabidopsis

다국어 초록 (Multilingual Abstract)

<P>Summary</P><P>Using the rice <I>PEX14</I> cDNA as a bait in a yeast two-hybrid assay, two splice variants of the type I peroxisomal targeting signal (PTS1) receptor, <I>Os</I>Pex5pL and <I>Os</I>Pex5pS, were cloned from a pathogen-treated rice leaf cDNA library. The proteins were produced from a single gene by alternative splicing, which generated a full-length variant, <I>OsPEX5L</I>, and a variant that lacked exon 7, <I>OsPEX5S</I>. <I>Os</I>Pex5pL contained 11 copies of the pentapeptide motif WXXXF/Y in its N-terminus, and seven tetratricopeptide repeats in its C-terminus. Expression of <I>OsPEX5L</I> and <I>OsPEX5S</I> predominantly occurred in leaf tissues, and was induced by various stresses, such as exposure to the pathogen <I>Magnaporthe grisea</I>, and treatment with fungal elicitor, methyl viologen, NaCl or hydrogen peroxide. The Arabidopsis T-DNA insertional <I>pex5</I> mutant, <I>Atpex5</I>, which does not germinate in the absence of sucrose and was resistant to indole-3-butyric acid (IBA), was perfectly rescued by over-expression of <I>Os</I>Pex5pL, but not by <I>Os</I>Pex5pS. Using transient expression of <I>Os</I>Pex5pL and <I>Os</I>Pex5pS in the <I>Atpex5</I> mutant, we show that <I>Os</I>Pex5pL translocates both PTS1- and PTS2-containing proteins into the peroxisome by interacting with <I>Os</I>Pex7p, whereas <I>Os</I>Pex5pS is involved only in PTS1-dependent import in Arabidopsis.</P>