Comparative Expression Analysis of Rice and <i>Arabidopsis</i> Peroxiredoxin Genes Suggests Conserved or Diversified Roles Between the Two Species and Leads to the Identification of Tandemly Duplicated Rice Peroxiredoxin Genes Differentially Expressed in

다국어 초록 (Multilingual Abstract)

<P><B>Background</B></P><P>Peroxiredoxins (PRXs) have recently been identified as plant antioxidants. Completion of various genome sequencing projects has provided genome-wide information about PRX genes in major plant species. Two of these -- <I>Oryza sativa</I> (rice) and <I>Arabidopsis</I> -- each have 10 PRX members. Although significant progress has been made in understanding their biological roles in <I>Arabidopsis</I>, those functions in rice, a model crop plant, have not been well studied.</P><P><B>Results</B></P><P>We performed a comparative expression analysis of rice and <I>Arabidopsis</I> PRXs. Our phylogenetic analysis revealed that one subgroup contains three rice and three <I>Arabidopsis</I> Type-II PRXs that are expressed ubiquitously. This suggests that they are involved in housekeeping functions to process reactive oxygen species (ROS). Within the second subgroup, expression of <I>Os1-CysPrxA (LOC_Os7g44430)</I> and <I>AtOs1-CysPrx</I> is conserved in seeds while <I>Os1-CysPrxB (LOC_Os7g44440)</I> shows a root-preferential pattern of expression. We used transgenic plants expressing the GUS reporter gene under the control of the promoters of these two tandem duplicates to confirm their meta-expression patterns. Our GUS expression data from developing seeds and those that were germinating indicated that <I>Os1-CysPrxB</I> is involved in root development, as initiated from the embryo, while <I>Os1-CysPrxA</I> has roles in regulating endosperm development near the aleurone layer. For the third and fourth subgroups, the rice PRXs are more likely to show leaf/shoot-preferential expression, while those from <I>Arabidopsis</I> are significantly expressed in the flowers and seeds in addition to the leaf/shoot. To determine the biological meaning of those expression patterns that were dominantly identified in rice PRXs, we analyzed three rice genes showing leaf/shoot-preferential expression in a mutant of the light-responsive <I>1-deoxy-D-xylulose 5-phosphate reductoisomerase</I> (<I>dxr</I>) gene and found that two of them were significantly down-regulated in the mutant.</P><P><B>Conclusion</B></P><P>A global expression analysis of the PRX family in rice identified tandem duplicates, <I>Os1-CysPrxA</I> and <I>Os1-CysPrxB,</I> in the 1-CysPrx subgroup that are differentially expressed in developing seeds and germinating seeds. Analysis of the <I>cis</I>-acting regulatory elements (CREs) revealed unique CREs responsible for embryo and root or endosperm-preferential expression. In addition, the presence of leaf/shoot-preferential PRXs in rice suggests that they are required in that crop because those plants must tolerate a higher light intensity in their normal growth environment when compared with that of <I>Arabidopsis</I>. Downregulation of two <I>PRX</I>s in the <I>dxr</I> mutant causing an albino phenotype, implying that those genes have roles in processing ROS produced during photosynthesis. Network analysis of four PRXs allowed us to model regulatory pathways that explain the underlying protein interaction network. This will be a useful hypothetical model for further study.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12284-017-0170-5) contains supplementary material, which is available to authorized users.</P>