Identification and molecular characterization of tissue-preferred rice genes and their upstream regularly sequences on a genome-wide level.

BACKGROUND: Gene upstream regularly sequences (URSs) can be used as one of the tools to annotate the biological functions of corresponding genes. In addition, tissue-preferred URSs are frequently used to drive the transgene expression exclusively in targeted tissues during plant transgenesis. Although many rice URSs have been molecularly characterized, it is still necessary and valuable to identify URSs that will benefit plant transformation and aid in analyzing gene function. RESULTS: In this study, we identified and characterized root-, seed-, leaf-, and panicle-preferred genes on a genome-wide level in rice. Subsequently, their expression patterns were confirmed through quantitative real-time RT-PCR (qRT-PCR) by randomly selecting 9candidate tissue-preferred genes. In addition, 5 tissue-preferred URSs were characterized by investigating the URS::GUS transgenic plants. Of these URS::GUS analyses, the transgenic plants harboring LOC_Os03g11350 URS::GUS construct showed the GUS activity only in young pollen. In contrast, when LOC_Os10g22450 URS was used to drive the reporter GUS gene, the GUS activity was detected only in mature pollen. Interestingly, the LOC_Os10g34360 URS was found to be vascular bundle preferred and its activities were restricted only to vascular bundles of leaves, roots and florets. In addition, we have also identified two URSs from genes LOC_Os02G15090 and LOC_Os06g31070 expressed in a seed-preferred manner showing the highest expression levels of GUS activities in mature seeds. CONCLUSION: By genome-wide analysis, we have identified tissue-preferred URSs, five of which were further characterized using transgenic plants harboring URS::GUS constructs. These data might provide some evidence for possible functions of the genes and be a valuable resource for tissue-preferred candidate URSs for plant transgenesis.