Expression and Regulation of the RSI-1 Gene during Lateral Root Initiation

다국어 초록 (Multilingual Abstract)

The tomato gene RSI-1 was previously identified as a molecular marker for auxin-induced lateral root initiation. We have further characterized the expression mode of the RSI-1 gene in tomato and Arabidopsis thaliana. Northern blot analyses revealed that the gene was induced specifically by auxin in tomato roots and hypocotyls. For experiments with transgenic plants, the 5' flanking region of the RSI-1 gene was linked to a GUS reporter gene, then transformed into tomato and Arabidopsis. In these transgenic tomato plants, GUS activity was detected at the sites of initiation for lateral and adventitious roots. Expression of the fusion gene was auxin-dependent and tissue-specific. This was consistent with results from the northern blot analyses. In transgenic Arabidopsis, the overall expression pattern of the RSI-GUS gene, including tissue specificity and auxin inducibility, was comparable to that in transgenic tomato seedlings. These results indicate that an identical regulatory mechanism for lateral root initiation might be conserved in both plants. Thus, the expression mode of the RSI-GUS gene in Arabidopsis mutants defective in lateral root development should be investigated to provide details of this process.