| Summary: | <p>Abstract</p> <p>Background</p> <p>Plants living at high altitudes are typically exposed to elevated UV-B radiation, and harbor mechanisms to prevent the induced damage, such as the accumulation of UV-absorbing compounds. The maize R2R3-MYB transcription factor P1 controls the accumulation of several UV-B absorbing phenolics by activating a subset of flavonoid biosynthetic genes in leaves of maize landraces adapted to high altitudes.</p> <p>Results</p> <p>Here, we studied the UV-B regulation of <it>P1</it> in maize leaves of high altitude landraces, and we investigated how UV-B regulates P1binding to the <it>CHS</it> promoter in both low and high altitude lines. In addition, we analyzed whether the expansion in the <it>P1</it> expression domain between these maize landraces and inbred lines is associated to changes in the molecular structure of the proximal promoter, distal enhancer and first intron of <it>P1</it>. Finally, using transient expression experiments in protoplasts from various maize genotypes, we investigated whether the different expression patterns of <it>P1</it> in the high altitude landraces could be attributed to <it>trans</it>- or <it>cis</it>-acting elements.</p> <p>Conclusions</p> <p>Together, our results demonstrate that, although differences in <it>cis</it>-acting elements exist between the different lines under study, the different patterns of P1 expression are largely a consequence of effects in <it>trans.</it></p>
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