Analysis of the P1promoter in response to UV-B radiation in allelic variants of high-altitude maize

Abstract

BackgroundPlants 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.ResultsHere, we studied the UV-B regulation of P1 in maize leaves of high altitude landraces, and we investigated how UV-B regulates P1binding to the CHS promoter in both low and high altitude lines. In addition, we analyzed whether the expansion in the P1 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 P1. Finally, using transient expression experiments in protoplasts from various maize genotypes, we investigated whether the different expression patterns of P1 in the high altitude landraces could be attributed to trans- or cis-acting elements.ConclusionsTogether, our results demonstrate that, although differences in cis-acting elements exist between the different lines under study, the different patterns of P1 expression are largely a consequence of effects in trans.

Integrated genomics-based mapping reveals the genetics underlying maize flavonoid biosynthesis

“…Moreover, the different colors exhibited by flavonoids can attract pollinators and thus are highly important in plant reproduction [8, 9]. They can additionally function as an UV absorbing compounds protecting plants from the UV-B radiation [10, 11], and can also serve as anti-pathogen such as maysin and GCA (chlorogenic acid) in maize [12, 13]. Flavonoids are necessary for conditional male fertility in maize [14] and are also involved in seed coat development [15], regulating the transport of phytohormones [16, 17], and providing signals to symbionts in plants [18].…”

P1 Epigenetic Regulation in Leaves of High Altitude Maize Landraces: Effect of UV-B Radiation

“…High-altitude maize landraces grown from 2000 to 3400 m naturally receive higher UV-B than plants at lower altitudes and similar latitudes (McKenzie et al, 2007 ). Previously, we demonstrated that some maize landraces adapted to high altitudes accumulate flavones and express P1 in leaves and other green tissues in the presence of UV-B, in sharp departure to the floral-organ specific expression domain of P1 found in most other maize inbred lines (Casati and Walbot, 2005 ; Rius et al, 2012 ). These results suggest that a large P1 allelic diversity may exist as a consequence of plants growing in diverse environments.…”

“…For example, the P1-wr (white pericarp and red cob) allele is composed of eleven gene copies arranged in a tandem head-to-tail array, and the B73 inbred line present a multiple copy P1 cluster (Goettel and Messing, 2009 ). Also, landraces adapted to different altitudes have different P1 copies (Rius et al, 2012 ). Comparison of the expression properties of the P1- wr and the P1- rr alleles has suggested that P1- wr is regulated both transcriptionally and post-transcriptionally in floral tissues (Chopra et al, 1996 ).…”

The Dominant and Poorly Penetrant Phenotypes of Maize Unstable factor for orange1 Are Caused by DNA Methylation Changes at a Linked Transposon

“…There also is evidence that sucrose can activate anthocyanin production in maize (Kim et al, 2006;Ma et al, 2009). Unlike anthocyanin production, the expression of p1 has not been shown to be responsive to sugar in maize, although it has been shown to be induced by UV-B treatment in high-altitude landraces (Falcone Ferreyra et al, 2010;Rius et al, 2012). It will be interesting to find out if UV-B treatment or other stresses involve sugar accumulation and how they relate to the expression of p1.…”