Title: PLANT PIGMENT PRODUCTION AS AN INDICATOR OF PTGS Authors
Submitted to: International Congress of Plant Molecular Biology
Publication Type: Proceedings
Publication Acceptance Date: April 12, 2006
Publication Date: August 25, 2006
Citation: Velten, J.P., Cazzonelli, C.I. 2007. Plant pigment production as an indicator of PTGS [abstract]. International Congress of Plant Molecular Biology, August 20-25, 2006, Adelaide, Australia. August 20-25, 2006. CD-ROM. Technical Abstract: “Co-suppression” associated loss of flower pigmentation in petuna plants engineered to over-express chalcone synthase was one of the first clear indicators of the natural process of RNA-associated gene silencing in plants. We have been exploring the possible use of engineered anthocyanin over-production in vegetative tissues as a visual indicator of gene activation and silencing. Constitutive over-expression of the Arabidopsis PAP1 or PAP2 genes, encoding transcription factors from the myb family (AtMYB75 and AtMYB 90, respectively), can result in ectopic over-production of anthocyanin pigments in both Arabidopsis and other plant species. The resulting pigment accumulation leads to a clearly visible red-to-purple color in the leaves, stems and flower of select transgenic lines. In order to examine the utility of MYB-induced pigmentation as a visible reporter we have generated transgenic N. tabacum and N. Benthamiana lines that over-express the Arabidopsis PAP2 gene. Agro-infiltration of leaves on purple tobacco plants, using a T-DNA construct that produces dsRNA against PAP2, generates a loss of anthocyanin pigmentation, both at the site of infusion, and in leaves distal to the treated leaf. The signal for distal silencing moves upward in the plant and is transient, affecting only 2-4 leaves at an early stage of emergence. Although subsequently emergent leaves return to the purple phenotype, the distally silenced leaves remain green until senescence. We are exploring the nature of the silencing signal and the molecular status of the PAP2 transgene within silenced and active leaf tissues.