| Summary: | Selecting transformed plants is generally time consuming and laborious. To develop a method for transgenic plant selection without the need for antibiotics or herbicides, we evaluated the suitability of the R2R3 MYB transcription factor gene <i>CaAN2</i> from purple chili pepper (<i>Capsicum annuum</i>) for use as a visible selection marker. <i>CaAN2</i> positively regulates anthocyanin biosynthesis. Transient expression assays in tobacco (<i>Nicotiana tabacum</i>) leaves revealed that <i>CaAN2</i> actively induced sufficient pigment accumulation for easy detection without the need for a basic helix-loop-helix (bHLH) protein as a cofactor; similar results were obtained for tobacco leaves transiently co-expressing the anthocyanin biosynthesis regulators bHLH B-Peru from maize and R2R3 MYB mPAP1D from Arabidopsis. Tobacco plants harboring <i>CaAN2</i> were readily selected based on their red color at the shoot regeneration stage due to anthocyanin accumulation without the need to impose selective pressure from herbicides. Transgenic tobacco plants harboring <i>CaAN2</i> showed strong pigment accumulation throughout the plant body. The ectopic expression of <i>CaAN2</i> dramatically promoted the transcription of anthocyanin biosynthetic genes as well as regulators of this process. The red coloration of tobacco plants harboring <i>CaAN2</i> was stably transferred to the next generation. Therefore, anthocyanin accumulation due to <i>CaAN2</i> expression is a useful visible trait for stable transformation, representing an excellent alternative selection system for transgenic plants.
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