| Summary: | <i>Torenia fournieri</i> (<i>T. fournieri</i>) is one of the most widely used horticultural flowers and is considered a potential model plant for the genetic investigation of ornamental traits. In this study, we optimized an efficient protocol for high efficiency preparation and transformation of <i>T. fournieri</i> protoplast. The transformation rate reached ~75% when a <i>35S:GFP</i> construct was used for the transformation. Using this system, we characterized the subcellular localization of several TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) transcription factors (TFs), and found a distinct localization pattern between the CIN and CYC classes of TCP TFs. Furthermore, we also demonstrated the feasibility of the expression of dual luciferase assay system in <i>T. fournieri</i> protoplasts for the measurement of the activity of <i>cis</i>-regulatory elements. Taken together, a well-optimized transient expression system in <i>T. fournieri</i> protoplasts would be crucial for rapid exploration of the gene function or <i>cis</i>-regulatory elements.
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