A Root Tip-Specific Expressing Anthocyanin Marker for Direct Identification of Transgenic Tissues by the Naked Eye in Symbiotic Studies

The Agrobacterium rhizogenes hairy root transformation system is widely used in symbiotic studies of model legumes. It typically relies on fluorescent reporters, such as DsRed, for identification of transgenic roots. The MtLAP1 transcription factor has been utilized as a reporter system in Medicago truncatula based on production of anthocyanin pigment. Here, we describe a version of this reporter driven by a root-cap specific promoter for direct observation of anthocyanin accumulation in root tips, which allows the identification of transgenic hairy roots by the naked eye. Results from our analysis suggest that the reporter had no significant effects on nodulation of M. truncatula. This approach, by virtue of its strong and specific expression in root cap cells, greatly reduces false positives and false negatives, and its use of an easily scored visible pigment should allow greater versatility and efficiency in root biology studies.

Automated summary

The Agrobacterium rhizogenes hairy root transformation system is commonly used in symbiotic studies of model legumes, utilizing fluorescent reporters for identification of transgenic roots. A MtLAP1 transcription factor reporter system has been developed in Medicago truncatula based on anthocyanin production. This reporter, driven by a root-cap specific promoter, allows direct observation of anthocyanin accumulation in root tips to easily identify transgenic hairy roots. The study showed that this specific expression in root cap cells reduces false positives and negatives while increasing versatility and efficiency in root biology studies.