Enhanced anthocyanin synthesis in foliage plant Caladium bicolor

Abstract

A protocol was developed for Agrobacterium-mediated genetic transformation of monocotyledon foliage plant Caladium bicolor cv. Jackie Suthers using leaf disc and petiole as the explants. The explants were inoculated with Agrobacterium strain LBA4404 harboring a binary vector with the maize anthocyanin regulatory gene Lc under the control of the cauliflower mosaic virus promoter. Callus formation was induced in MS medium supplemented with 0.5 mg/l 6-benzylaminopurine (6-BA), 0.1 mg/1 2,4-dichlorophenoxyacetic acid (2,4-D), 30 g/l sucrose and kanamycin 50 mg/l for selection. Resistant calli were induced for shoot generation in MS medium with 2 mg/l 6-BA and 0.2 mg/l alpha-naphthaleneacetic acid. As much as 10% of the explants gave rise to kanamycin-resistant shoots with our procedure. Transformed plants had enhanced anthocyanin accumulation in the roots, leaves and stems (epidermis and vascular bundles). Integration of the transgene into the host genome was confirmed by genomic Southern blot hybridization, and RNA blot hybridization analysis indicated that the expression of the transgene correlated with anthocyanin accumulation. This investigation illustrates the utility of anthocyanin regulatory genes in the genetic manipulation of the color of foliage plants. It also supports the premise that the Lc gene can be used as a powerful non-destructive cell autonomous visual marker in a wide variety of plants, as exemplified by the perfect symmetrical half-green/half-red plant presumably derived from the symmetrical division of one transgenic and one non-transgenic precursor meristematic cell.