Agrobacterium-mediated transformation of the wild orchid Cattleya maxima Lindl

Abstract

Protocorms are unique anatomical structures; they are akin to rhizoids and are formed by young orchid seedlings under physiological conditions. Explanted orchid tissues produce similar structures called protocorm-like bodies (PLBs) when exposed to appropriate <em>in vitro</em> growing conditions. Both the propagative nature of PLBs and the easiness by which they can be generated, make these structures an attractive alternative to seed-mediated production for growing large numbers of plants. To increase somatic embryogenesis and optimize the procedure, PLBs of <em>Cattleya maxima </em>were transformed<em> </em>using the <em>Agrobacterium tumefaciens </em>method. The T-DNA carried a Hygromycin-resistance gene, a visible marker (GFP5-GUSA) and a rice gene encoding the Somatic Embryogenesis Receptor Kinase, deemed to be important for somatic embryogenesis. Treated PLBs generated somatic embryos developing Hygromycin-resistant plantlets. The insertion of T-DNA was confirmed by PCR, and GFP expression was observed using a fluorescent stereomicroscope. Transformed <em>Cattleya maxima</em> PLBs were more efficient in forming somatic embryos (60-80%) than untransformed controls (45-57%), and this contrast was maximized in hormone-free, Murashige and Skoog (MS) medium (80% of the transformed plants compared to 57% of the untransformed ones). This finding supports the notion that SERK<em> </em>plays an important role in Orchid embryogenesis.