In vitro plant regeneration and de novo differentiation of secretory trichomes in Passiflora foetida L. (Passifloraceae)

The only species in the genus Passiflora (Passifloraceae) known to produce resin glands is P. foetida. These glands are secretory trichomes mainly present on the floral bracts and leaf stipules. The secretion produced by these glands has received attention recently due to the presence of substances with pharmacological properties. Attempts to apply in vitro cell culture methods for the large scale production of highly valuable metabolites has been rather limited due to the fact that these compounds are produced by highly differentiated secretory cells in trichomes which are seldom obtained or because differentiation is inhibited by in vitro conditions. Here we describe the in vitro plant regeneration of P. foetida obtained via organogenesis, using mature zygotic embryos as explants. Differentiated plantlets and, more important, the de novo differentiation of secretory trichomes in vitro could be observed in less than 30 days. There was a clear effect of the concentration of 2,4-dichlorophenoxyacetic acid in the culture media on the regeneration of plants and on the differentiation of glandular trichomes. Our results should be useful for the micropropagation of P. foetida, as well as for studies of the process of secretory trichome differentiation and the implemention of biotechnological methodologies for in vitro mass production of passifloricin and/or other substances present in the P. foetida resin.