A Biolistic-Mediated Virus-Induced Gene Silencing in Apocynaceae to Map Biosynthetic Pathways of Alkaloids.

Monoterpene indole alkaloids (MIAs) are specialized metabolites synthesized in many plants of the Apocynaceae family including Catharanthus roseus and Rauvolfia sp. MIAs are part of the chemical arsenal that plants evolved to face pet and herbivore attacks, and their high biological activities also confer pharmaceutical properties exploited in human pharmacopeia. Developing robust and straightforward tools to elucidate each step of MIA biosynthetic pathways thus constitutes a prerequisite to the understanding of Apocynaceae defense mechanisms and to the exploitation of MIA cytotoxicity through their production by metabolic engineering. While protocols of virus-induced gene silencing (VIGS) based on Agrobacterium-based transformation have emerged, the recalcitrance of Apocynaceae to this type of transformation prompted us to develop an universal procedure of VIGS vector inoculation. Such procedure relies on the delivery of the transforming plasmids through a particle bombardment performed using a biolistic device and offers the possibility to overcome host specificity to silence genes in any plant species. Using silencing of geissoschizine oxidase as an example, we described the main steps of this biolistic mediated VIGS in C. roseus and R. tetraphylla.