7^th Asia-Pacific Biotech Congress

Biography

Biography: Gaston Hui Bon Hoa

Abstract

Viroids are the smallest non encapsidated RNA plant pathogens. They are able to infect dramatically a broad range of plants. The Avsunviroidae such as Avocado sunblotch viroid minus strand (ASBVd(-)) is a compact rod-like circular RNA which possessa catalytic hammerhead ribozyme (HHR) motif responsible for crucial cleavage step during viroid replication. To date little is known regarding the structure and conformation of ASBVd viroids, the catalytic role of Mg2+ and the ways by which such viroids induces diseases. This prompts us to develop a NIR Raman spectroscopy which is a sensitive technique for monitoring RNA’s molecular structure and a Baro-bioreactor designed to allow rapid injections of effectors and sampling out of biomolecular products under pressure for activity studies. ASBVd(-) viroids exhibit a typical A-type RNA conformation with ordered double helical content and a C3’-endo/anti sugar pucker configuration. Deuteration and temperature perturbed differently the RNA’s phosphodiester conformation. Mg2+-activated self-cleavage does not significantly alter the secondary RNA’s structure but noticeable Raman frequency downshifts were observedsuggesting that several phosphodioxy structure, internal loops and hairpins of the cleaved viroids have changed. RNA self-cleavage activity decreased upon deuteration indicating some accessibility of H-bonding network anda rigidity of RNA’s structure. A pressure-induced decrease of the RNA’s self-cleavage pH profile is interpreted as a consequence of some compaction of the structure and a release of catalytic water molecules during catalysis.All these data will constitute the basis for further studies of the interactions of such viroids with therapeutic agents and cell membranes.