Seminars

Synthesis of novel bio-active metabolites and pharmaceutical proteins in traditional tobacco cultivars may have negative connotations associated with presence of nicotine-alkaloids with additional and possibly cost-prohibitive regulatory hurdles-particularly if extensive purification of proteins is not feasible on a commercial scale. Using Haemagglutinin glycoprotein (HA), an important component of avian influenza (AI) virus infection as a model, we detected significant levels of HA protein in low alkaloid tobacco containing nic1 nic2 mutations (LAFC 53), using constructs employing either plant-optimised HA coding sequence or also native viral HA sequence. Sexual hybridisation of these HA-containing N. tabacum transgenics with a A622-RNAi N. glauca transgenic plant yielded healthy, self-sterile hybrids unable to produce alkaloids, even after wounding. In mice trials, injection of soluble leaf extract from these transgenic hybrids proved to be equally immunogenic as alkaloid-containing HA plant extracts without toxic side effects associated with nicotine-type alkaloids.  We also examined Solanaceous species for potential to produce E. coli B-subunit heat-labile toxin (LTB) in hairy root cultures. Tomato, tobacco and petunia were all were highly receptive to transformation with A. rhizogenes but petunia was the most capable of producing healthy and rapidly growing root cultures with high LTB levels. From safety and bio-containment points of view, use of petunia for production of foreign proteins by hairy roots cultured in vitro has several potential advantages including lack of toxic pyridine alkaloids. These features may be helpful in the context of acquiring regulatory approval for proteins produced using hairy roots of petunia.