Production of vaccine
Production of vaccine (expressing foreign proteins) in plants can be achieved through integration of foreign genes into the plant genome and this is a process consist with multiple steps. As the first step, suitable antigen should be identified and isolated (amplified). The gene encoded for the selected antigenic protein should have ability to stimulate production of serum or mucosal antibodies in host body against the pathogen of interested. Next, the gene code of the selected antigenic protein has to be inserted in to a plant expression vector. The vector should contain a strong constitutive promoter which having ability to control expression of antigenic protein within plant as well as selectable marker gene which is important for selection of transgenic plants (Hansen, 1997). Gene transformation can be achieved either through stable transformation or transient transformation. Stable transformation refers to the permanent change in genome of recipient plant cells by permanently integrating target gene in to plant genome. This can be achieved by integrating foreign gene in to the nuclear or plastid genome of the host plant. Biolistic or Agrobacteria mediated transformation techniques are used to achieve the stable transformation. However transient transformation is not involved with chromosomal or permanent gene integration and residing heterologous gene transiently in host cells (Altpeter et al., 2005). However the transient transformation systems produced desired foreign protein or protein expression soon after the gene resides in host plant. As it is not involve with chromosomal integration technology transient gene transformation is simple and rapid but level of foreign protein expression is high (Hansen, 1997). Thus transient protein expression considered as an efficient alternative for the stable protein expression. Two most commonly used techniques to achieve transient transformation is Agrobacteria-mediated transformation and particle bombardment (Altpeter et al., 2005).