Plant Plastid Engineering

Wani, Shabir H.; Haider, Nadia; Kumar, Hitesh; Singh, N.B.

Ruf et al. [60] believe that plastid transformation is considered as a superb tool for ensuring transgene containment and improving the biosafety of transgenic plants. However, they pointed out that plastid transformation would only be effective as a biocontainment measure when applied on a landscape scale if it were combined additional mechanisms such as mitigating genes genetic use restriction technology, and/or male sterility [63] . In a recent study, it has been demonstrated that the use of plastid transformation would provide an imperfect biocontainment for GM oilseed rape (Brassica napus L.) in the United Kingdom [64] . In another study, Allainguillaume et al. [65] revealed that chloroplast transformation may slow transgene recruitment in two settings, but actually accelerate transgene spread in a third. Plastid transformation has become an attractive alternative to nuclear gene transformation due to several other advantages [3] . The high ploidy number of the plastid genome allows high levels (up to 1-40% of total protein) of protein expression or expression of the transgene [28] . Daniell et al. [66] and Hou et al. [44] reported that while nuclear transgenes typically result in 0.5 -3% of total proteins, concentration of proteins expressed by plastid transgenes is much higher; up to 18%. The greater production of the expressed protein is possible because plastid transgenes are present as multiple copies per plant cell, and they are little affected by phenomena like pre-or post-transcriptional silencing. Other advantages of plastid engineering are the capacity to express multiple genes from polycistronic messenger RNA (mRNA) [31] , and the absence of epigenetic effects and gene silencing [40] .