Transgenic plants chloroplast transformation

Four basic strategies for recombinant protein expression in plants are transient expression, stable nuclear transformed plants, chloroplast transformed plants, and suspension cultures derived from stable transgenic lines. 

Until very recently, high-efficiency chloroplast transformations have been limited to Chlamydomonas and the higher plant Tobaccum. Arabidopsis chloroplasts have been successfully transformed, but none of the regenerated transformed plants were fertile. Chloroplasts from potato leaf cells and rice suspension cells have also been transformed but with poor efficiency as well, and no fertile plants were recovered (Khan et al., 1999 Hibbard et al., 1998). Therefore, a major hurdle is the development of fertile, transgenic, economically important plants. 

Since thousands of copies of the plastid genome can be found per plant cell, extremely high levels of foreign protein are able to accumulate in plants that harbor transgenic chloroplasts. Expression levels greater than 40% of total soluble cellular protein, or 10-100 times higher than protein expression from nuclear transformants, have been detected from plastid transformants. 

Since the first successful transformation of tobacco chloroplasts [83], expression systems based on the transformation of plant plastids has attracted the attention of plant biotechnologists. The features that make this technology so attractive are its potential for high protein yield, along with inherent biosafety features such as limited plastid transfer via pollen (due to maternal inheritance of plastid-encoded genes) [84] and the relatively low probability of transgene movement from the chloroplast to the nucleus [85, 86]. 

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