Engineering of Chloroplast Genome in Chlamydomonas
Although cases of stable transformation of plastids in higher plants also are now known, initially only Chlamydomonaswas a favourable organism for chloroplast transformation for the following reasons: (i) It has a single large chloroplast. (ii) Photosynthetic mutants are viable, if reduced carbon is provided in the form of acetate.

High efficiency genetic transformation of chloroplasts in Chlamydomonaswas successfully achieved using either of the following two different methods. (i) bombardment cells with DNA-coated tungsten particles; (ii) agitation of cells in the presence of glass beads and DNA that needs to be inserted. Both these methods proved to be very efficient for the transfer of nuclear genes also. Chloroplast trans­formation, like nuclear transformation requires suitable selectable markers. Several such markers that were developed include the following: (i) spectino-mycin resistance (spec^R)and strepto­mycin resistance (str^R), encoded by 16S rDNA; (ii) erythromycin resistance encoded by 23S rDNA; these two markers are separated by 4.2 kb in the chloroplast genome, (iii) atpBgene (coding for a subunit of chloroplast ATPase) essential for photosynthesis. During 1988-1991, atleast four reports of chloroplast transformation in Chlamydomonas were published, three of them utilizing bombardment of cells with DNA-coated tungsten particles, and the fourth utilizing agitation of cell wall deficient cells in the presence of glass beads and DNA.