Abstract
We succeeded to induce RNAiin Chlamydomonas reinhardtii by introducing inverted repeat DNA construct as a silencer for aadA gene that confers spectinomycin resistance. The highest concentration of spc. was reduced from 3oo micro g/mL to 60 micro g/mL by the induced RNAi. However after 30-50 timed of somatic cell division, cells that survive on the plate containing even 200 micro g/mL of spc reached to about 5 %. Relationship between the threshold and the amount of dsRNA/siRNA was observed apparently, and also extent of cytosine methylation in the inverted repeat construct was clearly affiliated. CG but not CNG methylation was concentrated in the hairpin structure region. Therefore, DNA methylation was probably induced by DNA-DNA interaction and extent of methylation seems change and does not converge through cell divisions.Incomplete RNAi suggests that C. reinhardtii has no RNA dependent RNA polymerase and RNA dependent DNA modification system.
