Transposition Of PiggyBac Element Is Attributed To Transient Expression Of PB Transposase In Chlamydomonas Reinhardtii

The cut-and-paste piggyBac (PB) transposon system has been shown to be a useful tool for genetic modification in a number of organisms including mammals, insects, and yeast. However, little is known whether it is active in the green microalga Chlamydomonas reinhardtii. To address this issue, we first constructed stable PB element-containing C. reinhardtii strains bearing either a single copy or multiple copies of PB element. Subsequently, we transiently expressed TPase or codon-optimized crTPase in the PB element-containing strains to assay for transposition of PB element using RFLP methodology. Through observing the disappearance and occurance of the fragments in different size on the RFLP pattern map, it can be shown that the PB transposition incident whether occur or not.Our analyses show that initial RFLP patterns of PB element are altered in cells one week and two weeks after plasimds containing TPase or crTPase expression cassette. Furthermore, we find that illegitimate excision of PB element occasionally occurs at the short repeat sequences 5’_TTT-3’and 5’-ACGCAG-3’, but the standard excision site 5’-TTAA-3’.Most of the cells will be dead when the PB TPase excise in the legitimate site,while several strains can surive the toxic of TPase after illegitimate excision of PB element. Taken together, our results show that the TPase and crTPase are active in transposition of PB element in C. reinhardtii. Hence, we propose that PB transposon systems can be adopted for genome modification in C. reinhardtii.