Nuclear localization signal peptides enhance genetic transformation of Dunaliella salina.

ABSTRACT

BACKGROUND: Dunaliella salina (D. salina) expression system shows a very attractive application prospect, but it currently has a technical bottleneck, namely the low or unstable expression of recombinant proteins. Given the characteristics of cell-penetrating peptides or/and nuclear localization signal (NLS) peptides, this study is the first attempt to improve the transformation rate of foreign gene with trans-activating transcriptional (TAT) protein or/and NLS peptides. METHODS AND RESULTS: Using salt gradient method, exogenous plasmids were transferred into D. salina cells with TAT or TAT/NLS complexes simultaneously. The ß-glucuronidase gene expression was identified by means of histochemical stain and RT-qPCR detection. Through observation with light microscope, TAT-mediating cells exhibit an apparent cytotoxicity even at ratios of 0.5, no significant toxicity was noted in the TAT/plasmid/NLS complex group. It is obvious that with the addition of peptides the toxicity decreases significantly. Histochemical staining showed that the transformants presented blue color under light microscope, but the negative control and blank control are not. Furthermore, based on a TAT/plasmids ratio of 4 with 10 µg NLS peptides mediation, RT-qPCR results demonstrated that the transcripts of target gene were increased by 269 times than that of control group. CONCLUSIONS: This study demonstrated that combination of TAT and NLS peptides can significantly improve the transformation rate and expression level of foreign gene in D. salina system. It offers a promising way for promoting the application and development of D. salina bioreactor.