Nannochloropsis artificial chromosomes (NannoACs) loom on the horizon

Species in genus Nannochloropsis, especially N. oceanica and N. gaditana, have been evolving as the model microalgae for both application and theory studies. The position effect of genome integration, the carrying capability limitation of integrative vectors and the instability of non-integrative vectors have hindered Nannochloropsis genetic modification with concatenate genes and extremely long DNA fragments. The molecular tools including genetic transformation, homologous recombination, gene edition, gene stacking and episome vectors for transient gene expression and diverse reporters and selection markers have been rapidly developing in Nannochloropsis species. The construction of animal and plant artificial chromosomes with "top down" strategy has set fine examples for the construction of Nannochloropsis artificial chromosomes (NannoACs). It seems that the methods and materials to set the foundation for constructing NannoACs are at hands. In this review, we outlined the current status of transgenes in Nannochloropsis species, summarized the limitations of both integrative and non-integrative vectors, and proposed a tentative approach to construct NannoACs by doubling and stabilizing the genome first, and then truncating the natural chromosomes. NannoACs once constructed will facilitate transferring the desired traits and concatenate genes into Nannochloropsis genetic backgrounds, thus contributing towards its genetic improvement and synthetic biological studies.