Current status and perspectives of genome editing technology for microalgae

Biotechnology for Biofuels, Nov 2017

Genome editing techniques are critical for manipulating genes not only to investigate their functions in biology but also to improve traits for genetic engineering in biotechnology. Genome editing has been greatly facilitated by engineered nucleases, dubbed molecular scissors, including zinc-finger nuclease (ZFN), TAL effector endonuclease (TALEN) and clustered regularly interspaced palindromic sequences (CRISPR)/Cas9. In particular, CRISPR/Cas9 has revolutionized genome editing fields with its simplicity, efficiency and accuracy compared to previous nucleases. CRISPR/Cas9-induced genome editing is being used in numerous organisms including microalgae. Microalgae have been subjected to extensive genetic and biological engineering due to their great potential as sustainable biofuel and chemical feedstocks. However, progress in microalgal engineering is slow mainly due to a lack of a proper transformation toolbox, and the same problem also applies to genome editing techniques. Given these problems, there are a few reports on successful genome editing in microalgae. It is, thus, time to consider the problems and solutions of genome editing in microalgae as well as further applications of this exciting technology for other scientific and engineering purposes.

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Current status and perspectives of genome editing technology for microalgae

Jeon et al. Biotechnol Biofuels Current status and perspectives of genome editing technology for microalgae Seungjib Jeon 0 2 3 Jong‑Min Lim 1 Hyung‑Gwan Lee 6 Sung‑Eun Shin 5 Nam Kyu Kang 0 3 Youn‑Il Park 4 Hee‑Mock Oh 6 WonJ‑oong Jeong 1 Byeong‑ryool Jeong 0 2 3 Yong Keun Chang 0 2 3 0 Advanced Biomass Research and Development Center (ABC) , 291 Daehak‐ro, Yuseong‐gu, Daejeon 34141 , Republic of Korea 1 Plant Systems Engineering Research Center, Korea Research Insti‐ tute of Bioscience and Biotechnology (KRIBB) , 125 Gwahak‐ro, Yuseong‐gu, Daejeon 34141 , Republic of Korea 2 Department of Chemi‐ cal and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak‐ro, Yuseong‐gu, Daejeon 34141 , Republic of Korea 3 Advanced Biomass Research and Development Center (ABC) , 291 Daehak‐ro, Yuseong‐gu, Daejeon 34141 , Republic of Korea 4 Department of Biological Sciences, Chungnam National University , Daejeon 34134 , Republic of Korea 5 LG Chem , 188 Munji‐ro, Yuseong‐gu, Daejeon 34122 , Republic of Korea 6 Cell Factory Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB) , 125 Gwahak‐ro, Yuseong‐gu, Daejeon 34141 , Republic of Korea Genome editing techniques are critical for manipulating genes not only to investigate their functions in biology but also to improve traits for genetic engineering in biotechnology. Genome editing has been greatly facilitated by engineered nucleases, dubbed molecular scissors, including zinc‑ finger nuclease (ZFN), TAL effector endonuclease (TALEN) and clustered regularly interspaced palindromic sequences (CRISPR)/Cas9. In particular, CRISPR/Cas9 has revolutionized genome editing fields with its simplicity, efficiency and accuracy compared to previous nucleases. CRISPR/Cas9‑ induced genome editing is being used in numerous organisms including microalgae. Microalgae have been subjected to extensive genetic and biological engineering due to their great potential as sustainable biofuel and chemical feedstocks. However, progress in microalgal engineering is slow mainly due to a lack of a proper transformation toolbox, and the same problem also applies to genome editing techniques. Given these problems, there are a few reports on successful genome editing in microalgae. It is, thus, time to consider the problems and solutions of genome editing in microalgae as well as further applications of this exciting technology for other scientific and engineering purposes. Genetic engineering; Microalgae; Genome editing; CRISPR/Cas9; Biofuels; GMO conflicts Background Targeted genome modifications are crucial for genetic analyses and genetic engineering in all aspects of biology and related biotechnological fields. Different from random integration of cloned genes for overexpression, specific alterations of the eukaryotic genome have been great challenges for all biologists and biotechnologists. Gene targeting (GT) was initially developed in recombinogenic lower eukaryotes by introducing a homologous transgene into the cell, and by utilizing homologous recombination (HR), scientists were able to knockout or replace genes of interest [ 1 ]. GT has been successfully demonstrated in animals [ 2, 3 ] and plants [4]. However, GT in these higher organisms has been very difficult, in part, because they are not recombinogenic [ 5 ]. Newly developed techniques, including genome editing techniques, have bypassed this hurdle by engineered nucleases, dubbed “molecular scissors,” and the subsequent repair of DNA strand breaks results in mutations or replacements of the genes of interest [ 6 ]. Engineered nucleases include zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced palindromic sequences (CRISPR)/CRISPR-associated protein 9 (Cas9) [ 7 ]. These three, in particular CRISPR/Cas9, will be described for microalgal genome editing in this review even though there have been other nucleases including meganucleases and group II intron-based targetrons adopted for genome editing in other organisms [ 8 ]. These sequence-specific nucleases have enabled researchers to cleave genomic DNA and to obtain mutations of a gene resulting from faulty repair of the cleaved DNA. Microalgae have emerged as important platforms for the production of biofuels and other biomolecules, and genetic engineering of microalgae is, thus, one of the fastest growing biotechnology fields [ 9 ]. In addition to overexpression of genes of interest, genome editing is essential for the suppression of genes interfering with the production of target molecules. However, progress in this field has been hampered by multiple layers of difficulties inherent to microalgae. This review will describe what has been achieved in microalgal genome editing and examine in detail the problems associated with microalgal genome editing and suggest possible solutions. Genome editing has many applications that (...truncated)


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Seungjib Jeon, Jong-Min Lim, Hyung-Gwan Lee, Sung-Eun Shin, Nam Kyu Kang, Youn-Il Park, Hee-Mock Oh, Won-Joong Jeong, Byeong-ryool Jeong, Yong Keun Chang. Current status and perspectives of genome editing technology for microalgae, Biotechnology for Biofuels, 2017, pp. 267,