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)