Transgene Expression in Microalgae-From Tools to Applications.
Transgene Expression in Microalgae-From Tools to Applications.
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DOI：
10.3389/fpls.2016.00505
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发表时间：
2016
影响因子：
5.6
通讯作者：
Shapira M
中科院分区：
文献类型：
--
作者：
Doron L;Segal N;Shapira M
微藻包括存在于水源和沉积物中的一组生物多样性的光合生物。绿色微藻莱茵衣藻（Chlamyeliumreinhardtii）是研究各种生理系统的模式生物。它在光合和异养条件下生长的能力允许非光合突变体的有效生长，使衣原体成为研究光合作用的有用遗传工具。此外，这种绿色酵母可以作为单倍体或二倍体细胞生长，类似于酵母，提供了一个强大的遗传系统。因此，已经开发了针对衣原体的简单有效的转化系统，靶向叶绿体和核基因组。由于微藻包含为生物技术和生物医学工业提供可变优势的丰富物种库，因此进一步开发了用于许多微藻的基因转移技术以允许表达感兴趣的外源蛋白。在叶绿体中表达外源基因使得外源DNA能够通过同源重组靶向特定位点。叶绿体转化还允许从复杂途径引入编码几种酶的基因，可能作为操纵子。在叶绿体中表达外源蛋白质也可以通过将靶基因引入核基因组中来实现，其中蛋白质产物携带靶向信号，所述靶向信号指导转基因产物输入叶绿体，如其它内源性叶绿体蛋白质。外源基因整合到核基因组中大多是随机的，导致不同克隆之间的变异性很大，因此需要进行广泛的筛选。还描述了不同选择方式的使用，特别强调使用除草剂和代谢标记物，其被认为是对环境友好的，与常用的耐药基因相比。最后，尽管开发了广泛的转化工具和方法，但外源基因在微藻中的表达效率低。因此，近年来出现了新的工具来处理这个问题。最后，当C.传统上，reinhardtii被用作开发转化系统及其后续改进的模式生物，类似的技术可以适用于可能具有更高生物技术价值的其他微藻。
Microalgae comprise a biodiverse group of photosynthetic organisms that reside in water sources and sediments. The green microalgae Chlamydomonas reinhardtii was adopted as a useful model organism for studying various physiological systems. Its ability to grow under both photosynthetic and heterotrophic conditions allows efficient growth of non-photosynthetic mutants, making Chlamydomonas a useful genetic tool to study photosynthesis. In addition, this green alga can grow as haploid or diploid cells, similar to yeast, providing a powerful genetic system. As a result, easy and efficient transformation systems have been developed for Chlamydomonas, targeting both the chloroplast and nuclear genomes. Since microalgae comprise a rich repertoire of species that offer variable advantages for biotech and biomed industries, gene transfer technologies were further developed for many microalgae to allow for the expression of foreign proteins of interest. Expressing foreign genes in the chloroplast enables the targeting of foreign DNA to specific sites by homologous recombination. Chloroplast transformation also allows for the introduction of genes encoding several enzymes from a complex pathway, possibly as an operon. Expressing foreign proteins in the chloroplast can also be achieved by introducing the target gene into the nuclear genome, with the protein product bearing a targeting signal that directs import of the transgene-product into the chloroplast, like other endogenous chloroplast proteins. Integration of foreign genes into the nuclear genome is mostly random, resulting in large variability between different clones, such that extensive screening is required. The use of different selection modalities is also described, with special emphasis on the use of herbicides and metabolic markers which are considered to be friendly to the environment, as compared to drug-resistance genes that are commonly used. Finally, despite the development of a wide range of transformation tools and approaches, expression of foreign genes in microalgae suffers from low efficiency. Thus, novel tools have appeared in recent years to deal with this problem. Finally, while C. reinhardtii was traditionally used as a model organism for the development of transformation systems and their subsequent improvement, similar technologies can be adapted for other microalgae that may have higher biotechnological value.