Plastome Engineering in Microalgae: The Future of the Green Biotechnology

The chloroplast is a green sophisticated organelle that is often considered as the biosynthetic center of the plant cell. The first successful chloroplast transformation was performed in the microalgae Chlamydomonas, and since then the algae chloroplast appears very attractive for modifying biochemical pathways, either by changing expression of existing genes or by adding genes designed to produce new valuable products with medical and industrial applications. We discuss a series of technical achievements developed for the success of algal chloroplast transformation. However, there are limitations of the existing methodology which leads to relatively low expression yields for the desired products in microalgae. Therefore, it is really necessary to increase the knowledge of transcriptional and posttranscriptional control of gene expression in the chloroplast and the role of the algae plastid RNases. Chlamydomonas to this day constitutes the only algae routinely used in transplastomic technology for engineering metabolic pathways and molecular farming. We also review recent products such as enzymes and pharmaceutical proteins which have been successfully produced with plastome engineering.