ALGAL TRANSGENICS IN THE GENOMIC ERA¹

Abstract

The last few years have witnessed significant advances in the field of algal genomics. Complete genome sequences from the red alga Cyanidioschyzon merolae and the diatom Thalassiosira pseudonana have been published, the genomes for two more algae (Chlamydomonas reinhardtii and Ostreococcus tauri) are nearing completion, and several others are in progress or at the planning stage. In addition, large-scale cDNA sequencing projects are being carried out for numerous algal species. This wealth of genome data is serving as a powerful catalyst for the development and application of recombinant techniques for these species. The data provide a rich resource of DNA elements such as promoters that can be used for transgene expression as well as an inventory of genes that are possible targets for genetic engineering programs aimed at manipulating algal metabolism. It is not surprising therefore that significant progress in the genetic engineering of eukaryotic algae is being made. Nuclear transformation of various microalgal species is now routine, and progress is being made on the transformation of macroalgae. Chloroplast transformation has been achieved for green, red, and euglenoid algae, and further success in organelle transformation is likely as the number of sequenced plastid, mitochondrial, and nucleomorph genomes continues to grow. Importantly, the commercial application of algal transgenics is beginning to be realized, and algal biotechnology companies are being established. Recent work has shown that recombinant proteins of therapeutic value can be produced in microalgal species, and it is now realistic to envisage the genetic engineering of commercially important species to improve production of valuable algal products. In this article we review the recent progress in algal transgenics and consider possible future developments now that phycology has entered the genomic era.

Comparison of the responses of two Dunaliella strains, Dunaliella salina CCAP 19/18 and Dunaliella bardawil to light intensity with special emphasis on carotenogenesis

“…Efforts for effective production of β-carotene include isolation of carotenogenic strain (Markovits et al 1993), cloning of genes involved in carotenogenesis (Zhu et al 2008), transformation of these genes into microalgae (León-Bañares et al 2004, Walker et al 2005, searching for optimum environmental stimuli that of D. bardawil. Because the actual yield of β-carotene in D. salina CCAP 19/18 was much higher than that of D. bardawil due to much higher growth rate of D. salina CCAP 19/18, the β-carotene yield on the dried mass basis of the cells and the culture volume basis grown under HL was measured (Fig.…”

Transient Transformation of Red Algal Cells: Breakthrough Toward Genetic Transformation of Marine Crop Porphyra Species

“…Eukaryotic algae classified into microalgae and macroalgae (seaweeds) are highly diverse photosynthetic plants that are utilized as human food and animal feed as well as sources of valuable compounds such as fatty acids, pigments, vitamins and polysaccharides (Hallmann, 2007;Sugawara et al, 2011). Because of their importance in ecology and industry, algae are now considered promising organisms for economical and industrial applications and are thus a target of genetic transformation (Walker et al, 2005;Hallmann, 2007;Blouin et al, 2011). To date, genetic transformation has succeeded in microalgae; thus, stably transformed microalgae are now employed to produce recombinant antibodies, vaccines, or bio-hydrogen as well as to analyze the gene functions targeted for engineering (Sun et al, 2003;Zorin et al, 2009;Specht et al, 2010;Wu et al, 2010).…”

Paving the Road to Algal Biofuels with the Development of a Genetic Infrastructure

“…If this biological feat could be achieved in other microalgal species, it would greatly simplify downstream processing by eliminating cell harvesting and lysis; thus, reducing the entire procedure to merely skimming the lipids from the top of the medium. Many accomplishments have already been made in the field of microalgal bioengineering (Leon-Banares et al, 2004;Walker et al, 2005), the most relevant to biofuel production being increased photosynthetic efficiency and light penetration in C. reinhardtii (Mussgnug et al, 2007), but augmented lipid production through genetic alterations has yet to be achieved. Currently, C. reinhardtii remains the workhorse of algal genetic engineering for its history as a model photosynthetic organism (Harris, 2001).…”