How to Breed Diatoms: Examination of Two Species with Contrasting Reproductive Biology

The diatoms have become a focus of attention as a potential resource for various industrial applications including biofuel production. Initially, progress can be made by screening species held in culture collections or isolated casually from natural samples. To make significant further advances, however, genetic modification (improvement) of promising species will be necessary, by selecting for economically valuable traits. Most diatoms are sexual organisms, and their genetic manipulation via classical plant breeding methods is desirable and possible, alongside modern approaches, for example, transformation. Here we explore the practicalities of diatom breeding by considering experimental control of sex (in the context of the whole life cycle) in two diatom species, Cyclotella meneghiniana and Seminavis robusta. These diatoms exhibit two different kinds of reproductive system, which are largely representative of the groups to which they belong, that is, the centric and pennate diatoms, respectively. We emphasize that efficient exploration of the potential of sexual breeding will also depend largely on progress in understanding many other fundamental aspects of diatom biology, including species-level taxonomy, population studies and biogeography. Unfortunately, the first genomic models, the centric Thalassiosira pseudonana and the pennate Phaeodactylum tricornutum, cannot be involved in investigations of the fundamentals of breeding behaviour in diatoms since, so far at least, there is no indication that these diatoms have a sexual phase in their life cycles.