Transformation of nonselectable reporter genes in marine diatoms

We report the genetic transformation of two marine diatoms by microparticle bombardment. The pennate diatom Phaeodactylum tricornutum was transformed with the bacterial gene Sh ble from Streptoalloteichus hindustanus, which c onfers resistance to the antibiotics phleomycin and zeocin. Transformants c ontained between 1 and 10 copies of the exogenous DNA integrated into the g enome by illegitimate recombination at apparently random locations. Transfo rmation efficiencies were around 10(-6), and individual cell lines could be maintained at -80 degrees C following cryopreservation. Also, P. tricornut um could be transformed simultaneously with two different plasmids, one con taining the Sh ble gene and another containing the firefly luciferase gene (LUC) under control of a promoter derived from a fucoxanthin, chlorophyll a /c-binding protein gene (FCP). In these cotransformants, LUC activity was l ight inducible. The transient transformation of the centric diatom Thalassi osira weissflogii with the bacterial beta-glucuronidase (GUS) gene has also been achieved using similar transformation technology. The availability of gene transfer protocols for marine diatoms, together with a range of funct ional reporter genes and regulated expression systems, will permit molecula r dissection of their biology and allow an assessment of the biotechnologic al potential of these organisms.