Expression of the lacZ reporter gene in sporophytes of the seaweed Laminaria japonica (Phaeophyceae) by gametophyte-targeted transformation.

The seaweed Laminaria japonica (Phaeophyceae) has a two-generation life cycle consisting of haploid gametophytes and diploid sporophytes. Female and/or male gametophytes were transformed using particle bombardment and the histological LacZ assay was performed on sporophytes generated by either parthenogenesis or inbreeding. Female gametophyte-targeted transformation resulted in similar lower efficiencies in both parthenogenetic and zygotic sporophytes, and only a chimeric expression pattern was observed. Male gametophyte-targeted transformation led to a higher efficiency, with 3.5% of the zygotic sporophytes stained completely blue (all-blue), implying the integration of lacZ at the one-cell stage. Polymerase chain reaction analysis using primers specific for a lacZ-vector juncture fragment and subsequent blotting indicated the presence of the introduced gene in the sporophytes. The method reported here has a potential for seaweed transformation using spore-based bombardment followed by the developmental process.