Highly Efficient Genetic Transformation Methods for the Marine Oleaginous Diatom Fistulifera solaris

Nuclear Transformation of the Marine Pennate Diatom Nitzschia sp. Strain NIES-4635 by Multi-Pulse Electroporation

Nitzschia is one of the largest genera of diatoms found in a range of aquatic environments, from freshwater to seawater. This genus contains evolutionarily and ecologically unique species, such as those that have lost photosynthetic capacity or those that live symbiotically in dinoflagellates. Several Nitzschia species have been used as indicators of water pollution. Recently, Nitzschia species have attracted considerable attention in the field of biotechnology. In this study, a transformation method for the marine pennate diatom Nitzschia sp. strain NIES-4635, isolated from the coastal Seto Inland Sea, was established. Plasmids containing the promoter/terminator of the fucoxanthin chlorophyll a/c binding protein gene (fcp, or Lhcf) derived from Nitzschia palea were constructed and introduced into cells by multi-pulse electroporation, resulting in 500 μg/mL nourseothricin-resistant transformants with transformation frequencies of up to 365 colonies per 108 cells. In addition, when transformation was performed using a new plasmid containing a promoter derived from a diatom-infecting virus upstream of the green fluorescent protein gene (gfp), 44% of the nourseothricin-resistant clones exhibited GFP fluorescence. The integration of the genes introduced into the genomes of the transformants was confirmed by Southern blotting. The Nitzschia transformation method established in this study will enable the transformation this species, thus allowing the functional analysis of genes from the genus Nitzschia, which are important species for environmental and biotechnological development.

Rapid and Efficient Optimization Method for a Genetic Transformation System of Medicinal Plants Erigeron breviscapus

Erigeron breviscapus is an important medicinal plant with high medicinal and economic value. It is currently the best natural biological drug for the treatment of obliterative cerebrovascular disease and the sequela of cerebral hemorrhage. Therefore, to solve the contradiction between supply and demand, the study of genetic transformation of E. breviscapus is essential for targeted breeding. However, establishing an efficient genetic transformation system is a lengthy process. In this study, we established a rapid and efficient optimized protocol for genetic transformation of E. breviscapus using the hybrid orthogonal method. The effect of different concentrations of selection pressure (Hygromycin B) on callus induction and the optimal pre-culture time of 7 days were demonstrated. The optimal transformation conditions were as follows: precipitant agents MgCl2 + PEG, target tissue distance 9 cm, helium pressure 650 psi, bombardment once, plasmid DNA concentration 1.0 μg·μL−1, and chamber vacuum pressure 27 mmHg. Integration of the desired genes was verified by amplifying 1.02 kb of htp gene from the T0 transgenic line. Genetic transformation of E. breviscapus was carried out by particle bombardment under the optimized conditions, and a stable transformation efficiency of 36.7% was achieved. This method will also contribute to improving the genetic transformation rate of other medicinal plants.