Explanatory note on DNA sequence similarity searches in the context of the assessment of horizontal gene transfer from plants to microorganisms

Guidance of the EFSA Panel on Genetically Modified Organisms assists applicants in the preparation and presentation of their applications by describing elements and data requirements for the risk assessment and monitoring of genetically modified (GM) plants. This note to the guidance provides a scientific rationale and further instructions for the use of bioinformatic analyses to identify GM plant sequences with sufficient identity to promote homologous recombination and impact on horizontal gene transfer from plants to microorganisms. The evaluation of the extent of identity between GM event DNA sequences and the DNA present in microbial genomes, with bioinformatic analyses, is considered necessary to perform a proper problem formulation to define the probability for horizontal gene transfer in the environmental risk assessment of GM plants. Further details on how to perform such analyses are outlined and include a complete description of all sequences present in the insert, and recommendations on the algorithms, parameters and databases to be used as well as on a relevant length of sequence identity between the GM plant sequences and those present in microbial genomes.