This is based on gene sequence comparisons. The gene in question is closely related to its plant counterpart and phylogenetically distant to any other known ins

This is based on gene sequence comparisons. The gene in question is closely related to its plant counterpart and phylogenetically distant to any other known insect genes. So the most parsimonious explanation is that the gene is horizontally transferred from plants to insects. The chance that it has evolved independently from another insect gene is very, very low.