Toll-like receptors are now counted among the key molecules that alert the immune system to the presence of microbial infections. In 1996, "Toll" was found by Jules A. Hoffmann and his colleagues to have an essential role in the fly's immunity to fungal infection. It worked by activating the synthesis of antimicrobial peptides. Plant homologues were discovered in 1995 (rice XA21), and 2000 ("Arabidopsis" FLS2).