 In plants this function was discovered when the "JAW microRNA" of "Arabidopsis" was shown to be involved in the regulation of several genes that control plant shape.In plants, the majority of genes regulated by miRNAs are transcription factors; thus miRNA activity is particularly wide-ranging and regulates entire gene networks during development by modulating the expression of key regulatory genes, including transcription factors as well as F-box proteins.In many organisms, including humans, miRNAs are linked to the formation of tumors and dysregulation of the cell cycle.