Groups of Lie type generated by long root elements in F4(K)

Let K be a field and G a quasi-simple subgroup of the Chevalley group F4(K). We assume that G is generated by a class Σ of abstract root subgroups such that there are A,C Σ with [A,C] Σ and any A Σ is contained in a long root subgroup of F4(K). We determine the possibilities for G and describe the embedding of G in F4(K).