Associated component of the WMM complex, a complex that mediates N6-methyladenosine (m6A) methylation of mRNAs, a modification that plays a role in the efficiency of mRNA splicing and is required for sex determination (PubMed:29535189, PubMed:29555755). In the WMM complex, acts as a key regulator of m6A methylation by bridging fl(2)d to the RNA-binding component nito (PubMed:29535189). Required for sex determination and dosage compensation via Sxl alternative splicing: m6A methylation acts as a key regulator of Sxl pre-mRNA and promotes female-specific alternative splicing of Sxl, which determines female physiognomy (PubMed:29535189, PubMed:29555755). Component of the WMM complex, a N6-methyltransferase complex composed of a catalytic subcomplex, named MAC, and of an associated subcomplex, named MACOM (PubMed:29535189, PubMed:29555755). The MAC subcomplex is composed of Ime4/Mettl3 and Mettl14 (PubMed:29535189, PubMed:29555755). The MACOM subcomplex is composed of fl(2)d, Flacc/Xio, Hakai, vir, and, in some cases of nito (PubMed:29535189, PubMed:29555755). Widely expressed during embryogenesis but shows enrichment in the neuroectoderm. Expression is enriched in early embryos, decreases during larval stages, and rises again at pupal stages (PubMed:29555755). Strongly expressed during the maternal-to-zygotic transition, a time where N6-methyladenosine (m6A) methylation of mRNAs is decreasing (PubMed:29535189). Female-specific lethality, associated with sexual transformation phenotypes (PubMed:29555755). Hemizygous males are sterile (PubMed:29555755). Sexual transformation phenotypes resemble other N6-methyladenosine (m6A) factors, such as sexual transformations, Sxl splicing defect, held-out wings, flightless flies and reduction of m6A levels (PubMed:29555755). Was named Xiong after the Chinese character for maleness. Belongs to the ZC3H13 family.