Required to form the C-22 double bond in the sterol side chain. Possesses C-22 desaturase activity toward beta-sitosterol and produces stigmasterol. 5-dehydroepisterol + H(+) + NADPH + O2 = ergosta-5,7,22,24(28)-tetraen-3beta-ol + 2 H2O + NADP(+) Steroid biosynthesis; sterol biosynthesis. Very weak expression in roots and root hairs. Not detected in the root tips. Not induced by pathogen infection. Plants overexpressing CYP710A4 show higher levels of stigmasterol and lower levels of beta-sitosterol than the wild-type. Belongs to the cytochrome P450 family. Sequencing errors.