Practice question

FACKEL encodes sterol C-14 reductase integral to phytosterol and brassinosteroid biosynthetic pathway converting 4α-methylsterol intermediates like foliasterol into functional bulk sterols sitosterol, campesterol, and brassinolide. Sterols govern membrane fluidity, lipid raft organization, and polar targeting of PIN auxin carriers and cellulose synthases. fackel-J79 dwarf mutants resemble brassinosteroid-deficient mutants yet additionally exhibit severe embryonic patterning defects: enlarged, fused, or supernumerary cotyledons, ectopic shoot meristems, and stunted roots. This demonstrates sterol composition profoundly influences embryonic patterning and meristem programming beyond mere brassinosteroid hormone supply alone.