passages.id: split_1_test_849_passage
passages.type: progene_text
passages.text: As a first step towards understanding the biosynthesis of isoprenoids that accumulate in specialized pigment glands of cotton at the molecular level , two full - length genes ( hmg1 and hmg2 ) were characterized encoding hmg-coA reductase ( HMGR ; EC 1.1.1.34 ) , the enzyme that catalyzes the formation of a key isoprenoid precursor .