The biosynthetic pathway of potato solanidanes diverged from that of spirosolanes due to evolution of a dioxygenase

Potato (Solanum tuberosum), a worldwide major food crop, produces the toxic, bitter tasting solanidane glycoalkaloids alpha -solanine and alpha -chaconine. Controlling levels of glycoalkaloids is an important focus on potato breeding. Tomato (Solanum lycopersicum) contains a bitter spirosolane glycoalkaloid, alpha -tomatine. These glycoalkaloids are biosynthesized from cholesterol via a partly common pathway, although the mechanisms giving rise to the structural differences between solanidane and spirosolane remained elusive. Here we identify a 2-oxoglutarate dependent dioxygenase, designated as DPS (Dioxygenase for Potato Solanidane synthesis), that is a key enzyme for solanidane glycoalkaloid biosynthesis in potato. DPS catalyzes the ring-rearrangement from spirosolane to solanidane via C-16 hydroxylation. Evolutionary divergence of spirosolane-metabolizing dioxygenases contributes to the emergence of toxic solanidane glycoalkaloids in potato and the chemical diversity in Solanaceae. One goal of potato breeding is to reduce the accumulation of toxic solanidane glycoalkaloids. Here the authors show that potato DPS, a 2-oxoglutarate dependent dioxygenase, catalyzes ring rearrangement of a biosynthetic precursor to differentiate solanidanes from spirosolanes that are found in other solanaceous plants.