The plastid genome of mycoheterotrophic monocot petrosavia stellaris exhibits both gene losses and multiple rearrangements

Abstract

Plastid genomes of nonphotosynthetic plants represent a perfect model for studying evolution under relaxed selection pressure. However, the information on their sequences is still limited. We sequenced and assembled plastidgenome of Petrosavia stellaris, a rare mycoheterotrophic monocot plant. After orchids, Petrosavia represents only the second family of nonphotosynthetic monocots to have its plastidgenome examined. Several unusual features were found: retention of the ATP synthasegenes and rbcL gene; extensive gene order rearrangement despite a relative lack of repeat sequences; an unusually short inverted repeat region that excludes most of the rDNA operon; and a lack of evidence for accelerated sequence evolution. Plastome of photosynthetic relative of P. stellaris, Japonolirion osense, has standard gene order and does not have the predisposition to inversions. Thus, the rearrangements in the P. stellaris plastome are the most likely associated with transition to heterotrophic way of life.