A conserved inverted repeat from rice plastome functions as an intrinsic transcription terminator

Abstract

Results from a previous rice transcription mapping and the GeSTer algorithm analysis used in this in-vestigation for rice plastid genome suggest that an inverted repeat, IRsl8, in 3′ region of the plastid rps18 gene may serve as a transcription terminator. The in vitro transcription assay showed that the transcript ending at the IRsl8 was not proc-essed by ribonucleases but terminated intrinsically in an rNTP substrate-dependent manner as demonstrated for the first time in plant gene regulation. For the poly-T tract (TTCTTTTTT) 3′-proximal to the IRsl8, the C base conver-sion to T resulting in a perfect 9 Ts can dramatically increase termination efficiency, which is a common feature of bacte-rial intrinsic termination. This study is the first case to indi-cate that a conserved inverted repeat with a poly-T tract from higher plant chloroplast contributes to transcription termination of the translation-associated rps18 gene in a manner with the intrinsic termination, probably resulting from a heritage of endosymbiosis.