MYB class transcription factors bind to the tuber-specific and sucrose-response element of a class-I patatin promoter

Abstract

Class-I patatin genes, which encode the potato storage protein patatin, are tuber specific in their expression, and several promoter elements directing the tissue-specific expression of the patatin genes have been known for long time. However, the identity of the relevant transcription factors is still unknown. In this study, we show that K box, one of the protein-binding sites in a class-I patatin gene promoter, is a novel cis-regulatory element required for the tuber-specific expression of the gene. Subsequently, we isolated K-box-binding factors by yeast one-hybrid screening. Analysis of the factors revealed that they are MYB class transcription factors, which we named TSF1–4 (tuber-specific and sucrose-inducible element-binding factors 1–4). TSFs possess transcriptional activity to various degrees, and overexpression of TSF2, which possesses the highest transcriptional activity, induced the ectopic expression of patatin genes in potato leaves. Our results strongly suggest that TSFs could play regulatory function in the expression of patatin genes in planta.