Identification of promoter for adventitious root-specific gene expression from sweet potato

Since sweet potato (Ipomoea batatas) produces high yield of storage roots (SR), it is an attractive target for improving productivity. However, molecular information about sweet potato is limited. The number of SR per plants determines the yield of sweet potato. SRs develop from adventitious roots (AR). Therefore, the mechanisms responsible for the initiation and development of AR need to be elucidated to increase the productivity of sweet potato. We conducted a transcriptomic analysis between nodes containing AR primordia (ARnode) and stems using next-generation sequencing to identify AR-specific promoters. A total of 6,219 contigs exhibited stronger expression in the ARnodes than in the stems. Among them, we found that the expression of sweet potato Plant AT-rich sequenceand zinc-binding protein (IbPLATZ) transcription factors was AR-specific. We examined the promoter activity of IbPLATZ in the transgenic Arabidopsis plants. β-glucuronidase (GUS) staining showed that the IbPLATZ promoter conferred the expression of the GUS reporter gene in a root tipspecific manner. These results indicate that the IbPLATZ promoter is available for a root tip-specific foreign gene expression system in transgenic plants.