Genome Sequencing of Chinese yam (Dioscorea polystachya): analysis of PEBP gene family diversity and identification of a potential tuber inducing factor.

Abstract

Phosphatidylethanolamine-binding proteins (PEBPs) are a class of ancient plant proteins involved in flowering, seed development and storage organ formation. The FLOWERING LOCUS T subgroup was shown to be involved in the initiation of flowering and tuberization. We aimed to characterize the PEBP family in the tuber crop Chinese yam (Dioscorea polystachya) and to identify FLOWERING LOCUS T (FT) homologs potentially involved in Chinese yam tuber formation. Based on a de novo genome assembly of Chinese yam, we investigated members of the PEBP family in silico. Expression analysis of FT homologs in yam tuber tissue revealed DpFT3a as a candidate for a tuber inducing FT. We then performed functional characterization of DpFTs by localization and interaction studies, as well as constitutive overexpression in Arabidopsis thaliana and Solanum tuberosum. Analysis of the genome annotations revealed members of the PEBP-family in Chinese yams. Identified PEBPs were subjected to phylogenetic analysis and transcriptomic studies. Of the identified 9 FT homologs, DpFT3a, which was strongly expressed in yam tubers, was found to cause a severe tuberizing phenotype in transgenic potato (Solanum tuberosum cv. Desiree), indicating a role of DpFT3a in storage organ formation. We identified a Chinese yam specific FT homolog and provide strong indication for a role of this FT in tuber formation in yam as well as its potential to induce tuberous structures in potato. Our results complement the current knowledge on PEBP proteins in plants.