Identifying Candidate Genes for Improved Nutrition in Watercress through RNA-Seq

Watercress (Nasturtium officinale R. Br.; Brassicaceae) is a peppery-flavoured leafy salad crop with a long tradition of cultivation in southern England and increasing popularity around the world. It has received much attention in recent years as one of the most nutrient dense foods and is thought to offer antioxidant and chemopreventive benefits to the consumer. These benefits are derived from the high concentrations of secondary metabolites found in the crop, including glucosinolates. Despite this evidence, watercress remains largely undeveloped with limited breeding resources and no active breeding programmes worldwide. The aim of our work is to understand the genetic basis of important nutritional and agronomic traits in watercress and use modern molecular tools to develop breeding knowledge and resources for the future. Firstly, we will outline the initial steps taken to establish a watercress breeding program at the University of Southampton. Then we will present recent work which utilized RNASeq to assemble and annotate the watercress transcriptome and differential expression analysis to characterize differences between high and low phytonutrient phenotypes. Finally, we will discuss our current efforts to expand molecular tools for this species. Our results, thus far, represent a first and important genetic resource for this understudied crop and include a catalogue of genes known to be, or potentially involved in, nutrient status as well as thousands of markers which could be employed for marker assisted selection and/or genetic mapping for nutritional traits in watercress.