Faba Bean: Transcriptome Analysis from Etiolated Seedling and Developing Seed Coat of Key Cultivars for Synthesis of Proanthocyanidins, Phytate, Raffinose Family Oligosaccharides, Vicine, and Convicine

Abstract

Faba bean (Vicia faba L.) has been little examined from a genetic or genomic perspective despite its status as an established food and forage crop with some key pharmaceutical factors such as vicine and convicine (VC), which provoke severe haemolysis in genetically susceptible humans. We developed next-generation sequencing libraries to maximize information to elucidate the VC pathway or relevant markers as well as other genes of interest for the species. One selected cultivar, A01155, lacks synthesis of the favism-provoking factors, VC, and is low in tannin, while two cultivars, SSNS-1 and CDC Fatima, are wild-type for these factors. Tissues (5-to 6-d-old root and etiolated shoot and developing seed coat) were selected to maximize the utility and breadth of the gene expression profile. Approximately 1.2  10 6 expressed transcripts were sequenced and assembled into contigs. The synthetic pathways for phosphatidylinositol or phytate, the raffinose family oligosaccharides, and proanthocyanidin were examined and found to contain nearly a full complement of the synthetic genes for these pathways. A severe deficiency in anthocyanidin reductase expression was found in the low-tannin cultivar A01155. Approximately 5300 variants, including 234 variants specific to one of the three cultivars, were identified. Differences in expression and variants potentially related to VC synthesis were analyzed using strategies exploiting differences in expression between cultivars and tissues. These sequences should be of high utility for marker-assisted selection for the key traits vicine, convicine, and proanthocyanidin, and should contribute to the scant genetic maps available for this species. C ultivated faba bean (Vicia faba L.) is widely used as human food, especially in Europe, Northern Africa, and China. In view of its superior yield and feeding value over field pea (Pisum sativum L.) or other legumes, it is also widely used as animal feed for a variety of species, and it is one of the most effective nitrogen-fixing legumes (Bremer et al., 1988). As well, immature faba bean is a high-quality vegetable, supplying well-balanced protein and carbohydrate together with numerous antioxidants and essential vitamins. It is of particular value for lipid-restricted diets, as it contains less than 3% seed lipid, which is low in saturated fatty acids (unpublished results). As a legume suited to yield well in cooler conditions, it has potential for major expansion in Western Canada and elsewhere.The importance of faba bean resides not only in their nutritional value but also in the fact that they contain medically important components including vicine and convicine (VC) (Ray and Georges, 2010). These pyrimidine derivatives constitute a rare class of antinutritional factors almost exclusive to faba bean, although also occurring in other Vicia species. The aglycones of

VC1 catalyzes a key step in the biosynthesis of vicine from GTP in faba bean

“…1 ). A fragment of this gene, mis-annotated as reticuline oxidase-like , was previously identified among five other gene fragments based on gene expression comparison between normal- and low-vicine and convicine cultivars 11 . More recently, Khazaei et al (2017) 12 showed that a SNP coding for a silent mutation within this fragment distinguished between normal- and low-vicine and convicine cultivars in a diversity panel of 51 faba bean accessions.…”

Breeding and genomics status in faba bean (Vicia faba)

“…This study provided a useful snapshot of the functional classification and relative expression level of more abundant transcripts from the embryo transcriptome in the early to middle stages of its development. Subsequently, studies began to encompass multiple, separate inbred genotypes (Webb et al., ), as well as multiple tissues and genotypes (Ray, Bock, & Georges, ). The deepest transcriptome coverage produced has come from Illumina sequencing of a library of mixed tissues enriched with embryo transfer cells (Zhang et al., ).…”

Characterisation of Faba Bean (Vicia faba L.) Transcriptome Using RNA-Seq: Sequencing, De Novo Assembly, Annotation, and Expression Analysis

“…Several transcriptome datasets have been previously generated for faba bean, from the cultivars Windsor [53], Icarus and Ascot [22], CDC Fatima, SSNS-1, and A01155 [39], Fiord [40,54], INRA-29H and Vf136 [42], BPL10 and Albus [29], and Wizard [43]. These datasets were generated from a selection of tissues including root, shoots, seedling, embryo, seed coat, leaves, or mixed tissues.…”