Slow darkening of pinto bean seed coat is associated with significant metabolite and transcript differences related to proanthocyanidin biosynthesis

Abstract

BackgroundPostharvest seed coat darkening in pinto bean is an undesirable trait resulting in a loss in the economic value of the crop. The extent of darkening varies between the bean cultivars and their storage conditions.ResultsMetabolite analysis revealed that the majority of flavonoids including proanthocyanidin monomer catechin accumulated at higher level in a regular darkening (RD) pinto line CDC Pintium than in a slow darkening (SD) line 1533–15. A transcriptome analysis was conducted to compare gene expression between CDC Pintium and 1533–15 and identify the gene (s) that may play a role in slow darkening processes in 1533–15 pinto.RNAseq against total RNA from RD and SD cultivars found several phenylpropanoid genes, metabolite transporter genes and genes involved in gene regulation or modification to be differentially expressed between CDC Pintium and 1533–15.ConclusionRNAseq analysis and metabolite data of seed coat tissue from CDC Pintium and 1533–15 revealed that the whole proanthocyanidin biosynthetic pathway was downregulated in 1533–15. Additionally, genes that encode for putative transporter proteins were also downregulated in 1533–15 suggesting both synthesis and accumulation of proanthocyanidin is reduced in SD pintos.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-4550-z) contains supplementary material, which is available to authorized users.

Carioca bean genotypes for tolerance to grain darkening by natural and accelerated methods

“…Junk-Knievel, Vandenberg and Bett (2007) suggested that grain darkening is associated with the presence of proanthocyanidins (condensed tannins) present in the tegument. According to Duwadi et al (2018), most flavonoids, including catechin monomer proanthocyanidins, accumulate at higher levels in regular darkening than slow darkening genotypes. Proanthocyanidins are oligomeric flavonoids composed primarily of catechin and epicatechin units (Duwadi et al, 2018).…”

“…According to Duwadi et al (2018), most flavonoids, including catechin monomer proanthocyanidins, accumulate at higher levels in regular darkening than slow darkening genotypes. Proanthocyanidins are oligomeric flavonoids composed primarily of catechin and epicatechin units (Duwadi et al, 2018). Table 3 shows the analysis of the environments, where it was observed that, in general, the environment that presented lighter grains was Campinas, both in the "dry" and "rainy" season.…”

“…According to Erfatpour, Navabi and Pauls (2018), polyphenolic compounds have been associated with the color and pattern of grain coverage in common beans. Slow darkening is significantly associated with reduced levels of kaempferol and polyphenol oxidase activity, which is responsible for the oxidation of polyphenols (Beninger et al, 2005;Duwadi et al, 2018).…”

Postharvest seed coat darkening in pinto bean (Phaseolus vulgaris) is regulated by Psd, an allele of the basic helix‐loop‐helix transcription factor P

“…C, untreated and UVC, treated. (b) Genotypes of SD, RD, and ND pinto bean lines and two representative SD and RD RILS from Wit-rood boonjie and 1533-15 cross showing a 3 nucleotide InDel (GAG) in exon 2 and a SNP (G to A) in exon 7 of P that associate with differences in darkening phenotype compared to 1533-15 (SD) in immature seed coat and mature seeds (both aged and non-aged; Beninger et al, 2005;Duwadi et al, 2018) provided additional support for P sd as the Sd gene, and its function in PA accumulation.…”

“…The dashed arrows represent speculative steps and multiple arrows indicate multiple steps. The corresponding transcripts (blue highlights) and metabolites (orange highlights) accumulate at higher level in developing seed coats of CDC Pintium (RD) compared to 1533-15 (SD; Duwadi et al. 2018).…”