Proanthocyanidin accumulation and transcriptional responses in the seed coat of cranberry beans (Phaseolus vulgaris L.) with different susceptibility to postharvest darkening

BMC Plant Biology

Research Article

Seth Munholland¹  William L. Crosby¹  Anjali Silva²  Sanjeena Subedi³  Lewis Lukens⁴  Gale G. Bozzo⁴  K. Peter Pauls⁴  José A. Freixas Coutin⁴ 

[1] Department of Biological Sciences, University of Windsor, 401 Sunset Ave, N9B 3P4, Windsor, ON, Canada;Department of Mathematics and Statistics, University of Guelph, 50 Stone Rd E., N1G 2W1, Guelph, ON, Canada;Department of Mathematics and Statistics, University of Guelph, 50 Stone Rd E., N1G 2W1, Guelph, ON, Canada;Present address: Department of Mathematical Sciences, Binghamton University (State University of New York), 4440 Vestal Parkway E., 13902, Binghamton, New York, USA;Department of Plant Agriculture, University of Guelph, 50 Stone Rd E., N1G 2W1, Guelph, ON, Canada;

关键词: Anthocyanidin reductase;    Phaseolus vulgaris;    Proanthocyanidin;    RNA-seq;    Seed coat darkening;    Transcriptome;   

DOI  :  10.1186/s12870-017-1037-z

 received in 2016-11-15, accepted in 2017-05-12,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundEdible dry beans (Phaseolus vulgaris L.) that darken during postharvest storage are graded lower and are less marketable than their non-darkened counterparts. Seed coat darkening in susceptible genotypes is dependent upon the availability of proanthocyanidins, and their subsequent oxidation to reactive quinones. Mature cranberry beans lacking this postharvest darkening trait tend to be proanthocyanidin-deficient, although the underlying molecular and biochemical determinants for this metabolic phenomenon are unknown.ResultsSeed coat proanthocyanidin levels increased with plant maturation in a darkening-susceptible cranberry bean recombinant inbred line (RIL), whereas these metabolites were absent in seeds of the non-darkening RIL plants. RNA sequencing (RNA-seq) analysis was used to monitor changes in the seed coat transcriptome as a function of bean development, where transcript levels were measured as fragments per kilobase of exon per million fragments mapped. A total of 1336 genes were differentially expressed between darkening and non-darkening cranberry bean RILs. Structural and regulatory genes of the proanthocyanidin biosynthesis pathway were upregulated in seed coats of the darkening RIL. A principal component analysis determined that changes in transcript levels for two genes of unknown function and three proanthocyanidin biosynthesis genes, FLAVANONE 3-HYDROXYLASE 1, DIHYDROFLAVONOL 4-REDUCTASE 1 and ANTHOCYANIDIN REDUCTASE 1 (PvANR1) were highly correlated with proanthocyanidin accumulation in seed coats of the darkening-susceptible cranberry bean RIL. HPLC-DAD analysis revealed that in vitro activity of a recombinant PvANR1 was NADPH-dependent and assays containing cyanidin yielded epicatechin and catechin; high cyanidin substrate levels inhibited the formation of both of these products.ConclusionProanthocyanidin oxidation is a pre-requisite for postharvest-related seed coat darkening in dicotyledonous seeds. In model plant species, the accumulation of proanthocyanidins is dependent upon upregulation of biosynthetic genes. In this study, proanthocyanidin production in cranberry bean seed coats was strongly associated with an increase in PvANR1 transcripts during seed maturation. In the presence of NADPH, PvANR1 converted the physiologically relevant substrate cyanidin to epicatechin and catechin.

【 授权许可】

CC BY   
© The Author(s). 2017