Proanthocyanidins Inhibit Seed Germination by Maintaining a High Level of Abscisic Acid in Arabidopsis thaliana^F

Abstract

Proanthocyanidins (PAs) are the main products of the flavonoid biosynthetic pathway in seeds, but their biological function during seed germination is still unclear. We observed that seed germination is delayed with the increase of exogenous PA concentration in Arabidopsis. A similar inhibitory effect occurred in peeled Brassica napus seeds, which was observed by measuring radicle elongation. Using abscisic acid (ABA), a biosynthetic and metabolic inhibitor, and gene expression analysis by real-time polymerase chain reaction, we found that the inhibitory effect of PAs on seed germination is due to their promotion of ABA via de novo biogenesis, rather than by any inhibition of its degradation. Consistent with the relationship between PA content and ABA accumulation in seeds, PA-deficient mutants maintain a lower level of ABA compared with wild-types during germination. Our data suggest that PA distribution in the seed coat can act as a doorkeeper to seed germination. PA regulation of seed germination is mediated by the ABA signaling pathway. Keywords:

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

“…This is in agreement with a report demonstrating that germination is inhibited in Arabidopsis and B. napus seeds following the application of exogenous proanthocyanidins [60]. In Arabidopsis, seed coats that are high in proanthocyanidins promote strong seed dormancy, as these are less permeable to water and promote de novo formation of the growth inhibitor, abscisic acid [60, 61]. The accelerated germination capacity in non-darkening cranberry bean seeds was correlated with an absence of proanthocyanidin content in their seed coats, but their impact on hormone-related processes is not known.…”

“…This is most likely due to the dramatic difference in proanthocyanidin content within the seed coats of these two genotypes. This is in agreement with a report demonstrating that germination is inhibited in Arabidopsis and B. napus seeds following the application of exogenous proanthocyanidins [60]. In Arabidopsis, seed coats that are high in proanthocyanidins promote strong seed dormancy, as these are less permeable to water and promote de novo formation of the growth inhibitor, abscisic acid [60, 61].…”

“…Seed germination assays were performed essentially as described previously [60]. Aged seeds (previously stored at 4 °C for 48 months) of both cranberry bean RILs were washed with 70% ( v /v) ethanol for 2 min, followed by three successive rinses with sterile water (1 min each).…”

Trans-acting small interfering RNA4: key to nutraceutical synthesis in grape development?

“…In Arabidopsis , the tasiRNA TAS4-3’-D4(−) (an antisense species four registers downstream from the miR828 trigger) targets a set of MYB transcription factors PRODUCTION OF ANTHOCYANIN PIGMENT1 (PAP1/MYB75), PAP2/MYB90 , and MYB113 that regulate the anthocyanin and lignin biosynthesis pathways [38, 39] and is inducible by phosphate starvation, sugars, and the plant hormone abscisic acid (ABA) [36, 37] important for seed development and stress responses including anthocyanin production [40, 41]. The R2R3 MYB class of DNA-binding transcription factors is the most abundant superfamily in plants (126 members in Arabidopsis ) [42] and several narrow MYB clades are targeted by miR828/ TAS4 and miR858, both of which are involved in flavonoid and lignin biosynthesis [6, 43–46].…”

“…Nutraceutical properties and biosynthesis Flavonoids (Latin: flavus , “yellow”) are secondary polyphenolic metabolites involved in many aspects of plant development, auxin transport [101], ABA biosynthesis [40], and structural reinforcement. They were called “vitamin P” (not to be confused with the current euphemism for the anti-depressants Prozac and Paxil) early in the last century, due to their effects on permeability of vascular capillaries.…”