Seed dormancy loss from dry after-ripening is associated with increasing gibberellin hormone levels in Arabidopsis thaliana

Abstract

IntroductionThe seeds of many plants are dormant and unable to germinate at maturity, but gain the ability to germinate through after-ripening during dry storage. The hormone abscisic acid (ABA) stimulates seed dormancy, whereas gibberellin A (GA) stimulates dormancy loss and germination.MethodsTo determine whether dry after-ripening alters the potential to accumulate ABA and GA, hormone levels were measured during an after-ripening time course in dry and imbibing ungerminated seeds of wildtype Landsberg erecta (Ler) and of the highly dormant GA-insensitive mutant sleepy1-2 (sly1-2).ResultsThe elevated sly1-2 dormancy was associated with lower rather than higher ABA levels. Ler germination increased with 2-4 weeks of after-ripening whereas sly1-2 required 21 months to after-ripen. Increasing germination capacity with after-ripening was associated with increasing GA4 levels in imbibing sly1-2 and wild-type Ler seeds. During the same 12 hr imbibition period, after-ripening also resulted in increased ABA levels.DiscussionThe decreased ABA levels with after-ripening in other studies occurred later in imbibition, just before germination. This suggests a model where GA acts first, stimulating germination before ABA levels decline, and ABA acts as the final checkpoint preventing germination until processes essential to survival, like DNA repair and activation of respiration, are completed. Overexpression of the GA receptor GID1b (GA INSENSITIVE DWARF1b) was associated with increased germination of sly1-2 but decreased germination of wildtype Ler. This reduction of Ler germination was not associated with increased ABA levels. Apparently, GID1b is a positive regulator of germination in one context, but a negative regulator in the other.

Evaluating relationships between seed morphological traits and seed dormancy in Chenopodium quinoa Willd.

“…Dry seeds were transferred to separate microfuge tubes stored in sealed plastic storage bins in the dark at -20°C under low moisture conditions to maintain seed moisture at > 10%. Previous studies in wheat, arabidopsis, and quinoa have demonstrated that storage at -20°C is useful for preserving dormancy status at harvest maturity for short storage durations, i.e., less than 6 months, and does not to negatively impact seed germinability (Mares, 1983;Romero et al, 2018;Nelson et al, 2023).…”

Preharvest Sprouting in Quinoa: A New Screening Method Adapted to Panicles and GWAS Components

“…Future experiments looking to replicate this study could choose not to stagger the planting date and solely rely on storing the panicles at −20 • C after harvest, which has been shown to preserve dormancy status in quinoa [14,[60][61][62]. Our research aimed to have all the plants reach maturity by the same date to avoid differences in the post-harvest conditions, but it was logistically challenging to harvest all the plants at once.…”

Bet-hedging and variability in plant development: seed germination and beyond

“…Once seeds are shed from the parent plant, if they are stored in dry conditions, their level of dormancy drops in a process called dry after ripening. During this phase, ABA levels appear to remain high [ 40 ]. When seeds are then imbibed in water, ABA levels drop, but dormant seeds sustain higher ABA levels than those which go on to germinate [ 39 , 41 ].…”

“…A large network of regulatory factors centres on ABA and another hormone, giberrellic acid (GA), which promotes germination. Increases in GA biosynthesis, which are triggered upon imbibition, are important for germination to occur [ 40 , 42 , 43 ]. The signalling pathways of ABA and GA converge to oppositely regulate the activity of a set of transcriptional regulators which inhibit germination.…”