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Research Project: Genetic Improvement of Wheat and Barley for Environmental Resilience, Disease Resistance, and End-use Quality

Location: Wheat Health, Genetics, and Quality Research

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

item NELSON, SVEN - Washington State University
item KANNO, YURI - Riken Institute
item SEO, MITSUNORI - Riken Institute
item Steber, Camille

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2023
Publication Date: 5/18/2023
Citation: Nelson, S., Kanno, Y., Seo, M., Steber, C.M. 2023. Seed dormancy loss through dry after-ripening may result from increasing gibberellin hormone levels. Frontiers in Plant Science. 14:1145414.

Interpretive Summary: Dormant seeds cannot germinate under favorable conditions until exposed to dormancy breaking conditions such as after-ripening during dry storage. You can consider these seeds to be in a natural state of suspended animation. This paper examines the biological program the determines when the seed should emerge from its state of suspended animation. Dormancy loss through after-ripening occurs under very dry conditions of 5-10% moisture. It is amazing that a biological process like after-ripening can occur under such conditions. This paper should the after-ripening results in increasing levels of the germination-promoting hormone gibberellin A or GA. This appears to result from increased accumulation of GA precursors and reduced turnover. We want to understand dormancy because it is an important aspect of evolutionary fitness. Moreover, seed dormancy protects crop species like wheat, barley, and quinoa from germinating on the mother plant when rain occurs before harvest.

Technical Abstract: The seeds of temperate plant species are dormant and unable to germinate at maturity, but gain the ability to germinate through after-ripening during a period of dry storage. Genetic evidence has shown that the hormone abscisic acid (ABA) stimulates seed dormancy, while gibberellin (GA) hormone stimulates dormancy loss and germination. T his study examined changes in ABA and GA hormone levels associated with after-ripening in dry and imbibing seeds, and examined whether these changes correlated to germination capacity in wild-type Landsberg erecta (Ler) and in the highly dormant GA-insensitive mutant sly1-2. After-ripening was associated with increasing GA4 levels in imbibing sly1-2 and wild-type Ler seeds. An increase in GA4 levels was even detected in dry sly1-2 seeds following a long 20 month period of after-ripening. This is the first evidence that after-ripening stimulates GA4 accumulation in wild-type Arabidopsis seeds. Contrary to expectation, an increase in ABA level was detected with after-ripening of Ler and sly1-2 seeds at 0-12 h of imbibition. GA4 levels increased and ABA increased at the same imbibition timepoints. The decrease in ABA levels detected with after-ripening in other studies was generally detected later in seed imbibition, just before germination. This supports a model where ABA levels rise during imbibition of non-dormant seeds to prevent premature germination during essential processes like DNA and membrane repair, and the initiation of transcription and translation. In this model GA4 stimulates germination before ABA levels decline during imbibition and ABA acts as a final checkpoint blocking germination until successful completion of essential processes.