AUTHOR=Nelson Sven K. , Kanno Yuri , Seo Mitsunori , Steber Camille M. 

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

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1145414

DOI=10.3389/fpls.2023.1145414

ISSN=1664-462X

ABSTRACT=<sec><title>Introduction</title><p>The 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.</p></sec><sec><title>Methods</title><p>To 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 <italic>erecta</italic> (L<italic>er</italic>) and of the highly dormant GA-insensitive mutant <italic>sleepy1-2</italic> (<italic>sly1-2</italic>).</p></sec><sec><title>Results</title><p>The elevated <italic>sly1-2</italic> dormancy was associated with lower rather than higher ABA levels. L<italic>er</italic> germination increased with 2-4 weeks of after-ripening whereas <italic>sly1-2</italic> required 21 months to after-ripen. Increasing germination capacity with after-ripening was associated with increasing GA<sub>4</sub> levels in imbibing <italic>sly1-2</italic> and wild-type L<italic>er</italic> seeds. During the same 12 hr imbibition period, after-ripening also resulted in increased ABA levels.</p></sec><sec><title>Discussion</title><p>The 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 <italic>GID1b</italic> (<italic>GA INSENSITIVE DWARF1b</italic>) was associated with increased germination of <italic>sly1-2</italic> but decreased germination of wildtype L<italic>er.</italic> This reduction of L<italic>er</italic> germination was not associated with increased ABA levels. Apparently, <italic>GID1b</italic> is a positive regulator of germination in one context, but a negative regulator in the other.</p></sec>