The wheat ABA hypersensitive ERA8 mutant is associated with increased preharvest sprouting tolerance and altered hormone accumulation
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Wheat preharvest sprouting (PHS) is the germination of mature grain on the mother plant when rain occurs before harvest. Higher abscisic acid (ABA) hormone levels and sensitivity are associated with higher seed dormancy and PHS tolerance. Consistent with this, the ABA hypersensitive ENHANCED RESPONSE TO ABA8 (ERA8) mutant resulted in increased dormancy and PHS tolerance in soft white spring wheat ‘Zak’. ERA8 seeds were initially less responsive to germination-rescue by the hormone gibberellin (GA). ERA8 gained GA and lost ABA sensitivity more slowly than wild-type during dormancy loss through after-ripening and cold imbibition. This study examined if increased ABA sensitivity in ERA8 likely resulted from increased ABA signaling or increased ABA hormone levels. Zak ERA8 had higher initial grain dormancy although endogenous embryo ABA levels were similar in Zak ERA8 and wild-type, suggesting that increased dormancy was due to increased ABA signaling rather than increased ABA accumulation. ABA levels declined with Zak ERA8 after-ripening, suggesting that ABA turnover is not defective. Elevated ERA8 dormancy was also associated with increased embryonic jasmonic acid-Ile and aleurone indole-3-acetic acid (IAA) levels. The possible implication that other plant hormones may influence wheat seed dormancy and germination are discussed.
KeywordsAbscisic acid Gibberellin Auxin Wheat Preharvest sprouting Seed dormancy
The authors sincerely thank Dr. Mark E. Sorrells for performing spike-wetting tests in 2008 and 2010. Thanks are due to Rehana S. Parveen and Dustan Cwick for expert assistance. Thanks are also due to the USDA-ARS field crew for planting and harvesting. A special thanks to the Garland-Campbell and Steber labs for helpful feedback on the research and manuscript.
This work was funded by the National Science Foundation’s East Asia and Pacific Summer Institute Award grant 1209878 (to K.M.T.), the Japanese Society for the Promotion of Science Summer Internship Award (to K.M.T. and M.S.), the Washington Grain Alliance (to C.M.S.), and the USDA-ARS (to C.M.S. and K.G.C.).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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