Control of seed coat rupture by ABA-INSENSITIVE 5 in Arabidopsis thaliana

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In Arabidopsis, seed germination is a biphasic process involving rupture of the seed coat followed by emergence of the radicle through the micropylar endosperm. Embryo expansion results in seed coat rupture and removal of seed coat imposed dormancy with DELLA proteins blocking embryo expansion in the absence of gibberellins. Exogenous abscisic acid (ABA) treatment does not block seed coat rupture but does block radicle emergence. We used this limited effect of exogenous ABA to further investigate the mechanism by which it blocks the onset of germination marked by seed coat rupture. We show that physical nicking of the seed coat results in exogenous ABA treatment blocking both seed coat and endosperm rupture and this block requires the transcription factors ABI3 and ABI5, but not ABI4. Furthermore, we show that the repression of expression of several EXPANSIN genes (EXPA1, EXPA2, EXPA3, EXPA9 and EXPA20) by exogenous ABA requires ABI5. We conclude that ABI5 plays an important role in the ABA-mediated repression of germination through prevention of seed coat rupture and propose that this involves EXPANSIN related control of cell wall loosening.

Original languageEnglish
JournalSeed Science Research
Issue number2
Early online date12 Apr 2019
Publication statusE-pub ahead of print - 12 Apr 2019

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© Cambridge University Press 2019. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.


  • ABA
  • ABI5
  • nicking
  • testa rupture

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