Homologs of the Arabidopsis core abscisic acid (ABA) signaling component OPEN STOMATA1 (OST1) are best known for their role in closing stomata in angiosperm species. We recently characterized a fern OST1 homolog, GAMETOPHYTES ABA INSENSITIVE ON ANTHERDIOGEN 1 (GAIA1), which is not required for stomatal closure in ferns, consistent with physiologic evidence that shows the stomata of these plants respond passively to changes in leaf water status. Instead, gaia1 mutants reveal a critical role in ABA signaling for spore dormancy and sex determination, in a system regulated by antagonism between ABA and the gibberellin (GA)-derived fern hormone antheridiogen (A_CE). ABA and key proteins, including ABA receptors from the PYR/PYL/RCAR family and negative regulators of ABA-signaling from Group A of the type-2C protein phosphatases (PP2Cs), in addition to OST1 homologs, can be found in all terrestrial land plant lineages, ranging from liverworts that lack stomata, to angiosperms. As land plants have evolved and diversified over the past 450 million years, so too have the roles of this important plant hormone and the genes involved in its signaling and perception.

Item Type:	Refereed Article
Keywords:	abscisic acid (ABA), OST1, fern, evolution, PYL/RCAR, PP2Cs, land plants, sex determination
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the biological sciences
UTAS Author:	Sussmilch, FC (Dr Frances Sussmilch)
UTAS Author:	Brodribb, TJ (Professor Tim Brodribb)
UTAS Author:	McAdam, SAM (Dr Scott McAdam)
ID Code:	121309
Year Published:	2017
Funding Support:	Australian Research Council (DP140100666)
Web of Science® Times Cited:	16
Deposited By:	Plant Science
Deposited On:	2017-09-21
Last Modified:	2018-05-08
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