Poster: Seed Biology

Abs # 556: Dormancy termination of western white pine (Pinus monticola Dougl. Ex D. Don) seeds is associated with changes in ABA metabolism

Presenter:	Feurtado, J. Allan , afeurtad@sfu.ca
Authors	Feurtado, J. Allan  (A)   Ambrose, Steven J. (B)   Galka, Marek M. (B)   Nelson, Ken  (B)   Zaharia, L. Irina  (B)   Cutler, Adrian J. (B)   Ross, Andrew R.S. (B)   Abrams, Suzanne R. (B)   Kermode, Allison R. (A)
Affiliations:	(A): Department of Biological Sciences, Simon Fraser University, Burnaby, BC Canada V5A 1S6 (B): Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, SK Canada S7N 0W9

Western white pine (Pinus monticola) seeds exhibit deep dormancy at maturity and seed populations require several months of moist chilling to reach their uppermost germination capacities. Abscisic acid (ABA) and its metabolites, phaseic acid (PA), dihydrophaseic acid (DPA), 7'-hydroxy ABA (7'OH ABA) and ABA-glucose ester (ABA-GE), were quantified in western white pine seeds during dormancy breakage (moist chilling) and germination using an HPLC-tandem mass spectrometry method with multiple reaction monitoring and internal standards incorporating deuterium-labeled analogs. In the embryo and megagametophyte, ABA levels decreased significantly during moist chilling, coincident with an increase in the germination capacity of seeds. ABA catabolism occurred via several routes, depending on the stage and the seed tissue. Increases in PA and DPA levels were observed during moist chilling in both the embryo and megagametophyte. Within the embryo, 7'OH ABA and ABA-GE also accumulated during moist chilling; however, 7'OH ABA peaked early in germination. In the seed coat, ABA and metabolite levels were high in dry seeds, but declined precipitously during the pre-moist-chilling water soak to relatively low levels thereafter. Seeds which lacked a moist chilling period and were kept in warm moist conditions for 30 d (after an initial 13 d of soaking) maintained high ABA levels, while the amounts of PA, 7'OH ABA, and DPA decreased or remained at steady-state levels. Further work to assess the role of ABA and its catabolism in western white pine dormancy includes the quantification of additional metabolites, using labeled ABA analogues to determine fluxes in metabolism, and examining how the hard outer seed coat influences ABA metabolism.