Poster: Seed Biology

Abs # 559: A gymnosperm CnABI3 gene from yellow-cedar functionally complements the ABI3 gene of Arabidopsis

Presenter:	Zeng, Ying , yzeng@sfu.ca
Authors	Zeng, Ying  (A)   Kermode, Allison R (A)
Affiliations:	(A): Simon Fraser University

ABI3/VP1 transcriptional factors regulate ABA responsive genes in developing seeds, particularly those required for reserve deposition, dormancy inception, and the acquisition of desiccation tolerance. CnABI3 of yellow-cedar (Chamaecyparis nootkatensis), a conifer species whose seeds are deeply dormant at maturity, is a homologue of the ABI3/VP1 gene of angiosperms. This gene shares many common characteristics with other ABI3/VP1 genes, yet it has unique characteristics as well. One very interesting question is whether this gymnosperm transcription factor can functionally complement the angiosperm homologue when expressed in an angiosperm species with a defective ABI3 gene. A severe Arabidopsis ABI3 null mutant abi3-6, which produces green seeds that are highly ABA insensitive, lack dormancy and are severely intolerant of water loss, served as the candidate in this study. The CnABI3 gene coding-region driven by a double 35S promoter was stably expressed in the Arabidopsis abi3-6 mutant. Visible phenotypes of seeds from transformants were restored to those of the wild-type. Sensitivities of transgenic seeds to exogenous ABA (as far as germination is concerned) increased substantially, but were somewhat lower than that of wild-type seeds, indicating only a partial restoration with respect to ABA sensitivity. Seed- and leaf-protein profiles (particularly of seed-storage proteins), desiccation tolerance and dormancy of the mature seeds and flowering time were completely restored to the wild-type. These studies reveal the degree of conservation of ABI3 functions between gymnosperms and angiosperms.