Poster: Hormones
Abs #
609: The expression and its role of AtNCED2 gene, encoding 9-cis-epoxycarotenoid dioxygenase, a key enzyme in ABA biosynthesis in Arabidopsis
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Presenter: |
Hobo, Tokunori , hobo@rtc.riken.go.jp |
Authors | Hobo, Tokunori (A) Iuchi, Satoshi (A) Kobayashi, Masatomo (B) Shinozaki, Kazuko Yamaguchi (C) Alonso, Jose (D) Ecker, Joseph R. (D) Shinozaki, Kazuo (A) | | Affiliations: |
(A): RIKEN Tsukuba Institute
(B): RIKEN BioResource Center
(C): Biological Resources Division, Japan International Research Center for Agricultural Science (JIRCAS)
(D): The Salk Institute for Biological Studies
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Two-major roles of the phytohormone abscisic acid (ABA) are known. First, ABA mediates responses of plants to environmental stress, such as high salinity, drought, and low temperature. Second, ABA is required for key events during seed maturation, which include accumulation of storage proteins and other reserve materials, acquisition of desiccation tolerance, arrest of embryonic development, and achievement of dormancy. In ABA biosynthesis, oxidative cleavage is the first committed reaction and is believed to the key regulatory step. The Vp14 gene encoding the key step enzyme, a 9-cis-epoxycarotenoid dioxygenase (NCED) was cloned from a mutant of Zea mays with reduced seed dormancy.
We have cloned genes homologous to Vp14 from Arabidopsis thaliana, AtNCED1, AtNCED2, AtNCED3, AtNCED4, AtNCED6 and AtNCED9. In the previous study, we showed that the overexpression of AtNCED3 gene in Arabidopsis thaliana increases abcisic acid level and enhances drought tolerance (Iuchi et al., Plant Journal (2001) 27, 325-334). In the present study, we have characterized expression and formation of the AtNCED2 gene. The AtNCED2 is expressed in silique tissue during seed maturation. And in transgenic plants containing the AtNCED2 promoter::GUS fusion gene, the GUS activity was obseved in embryo tissue. Then, we obtained the atnced2 knockout mutant from Salk T-DNA insertion line to perform loss-of-function analysis. We discuss the relationships between the atnced2 mutant phenotype and the expression of AtNCED2 gene and other AtNCEDs genes affecting the mutant phenotype.
