title: The E3 SUMO ligase AtSIZ1 functions in seed germination in Arabidopsis.
abstract: Seed germination is an important stage in the lifecycle of a plant because it determines subsequent vegetative growth and reproduction. Here, we show that the E3 SUMO ligase AtSIZ1 regulates seed dormancy and germination. The germination rates of the siz1 mutants were less than 50%, even after a short period of ripening. However, their germination rates increased to wild-type levels after cold stratification or long periods of ripening. In addition, exogenous gibberellin (GA) application improved the germination rates of the siz1 mutants to the wild-type level. In transgenic plants, suppression of AtSIZ1 caused rapid post-translational decay of SLEEPY1 (SLY1), a positive regulator of GA signaling, during germination, and inducible AtSIZ1 overexpression led to increased SLY1 levels. In addition, overexpressing wild-type SLY1 in transgenic sly1 mutants increased their germination ratios to wild-type levels, whereas the germination ratio of transgenic sly1 mutants overexpressing mSLY1 was similar to that of sly1. The germination ratios of siz1 mutant seeds in immature developing siliques were much lower than those of the wild-type. Moreover, SLY1 and DELAY OF GERMINATION 1 (DOG1) transcript levels were reduced in the siz1 mutants, whereas the transcript levels of DELLA and ABSCISIC ACID INSENSITIVE 3 (ABI3) were higher than those of the wild-type. Taken together, these results indicate that the reduced germination of the siz1 mutants results from impaired GA signaling due to low SLY1 levels and activity, as well as hyperdormancy due to high levels of expression of dormancy-related genes including DOG1.
authors.affiliation: Department of Plant Science, Research Institute for Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul, 151-921, Korea.
authors.forename: Sung-Il
authors.initials: SI
authors.lastname: Kim
authors.affiliation: Department of Plant Science, Research Institute for Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul, 151-921, Korea.
authors.forename: Jun Soo
authors.initials: JS
authors.lastname: Kwak
authors.affiliation: School of Applied Biosciences, Kyungpook National University, Daegu, 702-701, Korea.
authors.forename: Jong Tae
authors.initials: JT
authors.lastname: Song
authors.affiliation: Department of Plant Science, Research Institute for Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul, 151-921, Korea. seohs@snu.ac.kr.|Bio-MAX Institute, Seoul National University, Seoul, 151-818, Korea. seohs@snu.ac.kr.
authors.forename: Hak Soo
authors.initials: HS
authors.lastname: Seo
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000502:physiology; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D003080:Cold Temperature; D018525:Germination / Q000187:drug effects / Q000502:physiology*; D005875:Gibberellins / Q000494:pharmacology; D008025:Ligases / Q000502:physiology*; D009154:Mutation / Q000502:physiology; D057445:Plant Dormancy / Q000187:drug effects / Q000502:physiology; D030821:Plants, Genetically Modified / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D005875:Gibberellins; D019883:Alkyl and Aryl Transferases; C476121:SLY1 protein, Arabidopsis; D008025:Ligases; C502552:SIZ1 protein, Arabidopsis