title: Reactive Oxygen Species Generated by NADPH Oxidases Promote Radicle Protrusion and Root Elongation during Rice Seed Germination.
abstract: Seed germination is a complicated biological process that requires regulation through various enzymatic and non-enzymatic mechanisms. Although it has been recognized that reactive oxygen species (ROS) regulate radicle emergence and root elongation in a non-enzymatic manner during dicot seed germination, the role of ROS in monocot seed germination remains unknown. NADPH oxidases (NOXs) are the major ROS producers in plants; however, whether and how NOXs regulate rice seed germination through ROS generation remains unclear. Here, we report that diphenyleneiodinium (DPI), a specific NOX inhibitor, potently inhibited embryo and seedling growth-especially that of the radicle and of root elongation-in a dose-dependent manner. Notably, the DPI-mediated inhibition of radicle and root growth could be eliminated by transferring seedlings from DPI to water. Furthermore, ROS production/accumulation during rice seed germination was quantified via histochemistry. Superoxide radicals (O₂-), hydrogen peroxide (H₂O₂) and hydroxyl radicals (•OH) accumulated steadily in the coleorhiza, radicle and seedling root of germinating rice seeds. Expression profiles of the nine typical NOX genes were also investigated. According to quantitative PCR,OsNOX5,7and9were expressed relatively higher. When seeds were incubated in water,OsNOX5expression progressively increased in the embryo from 12 to 48 h, whereasOsNOX7and9expressions increased from 12 to 24 h and decreased thereafter. As expected, DPI inhibits the expression at predetermined time points for each of these genes. Taken together, these results suggest that ROS produced by NOXs are involved in radicle and root elongation during rice seed germination, andOsNOX5,7and9could play crucial roles in rice seed germination. These findings will facilitate further studies of the roles of ROS generated by NOXs during seed germination and seedling establishment and also provide valuable information for the regulation of NOX family gene expression in germinating seeds of monocot cereals.
authors.affiliation: Argo-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China. liwy1023@foxmail.com.
authors.forename: Wen-Yan
authors.initials: WY
authors.lastname: Li
authors.affiliation: Argo-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China. bxchen@agrogene.ac.cn.
authors.forename: Bing-Xian
authors.initials: BX
authors.lastname: Chen
authors.affiliation: Argo-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China. chenzhongjian@agrogene.ac.cn.
authors.forename: Zhong-Jian
authors.initials: ZJ
authors.lastname: Chen
authors.affiliation: Argo-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China. gaoyintao@agrogene.ac.cn.
authors.forename: Yin-Tao
authors.initials: YT
authors.lastname: Gao
authors.affiliation: Argo-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China. chenzhuang@agrogene.ac.cn.
authors.forename: Zhuang
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Argo-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China. liujun@agrogene.ac.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
mesh_terms: D056625:Endosperm / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D018525:Germination / Q000187:drug effects / Q000235:genetics; D006861:Hydrogen Peroxide / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D009861:Onium Compounds / Q000494:pharmacology; D012275:Oryza / Q000187:drug effects / Q000196:embryology* / Q000235:genetics; D009195:Peroxidase / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000235:genetics*; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors; D014867:Water / Q000378:metabolism
chemical_list: D009861:Onium Compounds; D017382:Reactive Oxygen Species; D014867:Water; D013481:Superoxides; C007517:diphenyleneiodonium; D006861:Hydrogen Peroxide; D009195:Peroxidase; D019255:NADPH Oxidases
keywords: NADPH oxidases; Oryza sativa; gene expression; radicle and root elongation; reactive oxygen species (ROS); seed germination