title: Scopoletin is a phytoalexin against Alternaria alternata in wild tobacco dependent on jasmonate signalling.
abstract: Alternaria alternata (tobacco pathotype) is a necrotrophic fungus causing severe losses in Nicotiana species by infection of mature leaves. Similar to what has been observed in cultivated tobacco, N. tabacum, young leaves of wild tobacco, N. attenuata, were more resistant to A. alternata than mature leaves, and this was correlated with stronger blue fluorescence induced after infection. However, the nature of the fluorescence-emitting compound, its role in defence, and its regulation were not clear. Silencing feruloyl-CoA 6'-hydroxylase 1 (F6'H1), the gene encoding the key enzyme for scopoletin biosynthesis, by virus-induced gene silencing (VIGS) revealed that the blue fluorescence was mainly emitted by scopoletin and its β-glycoside form, scopolin. Further analysis showed that scopoletin exhibited strong antifungal activity against A. alternata in vitro and in vivo. Importantly, jasmonic acid (JA) levels were highly elicited in young leaves but much less in mature leaves after infection; and fungus-elicited scopoletin was absent in JA-deficient plants, but was largely restored with methyl jasmonate treatments. Consistent with this, plants strongly impaired in JA biosynthesis and perception were highly susceptible to A. alternata in the same way scopoletin/scopolin-depleted VIGS F6'H1 plants. Furthermore, silencing MYC2, a master regulator of most JA responses, reduced A. alternata-induced NaF6'H1 transcripts and scopoletin. Thus, it is concluded that JA signalling is activated in N. attenuata leaves after infection, which subsequently regulates scopoletin biosynthesis for the defence against A. alternata partly through MYC2, and higher levels of scopoletin accumulated in young leaves account for their strong resistance.
authors.affiliation: Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Lanhei Road 132, 650201, Kunming, China.
authors.forename: Huanhuan
authors.initials: H
authors.lastname: Sun
authors.affiliation: Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Lanhei Road 132, 650201, Kunming, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China.
authors.forename: Baoqin
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Yunnan Academy of Tobacco Agricultural Science, Yuantong Street 33, 650031, Kunming, China.
authors.forename: Junhong
authors.initials: J
authors.lastname: Ma
authors.affiliation: Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Lanhei Road 132, 650201, Kunming, China.
authors.forename: Christian
authors.initials: C
authors.lastname: Hettenhausen
authors.affiliation: Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Lanhei Road 132, 650201, Kunming, China.
authors.forename: Guoyan
authors.initials: G
authors.lastname: Cao
authors.affiliation: Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Lanhei Road 132, 650201, Kunming, China.
authors.forename: Guiling
authors.initials: G
authors.lastname: Sun
authors.affiliation: Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Lanhei Road 132, 650201, Kunming, China.
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Wu
authors.affiliation: Key Laboratory of Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Lanhei Road 132, 650201, Kunming, China jinsongwu@mail.kib.ac.cn.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Wu
mesh_terms: D000528:Alternaria / Q000502:physiology*; D003374:Coumarins / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism*; D005960:Glucosides / Q000378:metabolism; D054884:Host-Pathogen Interactions; D054883:Oxylipins / Q000378:metabolism*; D012603:Scopoletin / Q000378:metabolism*; D012717:Sesquiterpenes / Q000378:metabolism; D014026:Nicotiana / Q000276:immunology / Q000378:metabolism / Q000382:microbiology*; D000094162:Phytoalexins
chemical_list: D003374:Coumarins; D003517:Cyclopentanes; D005960:Glucosides; D054883:Oxylipins; D012717:Sesquiterpenes; C417572:scopolin; C011006:jasmonic acid; D012603:Scopoletin; D000094162:Phytoalexins
keywords: Alternaria alternata; MYC2; Nicotiana attenuata; feruloyl-CoA 6ʹ -hydroxylase 1 (F6ʹH1); jasmonic acid (JA); scopoletin; virus-induced gene silencing (VIGS).