title: Tumours induced by a plant virus are derived from vascular tissue and have multiple intercellular gateways that facilitate virus movement.
abstract: Structural studies showed that tumours induced by Southern rice black-streaked dwarf virus (SRBSDV; genus Fijivirus, family Reoviridae) were highly organized, modified phloem, composed of sclerenchyma, vessels, hyperplastic phloem parenchyma and sieve elements (SEs). Only parenchyma and SEs were invaded by the virus. There was a special region that consisted exclusively of SEs without the usual companion cells and a new flexible type of intercellular gateway was observed on all SE-SE interfaces in this region. These flexible gateways significantly increased the intercellular contacts and thus enhanced potential symplastic transport in the tumour. Flexible gateways were structurally similar to compressed plasmodesmata but were able to accommodate complete SRBSDV virions (~80 nm diameter). Virions were also found in sieve-pore gateways, providing strong evidence for the movement of a virus with large virions within phloem tissue and suggesting that the unusual neovascularization of plant virus-induced tumours facilitated virus spread. A working model for the spread of tumour-inducing reoviruses in plants is presented.
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Key Laboratory of Plant Protection and Biotechnology, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
authors.forename: Li
authors.initials: L
authors.lastname: Xie
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Key Laboratory of Plant Protection and Biotechnology, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
authors.forename: Ming-Fang
authors.initials: MF
authors.lastname: Lv
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Key Laboratory of Plant Protection and Biotechnology, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China zhhengmu@tsinghua.org.cn jpchen2001@yahoo.com.cn.
authors.forename: Heng-Mu
authors.initials: HM
authors.lastname: Zhang
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Key Laboratory of Plant Protection and Biotechnology, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Key Laboratory of Plant Protection and Biotechnology, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
authors.forename: Jun-Min
authors.initials: JM
authors.lastname: Li
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, Key Laboratory of Plant Protection and Biotechnology, Ministry of Agriculture, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China zhhengmu@tsinghua.org.cn jpchen2001@yahoo.com.cn.
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Chen
mesh_terms: D055032:Electron Microscope Tomography; D046529:Microscopy, Electron, Transmission; D012275:Oryza / Q000648:ultrastructure / Q000821:virology*; D010941:Plant Tumors / Q000821:virology*; D010942:Plant Viruses / Q000502:physiology*; D012087:Reoviridae / Q000502:physiology*
keywords: Intercellular gateways; sieve elements; tumours; vascularization; virus movement.; virus-induced tumours