Department of Plant Protection, University of Zanjan, Zanjan, 313, Iran.
Department of Phytopathology, Institute for Sugar Beet Research, 37079, Göttingen, Germany.
Virus Genes. 2022 Dec;58(6):550-559. doi: 10.1007/s11262-022-01927-3. Epub 2022 Aug 12.
Beet curly top Iran virus (BCTIV) is a member of the genus Becurtovirus (Family Geminiviridae) with a circular single-strand DNA genome. BCTIV causes leaf curling and vein swelling symptoms in plants. However, the potential pathogenicity factor/s in BCTIV is/are not known. This study presents characterization of complementary-sense transcripts of BCTIV and the viral factors in directing the pathogenicity and hypersensitive response (HR) in Nicotiana benthamiana plants. In both local and systemic infection, splicing of the complementary transcripts of BCTIV was observed. Notably, a small number (8.3%) of transcripts were spliced to produce Rep (C1:C2) transcripts after deletion of 155 nt (position 1892-2046 from BCTIV). Expression of BCTIV genes in N. benthamiana using tobacco rattle virus (TRV)-based vector showed that Rep together with C1 are the main pathogenicity factors which cause typical viral leaf curling symptoms. In addition, the V2 caused a mild leaf curling, thickening, and asymmetric leaves, while the V1, V3, and C2 had no clear effect on the plant phenotype. Transient expression of individual viral genes showed that both the C1 and Rep trigger a HR response in N. benthamiana. The higher expression of HR marker genes, harpin-induced 1 (Hin1) and hypersensitivity-related (Hsr203JI), supported the role of C1 and Rep in HR response in plants. It is concluded that Rep and C1 are the main pathogenicity factors that also trigger HR response in plants.
甜菜曲顶病毒（BCTIV）是双生病毒科（Geminiviridae）贝科病毒属的一员，具有环状单链 DNA 基因组。BCTIV 可导致植物叶片卷曲和叶脉肿胀。然而，BCTIV 的潜在致病性因子尚不清楚。本研究对 BCTIV 的互补链转录本和病毒因子进行了鉴定，这些因子可在本氏烟植株中指导致病性和过敏性反应（HR）。在局部和系统感染中均观察到 BCTIV 互补转录本的剪接。值得注意的是，在缺失 155nt（BCTIV 位置 1892-2046）后，少数（8.3%）转录本通过剪接产生 Rep（C1：C2）转录本。使用烟草脆裂病毒（TRV）载体在本氏烟中表达 BCTIV 基因表明，Rep 与 C1 一起是导致典型病毒叶片卷曲症状的主要致病性因子。此外，V2 引起轻度叶片卷曲、增厚和不对称叶片，而 V1、V3 和 C2 对植物表型没有明显影响。单个病毒基因的瞬时表达表明，C1 和 Rep 均可在本氏烟中引发 HR 反应。HR 标记基因 Hin1 和 Hsr203JI 的高表达支持了 C1 和 Rep 在植物 HR 反应中的作用。综上所述，Rep 和 C1 是主要的致病性因子，也可在植物中引发 HR 反应。
