Small RNA deep sequencing reveals the presence of multiple viral infections in cucurbit crops in Guangdong,China

Viral diseases are among the most critical damaging factors that impose a global threat to the cucurbit industry.China is the world’s leading country for the production and consumption of cucurbits.Guangdong,a province in southern China dominated by the tropical and subtropical climate,favors the survival of different plant viruses and their vectors.Five main cucurbit crops showing various disease symptoms were surveyed and collected to identify viruses infecting cucurbits in Guangdong during 2018–2020.In the field,the incidence ranged from 5-30%,or even 60-100% in the case of severely infected cucurbits.A total of 357 symptomatic samples were collected and subsequently screened for cucurbit viruses by small RNA deep sequencing and assembly(sRSA).Seventeen virus species belonging to 10 genera were identified in the five main cucurbit crops.The most common viruses were papaya ringspot virus(PRSV;Potyvirus),zucchini tigre mosaic virus(ZTMV;Potyvirus),zucchini yellow mosaic virus(ZYMV;Potyvirus),and watermelon silver mottle virus(WSMoV;Orthotospovirus),with infection rates of 24.4,19.0,17.1,and 14.3%,respectively.Notably,the most prevalent viruses were melon yellow spot orthotospovirus(MYSV)in cucumber,PRSV in squash,cucumber green mottle mosaic virus(CGMMV;Tobamovirus)in bottle gourd,WSMoV in white gourd,and ZYMV in luffa.Mixed infections were prevalent,and the types of mixed infections varied substantially in different cucurbit crops.Moreover,the full-length nucleotide sequences of watermelon green mottle mosaic virus(WGMMV),CGMMV,and watermelon virus A(WVA;Wamavirus)identified in bottle gourd were cloned and analyzed.This study is the first reporting WGMMV infecting bottle gourd in China mainland.In summary,the results demonstrate that in Guangdong,the most prevalent viruses belong to potyviruses,orthotospoviruses,and tobamoviruses groups.The findings will facilitate agricultural researchers and farmers to plan and implement effective disease control strategies aiming at timely detection and management of cucurbit-infecting viral pathogens.

Obstructor,a Frankliniella occidentalis protein,promotes transmission of tomato spotted wilt orthotospovirus

Tomato spotted wilt orthotospovirus(TSWV)causes substantial economic losses to vegetables and other crops.TSWV is mainly transmitted by thrips in a persistent and proliferative manner,and its most efficient vector is the western flower thrips,Frankliniella occidentalis(Pergande).In moving from the thrips midgut to the salivary glands in preparation for transmission,the virions must overcome multiple barriers.Although several proteins that interact with TSWV in thrips have been characterized,we hypothesized that additional thrips proteins interact with TSWV and facilitate its transmission.In the current study,67 F occidentalis proteins that interact with GN(a structural glycoprotein)were identified using a split-ubiquitin membrane-based yeast 2-hybrid(MbY2H)system.Three proteins,apolipoprotein-D(ApoD),orai-2-like(Orai),and obstructor-E-like isoform X2(Obst),were selected for further study based on their high abundance and interaction strength;their interactions with Gn were confirmed by MbY2H,yeastβ-galactosidase and luciferase complementation assays.The relative expressions of ApoD and Orai were significantly down-regulated but that of Obst was significantly up-regulated in viruliferous thrips.When interfering with Obst in larval stage,the TSWV acquisition rate in 3 independent experiments was significantly decreased by 26%,40%,and 35%,respectively.In addition,when Obst was silenced in adults,the virus titer was significantly decreased,and the TSWV transmission rate decreased from 66.7%to 31.9%using the leaf disk method and from 86.67%to 43.33%using the living plant method.However,the TSWV acquisition and transmission rates were not affected by interference with the ApoD or Orai gene.The results indicate that Obst may play an important role in TSWV acquisition and transmission in Frankliniella occidentalis.

云南省主要烟区正番茄斑萎病毒属(Orthotospovirus)病毒的调查和检测

2014年2月至2018年7月间从云南文山、昭通、楚雄、曲靖、玉溪、昆明、红河、大理和保山等州市烟区的烟株及烟田周边作物和田间杂草采集疑似感染正番茄斑萎病毒属(Orthotospovirus)病毒的566个样品。通过ELISA血清学检测、分子生物学检测等方法,对该566个样品进行了系统检测检测结果发现Orthotospovirus属病毒已在云南烟区广泛分布,但危害以番茄斑萎病毒(Tomato spotted wilt virus,TSWV)为主,检出率为43.88%,番茄环纹斑点病毒(Tomato zonate spot virus,TZSV)为辅,检出率为27.87%。结果同时表明云南烟区马铃薯、辣椒、番茄、鸢尾、鬼针草等为烟草TSWV和TZSV的重要中间寄主。该研究阐明了云南烟草斑萎病的危害和分布特点,为下一步制定针对该属病毒的防治措施奠定了良好基础。