Diverse Regulations of Viral and Host Genes in Tomato Germplasms Responding to Tomato Yellow Leaf Curl Virus Inoculation

Tomato yellow leaf curl virus(TYLCV)is the dominating pathogen of tomato yellow leaf curl disease that caused severe loss to tomato production in China.In this study,we found that a TYLCV-resistant tomato line drastically reduced the accumulation of viral complementary-sense strand mRNAs but just moderately inhibited that of viral DNA and virion-sense strand mRNAs.However,two other resistant lines did not have such virus inhibition pattern.Analysis of differential expressed genes showed that the potential host defense-relevant processes varied in different resistant tomatoes,as compared to the susceptible line,suggesting a diversity of tomato TYLCV-resistance mechanisms.

Monoclonal Antibodies Against the Whitefly-Transmitted Tomato Yellow Leaf Curl Virus and Their Application in Virus Detection

Tomato yellow leaf curl virus（TYLCV）is a species of the family Geminiviridae,causing serious yield losses in tomato production.The coat protein（CP）gene of TYLCV isolate SH2 was expressed in Escherichia coli BL21（DE3）using pET-32a as the expression vector.The recombinant protein was purified through Ni＋-NTA affinity column and used to immunize BALB/c mice.Three hybridoma cell lines（2B2,2E3 and 3E10）secreting monoclonal antibodies（MAbs）against TYLCV CP were obtained by fusing mouse myeloma cells（Sp 2/0）with spleen cells from the immunized BALB/c mouse.The titers of ascitic fluids of three MAbs ranged from 10-6 to 10-7 in indirect-ELISA.Isotypes and subclasses of all the MAbs belonged to IgG1,κ light chain.Triple antibody sandwich enzyme-linked immunosorbent assay（TAS-ELISA）showed that the MAb 3E10 could react with five begomoviruses infecting tomato,while the other two（2B2 and 2E3）mainly reacted with TYLCV.TAS-ELISA was set up using the MAb 3E10,and the established method could successfully detect virus in plant sap at 1：2 560（w/v,g mL-1）.Detection of field samples showed that begomoviruses were common in tomato crops in Zhejiang Province,China.

Mapping and Candidate Gene Screening of Tomato Yellow Leaf Curl Virus Resistant Gene ty-5

To identify the inheritance pattern and perform fne mapping of ty-5 gene, P1, P2, F1, BC1 and F2 generations were obtained through a cross between CLN32120a-23 （containing ty-5 gene, P1） and S. lycopersicum Moneymaker （fully susceptible, P2）. The results showed that resistance of ty-5 gene was determined by a recessive effect. Meanwhile, it was presumed that another resistance gene might be involved in mediating the resistance to tomato yellow leaf curl virus （TYLCV）. In this study, fne mapping was used to map TYLCV resistance locus to an interval between NAC1 and TES2461 on the short arm of chromosome 4 with genetic distances of 0.5 and 0.8 cM, respectively. qRT-PCR results showed that four candidate genes, SlNAC1; LOC104229164; LOC101260925 and LOC101261508 having resistance-related expression patterns, were the likely target genes of ty-5. In addition, it was found that the codominant marker TES2461 could be used in marker-assisted selection （MAS） breeding. The fndings of this research provided the basis for future cloning of ty-5 gene as well as MAS breeding and plant resistance mechanism studies.

Development of high yield and tomato yellow leaf curl virus(TYLCV)resistance using conventional and molecular approaches:A review

Tomato(Solanum lycopersicum L.)belonging to the family Solanaceae is the second most consumed and cultivated vegetable globally.Since the ancient time of its domestication,thousands of cultivated tomato varieties have been developed targeting an array of aspects.Among which breeding for yield and yield-related traits are mostly focused.Cultivated tomato is extremely genetically poor and hence it is a victim for several biotic and abiotic stresses.Among the biotic stresses,the impact of viral diseases is critical all over tomato cultivating areas.Improvement of tomato still largely rely on conventional methods worldwide while molecular approaches,particularly Marker Assisted Selection(MAS)has become popular across the globe as a fast,low cost and precise tool which is essential in present day plant breeding.In this review paper,breeding tomato for high yield and viral disease resistance,particularly to tomato yellow leaf curl virus disease(TYLCVD)using conventional and molecular approaches will be discussed.Lining up of this set of information will be useful to those who are interested in tomato variety development with high yielding and TYLCVD resistance.

Characterization and function of Tomato yellow leaf curl virus-derived small RNAs generated in tolerant and susceptible tomato varieties

supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China （20134320120013）;the Natural Science Foundation of Hunan Province, China （14JJ3095）

Markers for Rapid Evaluation of Virus Resistance for TYLCV in Tomato, ZYMV and PRSV-W in Zucchini and LMV in Lettuce and Hybrid Seeds in Pumpkin

Screening for the source of virus resistance in horticultural plants or specific characterization as hybridization, through symptoms, requires time and depends on the weather and knowledge of plant characteristics. So, it is important to develop specific gene markers to allow rapid diagnosis by PCR. Markers were developed based on sequences homology comparison of susceptible and resistant plants provided by HORTEC SEEDS in tomato for Tomato yellow leaf curl virus (TYLCV) by the resistance gene Ty-1, in zucchini for Zucchini yellow mosaic virus (ZYMV) and Papaya ringspot virus estirpe watermelon (PRSV-W), and in lettuce for Lettuce mosaic virus (LMV). Fragments of 249 bp were amplified only by resistant plants to TYLCV as the hybrids 2648 and Aguamiel, and not for varieties as Santa Cruz or Carina. It were observed for ZYMV the amplification of 791 bp by the resistant hybrid Px7051 and not for the susceptible cultivar La Belle;for PRSV-W using the same zucchini plants the amplification of 650 bp for susceptible and 750 bp for resistant;for LMV the 421 bp amplification only for the resistant cultivar Brasil 303 and not for susceptible Babá de Verão. Finally, it was observed that primers PK47F/R were able to check the Cabotiá seed hybrids of pumpkin Jabras.

Tomato leaf curl New Delhi virus:an emerging plant begomovirus threatening cucurbit production

Tomato leaf curl New Delhi virus(ToLCNDV),a bipartite begomovirus,was first reported to infect tomato and has recently spread rapidly as an emerging disease to Cucurbitaceae crops.To date,the virus has been reported to infect more than 11 cucurbit crops,in 16 countries and regions,causing severe yield losses.In autumn 2022,ToLCNDV was first isolated from cucurbit plants in Southeastern coastal areas of China.Phylogenetic analysis established that these isolates belong to the Asian ToLCNDV clade,and shared high nucleotide identity and closest genetic relationship with the DNA-A sequence from the Chinese tomato-infecting ToLCNDV isolate(Accession no.OP356207)and the tomato New Delhi ToLCNDV-Severe isolate(Accession no.HM159454).In this review,we summarize the occurrence and distribution,host range,detection and diagnosis,control strategies,and genetic resistance of ToLCNDV in the Cucurbitaceae.We then summarize pathways that could be undertaken to improve our understanding of this emerging disease,with the objective to develop ToLCNDV-resistant cucurbit cultivars.

Chinese tomato yellow leaf curl virus--a new species of geminivirus

Chinese tomato yellow leaf curl virus (TYLCV CHI) and other geminiviruses were analysed with 20 monoclonal antibodies. It was shown that TYLCV CHI is serologically close to Chinese tabacco leaf curl virus (TbLCV CHI). The fragment of TYLCV CHI DNA including the common region (CR), N terminal of coat protein gene and AV1 gene was amplified by PCR and cloned, and its DNA sequence was determined. These results showed that TYLCV CHI is different from other known geminiviruses in the world, and is a new whitefly transmitted geminivirus.

Molecular characterization of Tomato yellow leaf curl China virus and its satellite DNA isolated from tobacco

Virus isolates, Y8, Y36 and Y38, were obtained from tobacco plants showing leaf curl symptoms in Honghe, Yunnan Province. In reactions with 14 monoclonal antibod-ies raised against Begomovirus particles, Y8, Y36 and Y38had similar antigenic reaction in TAS-ELISA as Tomato yel-low leaf curl China virus (TYLCCNV). The complete DNA-A nucleotide sequences of Y8, Y36 and Y38 were determinedand they contain 2727, 2730 and 2730 nucleotides, respec-tively. Each of the DNA-A sequences has a typical Bego-movirus genome organization encoding 6 ORFs with 2 ORFs [AV1(CP) and AV2] in virion-sense DNA and 4 ORFs (AC1to AC4) in complementary-sense DNA. Comparisons withtotal DNA-A, intergenic region and deduced amino acid se-quences of individual ORFs show that Y8, Y36 and Y38 are isolates of TYLCCNV. Satellite DNA molecules (DNAb) were found to be associated with Y8, Y36 and Y38, which consist of 1338, 1339 and 1338 nucleotides, respectively. Compari-sons show that these DNAb molecules share 98%—99% se-quence identities on nucleotide level and have a commonORF (designated C1) encoding 126 amino acids on the com-plementary strand.

Tomato yellow leaf curl virus infection of tomato does not affect the performance of the Q and ZHJ2 biotypes of the viral vector Bemisia tabaci

To better understand the etiology of begomovirus epidemics in regions under invasion we need to know how indigenous and invasive whitefly vectors respond to virus infection. We investigated both direct and indirect effects of infection with Tomato yellow leaf curl virus （TYLCV） on the performance of the invasive Q biotype and the indigenous Asian ZHJ2 biotype of whitefly Bemisia tabaci. The Q biotype performed better than the ZHJ2 biotype on either uninfected or virus-infected tomato plants. However, virus-infection of host plants did not, or only marginally affected, the performance of either biotype of whiteflies in terms of fecundity, longevity, survival, development and population increase. Likewise, association of the vectors with TYLCV did not affect fecundity and longevity of the Q or ZHJ2 biotypes on cotton, a non-host of TYLCV. These results indicate that the alien Q biotype whitefly, but not the indigenous ZHJ2 biotype, is likely to become the major vector of TYLCV in the field and facilitate virus epidemics.

AC2 and AC4 proteins of Tomato yellow leaf curl China virus and Tobacco curly shoot virus mediate suppression of RNA silencing

Tomato yellow leaf curl China virus Y10 isolate (TYLCCNV-Y10) alone could systemically infect host plants such as Nicotiana benthamiana without symptoms. In con- trast, Tobacco curly shoot virus Y35 isolate (TbCSV-Y35) alone induces leaf curl symptoms in N. benthamiana. When inoculated into transgenic N. benthamiana plants expressing GFP gene (line 16c), TYLCCNV-Y10 neither reverses the established GFP silencing nor blocks the onset of GFP si- lencing. In contrast, TbCSV-Y35 can partially reverse the established GFP silencing and block the onset of GFP silenc- ing in new leaves. In the patch co-infiltration assays, the AC2 and AC4 proteins of TYLCCNV-Y10 and TbCSV-Y35 could suppress local GFP silencing and delay systemic GFP silenc- ing, suggesting that they are suppressors of RNA silencing. Comparison of the accumulation levels of GFP mRNA in the co-infiltration patches showed that Y10 AC2 and Y35 AC2 proteins had similar efficiency for suppression of RNA si- lencing. However, Y35 AC4 protein functioned as a stronger suppressor of RNA silencing than Y10 AC4 protein. There- fore, the pathogenicity difference between TbCSV-Y35 and TYLCCNV-Y10 may be related to the functional difference in their AC4 proteins.

The novel C5 protein from tomato yellow leaf curl virus is a virulence factor and suppressor of gene silencing

Tomato yellow leaf curl virus(TYLCV)is known to encode 6 canonical viral proteins.Our recent study revealed that TYLCV also encodes some additional small proteins with potential virulence functions.The fifth ORF of TYLCV in the complementary sense,which we name C5,is evolutionarily conserved,but little is known about its expression and function during viral infection.Here,we confirmed the expression of the TYLCV C5 by analyzing the promoter activity of its upstream sequences and by detecting the C5 protein in infected cells by using a specific custom-made antibody.Ectopic expression of C5 using a potato virus X(PVX)vector resulted in severe mosaic symptoms and higher virus accumulation levels followed by a burst of reactive oxygen species(ROS)in Nicotiana benthamiana plants.C5 was able to effectively suppress local and systemic post-transcriptional gene silencing(PTGS)induced by single-stranded GFP but not double-stranded GFP,and reversed the transcriptional gene silencing(TGS)of GFP.Furthermore,the mutation of C5 in TYLCV inhibited viral replication and the development of disease symptoms in infected plants.Transgenic overexpression of C5 could complement the virulence of a TYLCV infectious clone encoding a dysfunctional C5.Collectively,this study reveals that TYLCV C5 is a pathogenicity determinant and RNA silencing suppressor,hence expanding our knowledge of the functional repertoire of the TYLCV proteome.

Function of A-Rich region in DNAβassociated with Tomato yellow leaf curl China virus

A novel type of circular single-stranded satellite DNA, known as DNAb, was recently characterized and demonstrated to be associated with monopartite begomovi-ruses. DNAb was essential for induction of characteristic symptoms in plants. DNAb has three structural features: an 115 bp highly conserved region, bC1 gene and A-Rich region. The in-frame ATG mutation of bC1 gene of Tomato yellow leaf curl China virus isolate Y10 (TYLCCNV-TY10) DNAb demonstrated that bC1 gene is required for leaf curl symptom. Here, the function of A-Rich region in TYLCCNV-Y10 DNAb was identified. When A-Rich region was deleted, the A-Rich deleted mutant was still capable of replication and systemic infection in plant, indicating that A-Rich region is not required for trans-replication of DNAb. The immunotrapping-PCR demonstrated that A-Rich de-leted mutant could be encapsidated in the coat protein en-coded by TYLCCNV-Y10 DNA-A, suggesting that A-Rich region is not related with DNAb encapsidation. However, the A-Rich region deleted mutant caused milder symptom.

There is the second virus that causes tobacco leaf curl disease (not TbLCV-CHI) in the field

Sequence analysis of virus isolation DNA of tobacco leaf curl disease shows that there is the second geminivirus (not Chinese Tobacco Leaf Curl Virus, TbLCV-CHI) that causes tobacco leaf curl disease in the field in the Guangxi Zhuang Autonomous Region, China. This virus DNA-A contains 2 734 nt. Large intergenic region (LIR) contains 269 nt, the virus sense strand contains 2 open reading frames (ORFs): AV1 (115 aa) and AV2 (coat protein gene, CP, 256 aa), and the complementary sense strand contains 4 ORFs: AC1 (replicase gene, 361 aa), AC2 (transactivator, 134 aa), ACS (134 aa) and AC4 (97 aa). The virus belongs to one kind of subgroup III gemini- viruses from old world, and could be the Chinese tomato yellow leaf curl virus (TYLCV-CHI).

Molecular variability and evolution of a natural population of tomato yellow leaf curl virus in Shanghai,China

Tomato yellow leaf curl virus （TYLCV）, belonging to the genus Begomovirus of the family Geminiviridae, is emerging as the most destructive pathogen of tomato plants. Since the first report of TYLCV in Shanghai, China in 2006, TYLCV has spread rapidly to 13 provinces or autonomous regions of China. In this study, the molecular varia- bility and evolution of TYLCV were monitored in Shanghai from its first upsurge in 2006 until 2010. Full-length genomic sequences of 26 isolates were obtained by rolling circle amplification. Sequence analysis showed that the intergenic region was the most variable, with a mean mutation rate of 4.81×10-3 nucleotide substitutions per site per year. Ge- netic differentiation was found within isolates obtained from 2006, 2009, and 2010, though a linear increase in genetic diversity over time was not evident. Whilst significant parts of TYLCV genes were under negative selection, the C4 gene embedded entirely within the C1 gene had a tendency to undergo positive selection. Our results indicate that a mechanism of independent evolution of overlapping regions could apply to the natural population of TYLCV in Shanghai, China.

果型和抗性基因协同对番茄黄化曲叶病毒带毒量的影响

以12份番茄种质为试材,其具有2类果实大小和3种不同抗性基因,通过检测番茄黄化曲叶病毒病田间抗性和带毒量指标,探索果实大小、抗病基因与田间抗性、带毒量之间的关系。结果显示,在自然传毒情况下,所有番茄材料都能检测到病毒感染。在番茄定植后28 d,小果型番茄M8(I)、M5(I)、M3(I)、M7(I)、M9(I)和M11(HR)带毒量均较低,大果型番茄M6(S)、M10(S)、M4(S)和M2(S)带毒量均较高,且小果型番茄田间发病率明显低于大果型番茄。除了Ty-1/ty-1单基因抗性不受番茄果实大小影响外,携带其他单基因或聚合基因抗性的番茄种质均与果实大小有关。在此节点上,带毒量越高抗性越弱,带毒量越低抗性越强。总体来说,在遭受番茄黄化曲叶病毒侵染时,小果型番茄田间抗性强于大果型番茄。

侵染北京、宁夏和内蒙古番茄的番茄黄曲叶病毒的鉴定和全基因组分析

为明确从北京、宁夏和内蒙古采集的15份疑似病毒感染的番茄样本是否感染番茄黄曲叶病毒(tomato yellow leaf curl virus,TYLCV),利用TYLCV的特异性引物对采集的样本进行检测,结果从8个样本中扩增到TYLCV片段,并获得了8个样本TYLCV的全长序列。序列分析发现,样本NS-1、NS-5、NS-8、NS-9、NS-13和NS-14的全长核苷酸序列与北京分离物TYLCV-BJTZ的相似性最高,达99.03%~99.42%;NS-2与陕西分离物TYLCV-JY-2的相似性最高,为99.60%;NS-7与江苏分离物TYLCV-YZ02的相似性最高,为99.35%。表明这8个TYLCV全基因组均为TYLCV的不同分离物。系统进化树分析发现,这8个TYLCV分离物与2017年鉴定的北京分离物聚成一个单独的分支,说明与北京分离物的亲缘关系最近。研究结果显示,TYLCV已经扩散到宁夏和内蒙古,在我国分布范围不断扩大。

基于DNA-BSA重测序和SSR技术的番茄ty-5基因分子标记的筛选

利用DNA-BSA重测序和SSR标记技术对番茄黄化曲叶病毒抗病基因ty-5开展定位研究。DNA-BSA重测序获得7个与番茄ty-5基因相关的侯选区域,分别位于1,4,9号染色体上,总长度为21.68Mb。利用SSR标记获得C_2at4g34700和SSR383标记,与番茄抗黄化曲叶病毒病基因ty-5紧密连锁,并且没有发现重组单株。最后,对DNA-BSA重测序和SSR标记结果联合分析,标记C_2at4g34700和SSR383位于重测序关联分析的1号和9号染色体的抗病关联区域附近。由此初步认定,这2个标记可以作为番茄抗黄化曲叶病毒病ty-5基因的分子标记。

和田地区设施番茄抗黄化曲叶病毒病的比较试验

为筛选出和田地区设施番茄高抗黄化曲叶病毒病品种,为设施番茄黄化曲叶病毒病的防治及抗病品种的选择提供依据。结果表明,供试品种均发现不同程度的黄化曲叶病毒侵染,番茄品种间株高、茎粗和叶片数随着黄化曲叶病毒发病率和病情指数的增加而呈下降趋势。叶绿素相对含量(SPAD值)、叶片净光合速率(Pn)和产量以特美特36号最高,与优拉578和东风199差异不显著,但显著高于其他处理。品种戴安娜、优拉578、东风199、澳粉1号、芬娜和艾利斯相对抗病指数为0.86~0.99,为高抗品种。从抗病性、植株性状、叶片光合参数和产量等指标进行综合分析,以品种特美特36号、东风199和优拉578表现较好,可作为新疆和田地区设施秋茬番茄抗黄化曲叶病毒病首选品种。

海南地区冬春作甜瓜病毒病病原鉴定与分析

为探明海南地区冬春作甜瓜病毒病的主要病原种类和危害情况,2022—2023年冬春季从海南甜瓜主产区采集34份疑似感染病毒病的甜瓜样品,利用高通量测序(high-throughput sequencing)和聚合酶链式反应(polymerase chain reaction,PCR)技术对甜瓜病毒病的病原种类进行鉴定和分析。结果表明:甜瓜黄斑病毒(melon yellow spot virus,MYSV)、西瓜银斑驳病毒(watermelon silver mottle virus,WSMo V)和中国南瓜曲叶病毒(squash leaf curl China virus,SLCCNV)引起的甜瓜病毒病在海南多个产区普遍发生。其中,MYSV检出率最高,为73.53%;其次为WSMo V,检出率61.76%;且呈现MYSV和WSMo V复合侵染现象,复合侵染率为47.06%。