BackgroundTobacco curly shoot virus (TbCSV) is a monopartite begomovirus associated with betasatellite (Tobacco curly shoot betasatellite, TbCSB), which causes serious leaf curl disease on tomato and tobacco in China. It is interesting that TbCSV induced severe upward leaf curling in Nicotiana benthamiana, but in the presence of TbCSB, symptoms changed to be downward leaf curling. However, the mechanism of interactions between viral pathogenicity, host defense, viral-betasatellite interactions and virus-host interactions remains unclear.MethodsIn this study, RNA-seq was used to analyze differentially expressed genes (DEGs) in N. benthamiana plants infected by TbCSV (Y35A) and TbCSV together with TbCSB (Y35AB) respectively.ResultsThrough mapping to N. benthamiana reference genome, 59,814 unigenes were identified. Transcriptome analysis revealed that a total of 4081 and 3196 DEGs were identified in Y35AB vs CK (control check) and Y35A vs CK, respectively. Both GO and KEGG analyses were conducted to classify the DEGs. Ten of the top 15 GO terms were enriched in both DEGs of Y35AB vs CK and Y35A vs CK, and these enriched GO terms mainly classified into three categories including biological process, cellular component and molecular function. KEGG pathway analysis indicated that 118 and 111 pathways were identified in Y35AB vs CK and Y35A vs CK, respectively, of which nine and six pathways were significantly enriched. Three major pathways in Y35AB vs CK involved in metabolic pathways, carbon metabolism and photosynthesis, while those in Y35A vs CK were related to Ribosome, Glyoxylate and dicarboxylate metabolism and DNA replication. We observed that 8 PR genes were significantly up-regulated and 44 LRR-RLK genes were significantly differentially expressed in Y35A treatment or in Y35AB treatment. In addition, 7 and 13 genes were identified to be significantly changed in biosynthesis and signal transduction pathway of brassinosteroid (BR) and jasmonic acid (JA) respectively.ConclusionsThese results presented here would be particularly useful to further elucidate the response of the host plant against virus infection.Electronic supplementary materialThe online version of this article (10.1186/s12985-018-1044-1) contains supplementary material, which is available to authorized users.

Sclerotinia sclerotiorum (Lib.) de Bary is a devastating fungal pathogen with worldwide distribution. S. sclerotiorum is a necrotrophic fungus that secretes many cell wall-degrading enzymes (CWDEs) that destroy plant’s cell-wall components. Functional analyses of the genes that encode CWDEs will help explain the mechanisms of growth and pathogenicity of S. sclerotiorum. Here, we isolated and characterized a gene SsXyl1 that encoded an endo-β-1, 4-xylanase in S. sclerotiorum. The SsXyl1 expression showed a slight increase during the development and germination stages of sclerotia and a dramatic increase during infection. The expression of SsXyl1 was induced by xylan. The SsXyl1 deletion strains produce aberrant sclerotia that could not germinate to form apothecia. The SsXyl1 deletion strains also lost virulence to the hosts. This study demonstrates the important roles of endo-β-1, 4-xylanase in the growth and virulence of S. sclerotiorum.

Geminiviruses are single-stranded circular DNA viruses that infect many plant species and cause severe economic losses worldwide (Fauquet et al., 2003;Harrison, 1985;Navas-Castillo et al., 2011). Based on the current taxonomic criteria, geminiviruses are

Begomovirus-DNA-␤ disease complexes induce different symptom phenotypes in their hosts. To investigate the genetic determinants of the phenotypic differences, Nicotiana spp. and tomato plants were inoculated with infectious clones of Tobacco curly shoot virus (TbCSV)/TbCSV DNA-␤ (TbCSB) and Tomato yellow leaf curl China virus (TYLCCNV)/TYLCCNV DNA-␤ (TYLCCNB) pseudorecombinants and showed that TYLCCNB induced characteristic vein-thickening and enation symptoms, while TbCSB only slightly exacerbated the leaf-curling symptoms, regardless of the helper virus being used. The roles of DNA-␤-encoded ␤C1 and a 430-nucleotide fragment containing the A-rich region and the putative ␤C1 promoter region of the ␤C1 gene (referred to as AP) in symptom development were further investigated by constructing hybrid satellites in which the ␤C1 coding region or AP was exchanged between the two satellite molecules. A TYLCCNB hybrid with TbCSB ␤C1 lost the ability to elicit the vein-thickening and enation phenotypes. TbCSB hybrids containing the TYLCCNB ␤C1 or AP fragment failed to induce the characteristic vein thickening and enations. A TYLCCNB hybrid having the TbCSB AP fragment produced the enations, but the number of enations was less and their sizes were reduced. Differently from the phloem-specific pattern of the TYLCCNB promoter, a full-length fragment upstream of the TbCSB ␤C1 gene confers a constitutive ␤-glucuronidase expression pattern in transgenic tobacco plants. The above results indicate that the DNA-␤-encoded ␤C1 protein is the symptom determinant, but the promoter of the ␤C1 gene has influence on symptom production.Geminiviruses are small plant viruses with circular singlestranded DNA (ssDNA) genomes that are encapsidated in unique twinned (geminate) particles. Members of the genus Begomovirus are transmitted by whiteflies (Bemisia tabaci) and infect dicotyledonous plants (42). Begomoviruses have either one or two circular ssDNA genomic components (DNA-A and DNA-B). The DNA-A component is capable of autonomous replication and encapsidation, whereas the DNA-B component encodes two proteins (BC1 and BV1) involved in movement (14). Recently, some monopartite begomoviruses have been found in association with a novel satellite DNA molecule, referred to as DNA-␤ and now known as a betasatellite (2,5,20,22,38,45). DNA-␤ is approximately half the size of the viral genomic DNA, and apart from a nonanucleotide sequence (TA ATATTAC), it has little sequence identity with viral genomic DNA. DNA-␤ depends on the helper virus for replication and encapsidation and, in turn, is required for the induction of bona fide disease symptoms. DNA-␤ bears a ␤C1 open reading frame (ORF) on the complementary-sense strand, which is conserved among distinct betasatellites in terms of position and size. Mutational analyses and constitutive expression have shown that ␤C1 is a strong pathogenicity/symptom determinant (7, 34, 39).Begomovirus-DNA-␤ disease complexes are associated with a wide range of plant species and induce different sets of sympto...