Molecular characterization and specific detection of two genetically distinguishable strains of East Asian Passiflora virus (EAPV) and their distribution in southern Japan

Transcriptome analysis of yellow passion fruit in response to cucumber mosaic virus infection

The cultivation and production of passion fruit (Passiflora edulis) are severely affected by viral disease. Yet there have been few studies of the molecular response of passion fruit to virus attack. In the present study, RNA-based transcriptional profiling (RNA-seq) was used to identify the gene expression profiles in yellow passion fruit (Passiflora edulis f. flavicarpa) leaves following inoculation with cucumber mosaic virus (CMV). Six RNA-seq libraries were constructed comprising a total of 42.23 Gb clean data. 1,545 differentially expressed genes (DEGs) were obtained (701 upregulated and 884 downregulated). Gene annotation analyses revealed that genes associated with plant hormone signal transduction, transcription factors, protein ubiquitination, detoxification, phenylpropanoid biosynthesis, photosynthesis and chlorophyll metabolism were significantly affected by CMV infection. The represented genes activated by CMV infection corresponded to transcription factors WRKY family, NAC family, protein ubiquitination and peroxidase. Several DEGs encoding protein TIFY, pathogenesis-related proteins, and RNA-dependent RNA polymerases also were upregualted by CMV infection. Overall, the information obtained in this study enriched the resources available for research into the molecular-genetic mechanisms of the passion fruit/CMV interaction, and might provide a theoretical basis for the prevention and management of passion fruit viral disease in the field.

Molecular characterization and complete genome of alstroemeria mosaic virus (AlMV)

Even though alstroemeria mosaic virus (AlMV) is one of the most important viruses affecting alstroemeria plants, its genome is only partially available in public sequence databases. High throughput sequencing (HTS) of RNA from alstroemeria plants with symptoms of mosaic and streaking, collected in Lasso-Ecuador, indicated the presence of AlMV and lily symptomless virus. In this study, we aimed to assemble and characterize the complete genome sequence of AlMV. Reads from Illumina sequencing of ribosomal RNA-depleted total RNA were assembled into contigs that were mapped to the sunflower chlorotic mottle virus genome, revealing the 9774 [corrected] bp complete genome sequence of AlMV. Multiple sequence alignment of the AlMV polyprotein with close homologs allowed the identification of ten mature proteins P1, HC-Pro, P3, 6K1, CI, 6K2, NIa-VPg, NIa-Pro, NIb and CP. Furthermore, several potyvirus motifs were identified in the AlMV polyprotein including those related to potyvirus aphid transmission ³³⁴KMTC³³⁷, ⁵⁹²PTK⁵⁹⁴ and ²⁸⁰⁰DAG²⁸⁰². Phylogenetic analysis based in the polyprotein showed that AlMV belongs to the potato virus Y clade and its closest relative is sunflower ring blotch virus. This study describes the first complete genome of AlMV and its placement within the genus Potyvirus, providing valuable information for future studies on this economically important virus.

Cucumber mosaic virus infection modulated the phytochemical contents of Passiflora edulis

Cucumber mosaic virus (CMV) caused huge agricultural impact on Passiflora edulis. However, the interactions between CMV and P. edulis are poorly unknown, which lead to lack of prevention and control measures. In this study, we identified the infection of CMV in P. edulis through modern small RNA sequencing (sRNA-seq) technology combined with traditional electron microscope and polymerase chain reaction (PCR) methods. We also confirmed CMV infection adversely affected or modulated the contents of phytochemicals and further injured the development of P. edulis; inversely, P. edulis modulated its resistance to CMV stress by increasing the levels of secondary metabolites and the activities of antioxidant enzymes components. This is of significant importance to understand the interaction between virus infection and plant host.

Identification of Telosma mosaic virus infection in Passiflora edulis and its impact on phytochemical contents

Background

Viral disease has become the most severe constraint for the cultivation and production of Passiflora edulis in China. The infection of Telosma mosaic virus (TeMV), a potyvirus, and its effects on the phytochemical components of P. edulis remain largely unknown in China.

Methods

P. edulis plants showing distorted leaves and severe mosaic skin on green fruit were identified with TeMV infection through traditional transmission electron microscopy, RT-PCR and modern small RNA sequencing (sRNA-seq) platform. The contents of phytochemical components and the activities of antioxidative enzymes were compared between virus-infected and virus-free P. edulis to confirm the effects of TeMV infection on host plant.

Results

Firstly, approximately 700 nm linear virus particles, representing TeMV, were detected in infected P. edulis fruits and leaves with Electron microscopy. Partial coat protein genes of TeMV were successfully amplified by RT-PCR in infected P. edulis leaves and fruits but not in healthy plants. Abundant small interference RNAs (siRNAs) sequences, showing several characterizations, were specifically generated from the TeMV genome in infected plant fruits by sRNA-seq platform. Furthermore, fruit length, fruit thickness (wideness) and fruit weight decreased significantly due to TeMV infection. The levels of total protein and total sugar increased significantly; however, the level of total fat, total acid and vitamin C decreased obviously after TeMV infection. The level of total phenols, a secondary metabolite, was obviously higher in TeMV-infected than TeMV-free P. edulis fruit. The activities of superoxide dismutases (SOD) and catalases (CAT) obviously increased in TeMV-infected in comparison with healthy P. edulis fruit.

Conclusions

TeMV infection adversely affected the development of P. edulis fruits, differently and selectively modulated the phytochemical components of P. edulis fruits. In turn, P. edulis plants enhanced their tolerance to the stress of TeMV infection by increasing the secondary metabolite level and the antioxidative capacity. This is of significant importance to understand the effects of TeMV infection on the biochemical changes and the antioxidant defense mechanism in P. edulis.

Structure and Noncanonical Activities of Coat Proteins of Helical Plant Viruses

The main function of virus coat protein is formation of the capsid that protects the virus genome against degradation. However, besides the structural function, coat proteins have many additional important activities in the infection cycle of the virus and in the defense response of host plants to viral infection. This review focuses on noncanonical functions of coat proteins of helical RNA-containing plant viruses with positive genome polarity. Analysis of data on the structural organization of coat proteins of helical viruses has demonstrated that the presence of intrinsically disordered regions within the protein structure plays an important role in implementation of nonstructural functions and largely determines the multifunctionality of coat proteins.

Complete nucleotide sequence of a new isolate of passion fruit woodiness virus from Western Australia

We determined the complete genome sequence of the passion fruit woodiness virus Gld-1 isolate (PWV-Gld-1) from Australia and compared it with that of PWV-MU-2, another Australian isolate of PWV. The genomes shared high sequence identity in both the complete nucleotide sequence and the ORF amino acid sequence. All of the cleavage sites of each protein were identical to those of MU-2, and the sequence identity for the individual proteins ranged from 97.2 % to 100.0 %. However, the 5' untranslated region (5'UTR) of the Gld-1 isolate shared only 46.8 % sequence identity with that of PWV-MU-2 and was 177 nucleotides shorter. Re-sequencing of the 5'UTR of MU-2 revealed that the 5' end of the original sequence includes an artifact generated by deep sequencing.