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.