Cap-snatching as a possible contributor to photosynthesis shut-off

Area of Science:

• Virology
• Plant Molecular Biology
• RNA Biology

Background:

• Cap-snatching is essential for transcription initiation by negative strand RNA viruses.
• The precise origin of capped RNAs used in this process by cytoplasmic-replicating viruses remains unclear.
• Processing bodies (P bodies) have been hypothesized as a potential source for these capped RNAs.

Purpose of the Study:

• To identify the host-derived cap donor sources for Tomato spotted wilt virus (TSWV) N mRNA.
• To investigate the impact of heat stress on cap-snatching in plants.
• To understand the relationship between cap-snatching and host gene expression.

Main Methods:

• High-throughput sequencing (HTS) of 5' non-viral leader sequences of TSWV N mRNAs from plants under normal and heat-stress conditions.
• Bioinformatic analysis to map sequenced leader sequences to the host genome.
• Differential gene expression analysis comparing normal and heat-stress conditions.

Main Results:

• Identified host-derived, non-viral leader sequences of TSWV N mRNA, typically 10-20 nt in length with specific cleavage site motifs.
• Mapped these sequences to 348 donor genes in the *Nicotiana tabacum* genome, predominantly involved in cellular photosynthesis.
• Observed differential expression of 19 donor genes under heat stress, suggesting a link between cap-snatching and photosynthesis regulation.

Conclusions:

• The study did not pinpoint specific cytoplasmic RNA granules as the sole cap source.
• Cap-snatching contributes to the downregulation of photosynthesis in plants, potentially leading to disease symptoms.
• This finding provides insights into virus-host interactions and the impact of viral transcription mechanisms on host metabolism.