Plant resistance to tomato yellow leaf curl virus is enhanced by Ba13 through modulation of RNA interference.

INTRODUCTION

Tomato yellow leaf curl virus (TYLCV), which is a typical member of the genus , causes severe crop yield losses worldwide. RNA interference (RNAi) is an important antiviral defense mechanism in plants, but whether plant beneficial microbes used as biocontrol agents would modulate RNAi in defense against TYLCV remains unclear.

METHODS

Here, we employed whole-transcriptome, bisulfite, and small RNA sequencing to decipher the possible role of Ba13 as a bacterial biocontrol agent against TYLCV in RNAi modulation.

RESULTS

Potted tomato plants were exposed to whiteflies for natural viral infection 14 days after bacterial inoculation. Compared with non-inoculated controls, the abundance of TYLCV gene in the leaves of inoculated plants decreased by 70.1% at 28 days post-infection, which mirrored the pattern observed for plant disease index. The expression of the ARGONAUTE family genes (e.g., , and ) involved in antiviral defense markedly increased by 2.44-6.73-fold following bacterial inoculation. The methylation level at CpG site 228 (in the open reading frame region of the RNA interference suppressing gene AV2) and site 461 (in the open reading frame regions of and ) was 183.1 and 63.0% higher in inoculated plants than in non-inoculated controls, respectively. The abundances of 10 small interfering RNAs matched to the TYLCV genome were all reduced in inoculated plants, accompanied by enhancement of photosystem and auxin response pathways.

DISCUSSION

The results indicate that the application of Ba13 enhances plant resistance to TYLCV through RNAi modulation by upregulating RNAi-related gene expression and enhancing viral genome methylation.