Abstract

Cellular Dicer-like RNases target viroids or their double-stranded derivatives for degradation, generating 21-24 nt viroid-derived small RNAs (vd-sRNAs), which are incorporated into Argonaute proteins and guide them for sequence-specific cleavage of viroid and host mRNAs. Here, the involvement of these molecular pathways in pathogenesis has been investigated in tomato and N. benthamiana plants infected by potato spindle tuber viroid (PSTVd), a nuclear-replicating viroid causing similar symptoms (leaf curling and stunting) in both hosts.Materials and methods: Both vd-sRNAs and host microRNAs (miRNAs) were identified and quantified by high-throughput sequencing, while their potential mRNA targets were uncovered by degradome analyses. The results were validated by 5'-RML-RACE and RT-qPCR.Results: About one hundred tomato mRNAs potentially targeted for degradation by vd-sRNA were identified in the degradome. However, comparisons of data from biological replicates of healthy and infected samples reduced the potential mRNAs targets to only eight, mostly coding for proteins involved in development. RACE experiments validated these results, but RT-qPCR showed that only four of the eight mRNAs actually accumulated at lower levels in the PSTVd-infected tomato. Interestingly, comparative degradome analyses in PSTVd-infected N. benthamiana failed to uncover homologous gene (s) potentially mediating the common symptoms induced by PSTVd in this host and in tomato. Moreover, no significant modifications in the accumulation of miRNAs and their cleaved targeted mRNAs were observed in the PSTVd-infected tomato and N. benthamiana plants with respect to their healthy controls. Conclusions: This study showed that: i) cleavage of the mRNAs targeted by vd-sRNAs is not necessarily associated with the down-regulation of the corresponding gene; ii) the common symptoms induced by PSTVd in tomato and N. benthamiana do not seem to be directly linked to the effect of vd-sRNAs and/or miRNAs on host gene regulation. The implications of these findings on the mechanism of PSTVd pathogenesis will be discussed.

Autore Pugliese

• Navarro Ramirez Beatriz , Di Serio Francesco

Tutti gli autori

• Navarro B.; Gisel A.; Serra P.; Flores R.; Di Serio F.

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Anno di pubblicazione

2018

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