Potato Spindle Tuber Viroid Modulates Its Replication through a Direct Interaction with a Splicing Regulator.

Area of Science:

• Plant virology
• RNA biology
• Molecular genetics

Background:

• Viroids are small, circular, noncoding RNAs that infect plants and rely on RNA structure for function.
• Nuclear-replicating viroids, such as PSTVd, require a specific spliced form of transcription factor IIIA (TFIIIA-7ZF) for replication.
• Long noncoding RNAs (lncRNAs) and viroids share reliance on RNA structure for interactions with cellular factors.

Purpose of the Study:

• To investigate the interaction between PSTVd and the TFIIIA splicing regulator, ribosomal protein L5 (RPL5).
• To elucidate how PSTVd infection affects RPL5-mediated splicing of TFIIIA transcripts.
• To determine the role of RPL5 in PSTVd replication and TFIIIA-7ZF expression.

Main Methods:

• In vitro and in vivo interaction assays between PSTVd and RPL5.
• Analysis of TFIIIA splicing patterns in PSTVd-infected plants.
• Ectopic expression of RPL5 to assess its effect on TFIIIA-7ZF levels and PSTVd accumulation.
• Mapping the RPL5 binding site on the PSTVd genome.

Main Results:

• PSTVd directly interacts with RPL5 both in vitro and in vivo.
• PSTVd infection disrupts RPL5's regulatory role in TFIIIA splicing.
• Ectopic RPL5 expression reduces TFIIIA-7ZF levels and PSTVd accumulation.
• The RPL5 binding site is located in the central conserved region of PSTVd.

Conclusions:

• Viroids can modulate host splicing factors to regulate their own replication.
• PSTVd utilizes RPL5 to promote TFIIIA-7ZF expression, enhancing viroid propagation.
• RPL5 acts as a novel negative regulator of viroid replication in the nucleus.
• This study offers insights into noncoding RNA function, host-pathogen interactions, and potential viroid control strategies.