Plant virus satellites A single-stranded circular RNA that is encapsidated by a helper plant virus's larger RNA is correctly termed what?

Introduction / Context:
Plant pathogens include classical viruses, subviral agents, and satellite nucleic acids. Distinguishing viroids from virusoids is a frequent exam point in plant virology.

Given Data / Assumptions:

• Entity is single-stranded circular RNA (ss circRNA).
• It is encapsidated with a helper virus and depends on it for replication/packaging.
• It is described in the context of plant viruses.

Concept / Approach:
Viroids are autonomous, naked circular RNAs that do not encode proteins and do not require a helper virus coat for encapsidation. Virusoids are similar small circular RNAs but require a helper virus to supply capsid proteins and functions; they are encapsidated by that virus.

Step-by-Step Solution:

Verification / Alternative check:
Plant pathology texts classify satellite RNAs/virusoids as encapsidated by helper virus coat proteins, unlike viroids which are naked RNAs.

Why Other Options Are Wrong:

• Virion: a complete infectious virus particle, not a subviral RNA on its own.
• Viroid: circular RNA without encapsidation by helper virus.
• Satellite DNA: DNA-based, not RNA.
• Prion: misfolded protein agent, not nucleic acid.

Common Pitfalls:
Confusing viroids and virusoids because both are small circular RNAs; dependency on a helper virus is the key distinction.

Final Answer:
Virusoid