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Role of the variable domain in modulating potato spindle tuber viroid replication
Y Hu1, P A Feldstein, P J Bottino
1Department of Plant Biology, University of Maryland, College Park 20742, USA.
Virology
|May 1, 1996
Summary
Researchers investigated mutations in Potato spindle tuber viroid (PSTVd) to find temperature-sensitive variants. While mutations altered replication and stability, no clear temperature-sensitive PSTVd mutants were identified, revealing complex evolutionary dynamics.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- Potato spindle tuber viroid (PSTVd) exhibits structural transitions crucial for its replication.
- The variable domain contains sequences vital for replication and "premelting regions" influencing structural stability.
- Premelting regions are key to understanding PSTVd's native structure breakdown in vitro.
Purpose of the Study:
- To investigate the structural and biological impacts of nucleotide substitutions in PSTVd's premelting region 3.
- To identify temperature-sensitive mutations affecting PSTVd replication and pathogenesis.
- To understand the relationship between structural stability, temperature, and PSTVd fitness.
Main Methods:
- Generated five single and two double nucleotide substitution mutants in PSTVd's premelting region 3.
- Assessed replication rates and analyzed progeny sequences for spontaneous changes.
- Evaluated the effect of higher temperatures on mutant replication and structural stability.
Main Results:
- None of the generated PSTVd mutants replicated as rapidly as the wild type.
- Spontaneous sequence changes were frequently observed in the progeny of the mutants.
- Increased temperatures partially alleviated replication inhibition caused by more stable structures, but no distinct temperature-sensitive mutants emerged.
- PSTVd populations demonstrated adaptability, shifting fitness peaks based on assay temperature and structural stability.
Conclusions:
- No well-defined temperature-sensitive PSTVd mutants were isolated through targeted nucleotide substitutions in premelting region 3.
- The interaction between assay temperature and in vivo structural stability exerts selective pressure on PSTVd populations.
- Selection can act on either the plus or minus strand of PSTVd, depending on mutation characteristics and location.