Length, orientation, and plant host influence the mutation frequency in microsatellites

Area of Science:

• Genetics
• Molecular Biology
• Plant Science

Background:

• Microsatellites are repetitive DNA sequences prone to length changes via polymerase slippage.
• Understanding factors influencing microsatellite mutation is crucial for plant genome stability studies.

Purpose of the Study:

• To investigate factors affecting spontaneous microsatellite mutation frequency in plants.
• To compare mutation rates across different microsatellite lengths and orientations.
• To assess inter-species variation in mutation rates between Arabidopsis and tomato.

Main Methods:

• Utilized a beta-glucuronidase (GUS) reporter system in Arabidopsis thaliana and tomato (Lycopersicon esculentum).
• Measured mutation frequencies in various microsatellite tracts (G(7), G(10), G(13), G(16), C(16)) in somatic tissues.
• Analyzed germinal transmission of mutations for highly mutable tracts.

Main Results:

• Mutation frequency significantly increased with microsatellite tract length (e.g., G(16) was ~80-fold more mutable than G(7)).
• Mutation frequency was influenced by repeat orientation (G(16) was 3-fold more mutable than C(16)).
• Arabidopsis thaliana showed a 5-fold higher mutation frequency than tomato for the same G(7) construct.

Conclusions:

• Microsatellite length and repeat orientation are key determinants of mutation frequency in plants.
• Significant inter-species differences in microsatellite mutation rates exist between Arabidopsis and tomato.
• Highly mutable microsatellites can lead to detectable germinal mutations, impacting heritability.