Bias and evolution of the mutationally accessible phenotypic space in a developmental system

Area of Science:

• Evolutionary biology
• Developmental biology
• Genetics

Background:

• Genetic and developmental factors can bias the introduction of new variations.
• Understanding these biases is crucial for characterizing evolutionary trajectories.
• Quantitative data on mutationally inducible phenotypic variation and its causes are lacking.

Purpose of the Study:

• To quantify the mutationally accessible phenotypic spectrum of the vulval developmental system.
• To investigate genotype-dependence and underlying molecular/developmental causes of these biases.
• To identify mutationally sensitive elements that may indicate potential evolutionary variation.

Main Methods:

• Utilized mutation accumulation (MA) lines from four wild isolates of Caenorhabditis elegans and C. briggsae.
• Quantified developmental precision and variants in MA lines.
• Analyzed genotype-specific biases in phenotypic variation.

Main Results:

• Spontaneous mutations generally decrease developmental precision, with MA lines showing increased defects.
• A strong developmental bias exists, with certain variants being commonly induced while others are rare.
• Both the extent and spectrum of variation are genotype-dependent, with C. briggsae showing a two-fold greater decline in precision than C. elegans.
• Specific variant generation is influenced by genetic background, likely due to cryptic variation in molecular cascades.

Conclusions:

• Developmental systems and genotypes significantly bias the spectrum of mutationally inducible phenotypic variants.
• Cryptic genetic variation in molecular cascades underlies genotype-specific developmental biases.
• Evolutionary trends in the vulval system align with phenotypic characters most susceptible to mutation, suggesting developmental bias influences evolutionary directions.