W chromosome expression responds to female-specific selection.

Area of Science:

• Evolutionary genetics
• Genomics
• Animal breeding

Background:

• The W chromosome, inherited only by females, is expected to be shaped by female-specific selection.
• Nonrecombining genomic regions face degradative forces, making the W chromosome's evolutionary trajectory unclear.
• Understanding selection's role is crucial for W chromosome evolution and female fitness.

Purpose of the Study:

• To investigate the impact of female-specific selection on W chromosome gene expression.
• To identify W-linked genes and assess their expression patterns under varying selection pressures.
• To determine if positive selection preserves the W chromosome from decay.

Main Methods:

• Expanded the catalog of known W-linked genes in chickens.
• Analyzed W chromosome gene expression across different chicken breeds and the Red Jungle Fowl.
• Compared gene expression after over 100 generations of distinct female-specific selection regimens.

Main Results:

• Female-specific selection significantly altered W chromosome gene expression patterns.
• A convergent pattern of gene up-regulation was observed with increased female-specific selection.
• Transcriptional changes in selected breeds resulted from positive selection, indicating its role in W chromosome evolution.

Conclusions:

• Female-specific selection is a potent force shaping gene expression on the W chromosome.
• Positive selection acts to preserve the W chromosome, counteracting degradative forces.
• The W chromosome plays a vital role in female fertility and fitness in female heterogametic species.