Axoneme specialization embedded in a "generalist" beta-tubulin

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• The C-terminal tail (CTT) of beta-tubulin is critical for axoneme structure and function.
• A conserved beta-tubulin axoneme motif in the proximal CTT was previously thought essential for 9+2 motile axoneme formation.
• The role of the distal CTT was considered less important for axoneme assembly.

Purpose of the Study:

• To investigate the precise relationship between the beta-tubulin CTT primary structure and axoneme assembly.
• To determine the essentiality of the beta-tubulin axoneme motif and the distal CTT for functional axoneme formation.
• To elucidate the specific roles of different CTT regions in Drosophila spermatogenesis.

Main Methods:

• Utilized Drosophila spermatogenesis-specific beta2-tubulin for structure-function studies.
• Generated and analyzed beta2-tubulin C-terminal truncations and sequence variants.
• Assessed the impact of CTT modifications on axoneme structure and sperm motility.

Main Results:

• Unexpectedly, some core sequence changes within the axoneme motif did not prevent motile axoneme formation.
• Deletion of the distal CTT did not impair functional sperm production, but specific sequence alterations in this region did.
• Both the proximal axoneme motif and the distal CTT are important for proper axoneme assembly and function.

Conclusions:

• The beta-tubulin CTT is more complex in its role in axoneme assembly than previously thought.
• The conserved axoneme motif likely facilitates central pair assembly, a sensitive axonemal structure.
• Beta2-tubulin possesses robust axoneme assembly properties, with specializations located in both the CTT and the molecular body.