Ordered origin of the typical two- and three-repeat Myb genes.

Area of Science:

• Evolutionary biology
• Molecular genetics
• Bioinformatics

Background:

• Myb domain proteins feature conserved DNA-binding domains with 1-4 repeat motifs.
• Animal Myb proteins typically have three repeats (R1R2R3), while plants possess a large, diverse family with common R2R3 motifs.
• Myb protein sequences show high variability outside the conserved DNA-binding domain.

Purpose of the Study:

• To investigate the evolutionary origins and diversification of Myb genes.
• To analyze the evolutionary patterns of individual Myb repeats (R1, R2, R3).
• To propose a refined model for the evolution of the Myb gene family.

Main Methods:

• Cloning and sequencing of Myb domains from maize and sorghum.
• Comprehensive phylogenetic analysis of Myb genes.
• Comparative analysis of Myb repeat evolutionary rates.

Main Results:

• Individual Myb repeats exhibit distinct evolutionary origins, with R2 evolving slower than R1 and R3.
• R2R3 and R1R2R3 Myb genes likely co-existed in eukaryotes prior to plant-animal divergence.
• A model proposing R1R2R3 Myb genes evolved from R2R3 ancestors via R1 repeat gain is supported.
• Non-typical Myb proteins show polyphyletic origins, and ancient Myb paralogs predating current gene amplification were identified.

Conclusions:

• The Myb gene family evolved in an ordered manner, with a proposed gain of the R1 repeat.
• This study provides a more parsimonious explanation for Myb gene evolution compared to previous models.
• A new model for the ordered evolution of the Myb gene family is presented, integrating findings on repeat origins and diversification.