Nonprotein-Coding RNAs as Regulators of Development in Tunicates

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genomics

Background:

• Tunicates (urochordates) are vital sister group to vertebrates, offering insights into chordate evolution.
• Tunicate genomes exhibit rapid evolution, including reduction, rearrangements, and loss of conserved elements.
• Noncoding RNAs (ncRNAs), especially microRNAs (miRNAs), are key regulators of animal development and morphological complexity.

Purpose of the Study:

• To review the discovery, evolution, and genome organization of the tunicate miRNA repertoire.
• To highlight the drastic reduction and restructuring of miRNAs in tunicates compared to chordate ancestors.
• To discuss known functions of miRNAs in tunicate development, muscle development, and regeneration.

Main Methods:

• Comparative genomics analysis of tunicate genomes.
• Focus on microRNA (miRNA) repertoire and other noncoding RNAs (ncRNAs).
• Review of existing literature on tunicate developmental biology and ncRNA functions.

Main Results:

• Tunicate genomes have undergone significant reduction and restructuring, particularly in their miRNA complement.
• The tunicate miRNA repertoire is drastically reduced compared to the chordate ancestor.
• Specific miRNAs regulate key developmental processes, including muscle development and oral siphon regeneration.

Conclusions:

• The reduced and reorganized miRNA repertoire in tunicates reflects their rapid genome evolution.
• Understanding tunicate ncRNAs, especially miRNAs, is crucial for deciphering chordate evolution and developmental mechanisms.
• Further research into diverse ncRNAs like yellow crescent RNA, moRNAs, RMST lncRNAs, and SL RNAs is needed for a comprehensive view of tunicate development.