Menzerath-Altmann's Law of Syntax in RNA Accretion History.

Fengjie Sun,Gustavo Caetano-Anollés

doi:10.3390/life11060489

Abstract

RNA evolves by adding substructural parts to growing molecules. Molecular accretion history can be dissected with phylogenetic methods that exploit structural and functional evidence. Here, we explore the statistical behaviors of lengths of double-stranded and single-stranded segments of growing tRNA, 5S rRNA, RNase P RNA, and rRNA molecules. The reconstruction of character state changes along branches of phylogenetic trees of molecules and trees of substructures revealed strong pushes towards an economy of scale. In addition, statistically significant negative correlations and strong associations between the average lengths of helical double-stranded stems and their time of origin (age) were identified with the Pearson’s correlation and Spearman’s rho methods. The ages of substructures were derived directly from published rooted trees of substructures. A similar negative correlation was detected in unpaired segments of rRNA but not for the other molecules studied. These results suggest a principle of diminishing returns in RNA accretion history. We show this principle follows a tendency of substructural parts to decrease their size when molecular systems enlarge that follows the Menzerath–Altmann’s law of language in full generality and without interference from the details of molecular growth.

Highlights

Accretion brings together disparate parts to form bigger wholes in a process of growth and innovation that is likely universal [1]
The first use of structural information to reconstruct the history of RNA accretion began as either ancestral character state reconstructions (CSRs) along branches of a tree of life generated from rRNA [8] or directly as trees of molecular substructures describing their gradual addition to growing ribosomal molecules [9]
We show ancestral CSRs and phylogenetic mappings of lengths in tRNA, 5S rRNA, RNase P RNA, and rRNA reveal the existence of a principle of diminishing returns in RNA accretion history that resembles that found in proteins

Summary

Introduction

Accretion brings together disparate parts to form bigger wholes in a process of growth and innovation that is likely universal [1]. The first use of structural information to reconstruct the history of RNA accretion began as either ancestral character state reconstructions (CSRs) along branches of a tree of life generated from rRNA [8] or directly as trees of molecular substructures describing their gradual addition to growing ribosomal molecules [9]. These novel approaches that embed “structure and function directly into phylogenetic analysis” point the way to “how structures evolve from one to the other” [10]. The approach unfolded the translocation (‘turnstile’) origin and co-evolving history of the RNA and proteins that make up the entire ribosomal complex, the machinery responsible for protein biosynthesis [21]

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Results

Conclusion