The Molecular Mechanism Of Promoting Function Divergence In Plant Acitn-Depolymerizing Factor(ADF) Gene Famliy Throughout Evolution

Functional divergence in paralogs is an important genetic source of evolutionary innovation.In organism,natural selection after genes duplicating will promote the daughter genes to experience three evolutional fate,pseudogenization,subfunctionalization and neofunctionalization.However,the mechanisms shaping the fate of duplicated genes remain heavily debated because the molecular processes and evolutionary forces involved are difficult to reconstruct.Thus,studying the functional divergence of gene families is important for elucidating the process of biological evolutionActin-depolymerizing factors(ADFs)are among the most important actin binding proteins and are involved in generating and remodeling actin cytoskeletal architecture via their conserved F-actin severing or depolymerizing activity.In plants,ADFs coevolved with actin,but their biochemical properties are diverse.Unfortunately,the biochemical function of most plant ADFs and the potential mechanisms of their functional divergence remain unclear.In this study,we perform an analysis for the 11 members of AtADF gene family using biochemistry and bioinformatics.The results show as below:(1)All 11 ADF genes in Arabidopsis thaliana exhibit opposing biochemical properties and their functions can be divided into two different types,D-type(depolymerizing F-actin)and B-type(bundling F-actin).(2)Arabidopsis thaliana subclass III ADFs,including AtADF5 and AtADF9,evolved F-actin bundling(B-type)function from conserved F-actin depolymerizing(D-type)function.(3)Arabidopsis thaliana subclass I ADFs,including AtADF1 to At ADF4,have enhanced D-type function.(4)By tracking historical mutation sites on ancestral proteins,several fundamentalamino acid residues affecting the biochemical functions of these proteins were identified in Arabidopsis and various plants,suggesting that the biochemical divergence of ADFs has been conserved during the evolution of angiosperm plants.(5)N-terminal extensions on subclass III ADFs that arose from intron-sliding events are indispensable for the alteration of D-type to B-type function.We conclude that the evolution of these N-terminal extensions and several conserved mutations produced the diverse biochemical functions of plant ADFs from a putative ancestor.In together,the findings of this study suggest that plant ADFs evolved F-actin bundling(B-type)function from conserved F-actin depolymerizing(D-type)function and show how the opposing and diverse biochemical properties of plant ADFs were acquired via key amino acid changes throughout evolution.