Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.

<h4>Background</h4>It has been suggested that the chloroplast genomes of the grass family, Poaceae, have undergone an elevated evolutionary rate compared to most other angiosperms, yet the details of this phenomenon have remained obscure. To know how the rate change occurred during evolu...

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Autores principales:	Bojian Zhong, Takahiro Yonezawa, Yang Zhong, Masami Hasegawa
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2009
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/a4ea10a337864229a638c1acd453fe85
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spelling	oai:doaj.org-article:a4ea10a337864229a638c1acd453fe852021-11-25T06:23:02ZEpisodic evolution and adaptation of chloroplast genomes in ancestral grasses.1932-620310.1371/journal.pone.0005297https://doaj.org/article/a4ea10a337864229a638c1acd453fe852009-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/19390686/pdf/?tool=EBIhttps://doaj.org/toc/1932-6203<h4>Background</h4>It has been suggested that the chloroplast genomes of the grass family, Poaceae, have undergone an elevated evolutionary rate compared to most other angiosperms, yet the details of this phenomenon have remained obscure. To know how the rate change occurred during evolution, estimation of the time-scale with reliable calibrations is needed. The recent finding of 65 Ma grass phytoliths in Cretaceous dinosaur coprolites places the diversification of the grasses to the Cretaceous period, and provides a reliable calibration in studying the tempo and mode of grass chloroplast evolution.<h4>Methodology/principal findings</h4>By using chloroplast genome data from angiosperms and by taking account of new paleontological evidence, we now show that episodic rate acceleration both in terms of non-synonymous and synonymous substitutions occurred in the common ancestral branch of the core Poaceae (a group formed by rice, wheat, maize, and their allies) accompanied by adaptive evolution in several chloroplast proteins, while the rate reverted to the slow rate typical of most monocot species in the terminal branches.<h4>Conclusions/significance</h4>Our finding of episodic rate acceleration in the ancestral grasses accompanied by adaptive molecular evolution has a profound bearing on the evolution of grasses, which form a highly successful group of plants. The widely used model for estimating divergence times was based on the assumption of correlated rates between ancestral and descendant lineages. However, the assumption is proved to be inadequate in approximating the episodic rate acceleration in the ancestral grasses, and the assumption of independent rates is more appropriate. This finding has implications for studies of molecular evolutionary rates and time-scale of evolution in other groups of organisms.Bojian ZhongTakahiro YonezawaYang ZhongMasami HasegawaPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 4, Iss 4, p e5297 (2009)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Bojian Zhong Takahiro Yonezawa Yang Zhong Masami Hasegawa Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.
description	<h4>Background</h4>It has been suggested that the chloroplast genomes of the grass family, Poaceae, have undergone an elevated evolutionary rate compared to most other angiosperms, yet the details of this phenomenon have remained obscure. To know how the rate change occurred during evolution, estimation of the time-scale with reliable calibrations is needed. The recent finding of 65 Ma grass phytoliths in Cretaceous dinosaur coprolites places the diversification of the grasses to the Cretaceous period, and provides a reliable calibration in studying the tempo and mode of grass chloroplast evolution.<h4>Methodology/principal findings</h4>By using chloroplast genome data from angiosperms and by taking account of new paleontological evidence, we now show that episodic rate acceleration both in terms of non-synonymous and synonymous substitutions occurred in the common ancestral branch of the core Poaceae (a group formed by rice, wheat, maize, and their allies) accompanied by adaptive evolution in several chloroplast proteins, while the rate reverted to the slow rate typical of most monocot species in the terminal branches.<h4>Conclusions/significance</h4>Our finding of episodic rate acceleration in the ancestral grasses accompanied by adaptive molecular evolution has a profound bearing on the evolution of grasses, which form a highly successful group of plants. The widely used model for estimating divergence times was based on the assumption of correlated rates between ancestral and descendant lineages. However, the assumption is proved to be inadequate in approximating the episodic rate acceleration in the ancestral grasses, and the assumption of independent rates is more appropriate. This finding has implications for studies of molecular evolutionary rates and time-scale of evolution in other groups of organisms.
format	article
author	Bojian Zhong Takahiro Yonezawa Yang Zhong Masami Hasegawa
author_facet	Bojian Zhong Takahiro Yonezawa Yang Zhong Masami Hasegawa
author_sort	Bojian Zhong
title	Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.
title_short	Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.
title_full	Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.
title_fullStr	Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.
title_full_unstemmed	Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.
title_sort	episodic evolution and adaptation of chloroplast genomes in ancestral grasses.
publisher	Public Library of Science (PLoS)
publishDate	2009
url	https://doaj.org/article/a4ea10a337864229a638c1acd453fe85
work_keys_str_mv	AT bojianzhong episodicevolutionandadaptationofchloroplastgenomesinancestralgrasses AT takahiroyonezawa episodicevolutionandadaptationofchloroplastgenomesinancestralgrasses AT yangzhong episodicevolutionandadaptationofchloroplastgenomesinancestralgrasses AT masamihasegawa episodicevolutionandadaptationofchloroplastgenomesinancestralgrasses
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Episodic evolution and adaptation of chloroplast genomes in ancestral grasses.

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