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An adaptive epigenetic memory in conifers with important implications for seed production

Published online by Cambridge University Press:  24 January 2012

Igor Yakovlev ,
Carl Gunnar Fossdal ,
Tore Skrøppa ,
Jorunn E. Olsen ,
Anne Hope Jahren  and
Øystein Johnsen
Igor Yakovlev*
Affiliation:
Norwegian Forest and Landscape Institute, PO Box 115, N-1431, Ås, Norway
Carl Gunnar Fossdal
Affiliation:
Norwegian Forest and Landscape Institute, PO Box 115, N-1431, Ås, Norway
Tore Skrøppa
Affiliation:
Norwegian Forest and Landscape Institute, PO Box 115, N-1431, Ås, Norway
Jorunn E. Olsen
Affiliation:
Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, N-1432, Ås, Norway
Anne Hope Jahren
Affiliation:
School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822, USA
Øystein Johnsen
Affiliation:
Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, N-1432, Ås, Norway
*
*Correspondence Email: igor.yakovlev@skogoglandskap.no
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Abstract

Conifers are evolutionarily more ancient than their angiosperm counterparts, and thus some adaptive mechanisms and features influenced by epigenetic mechanisms appear more highly displayed in these woody gymnosperms. Conifers such as Norway spruce have very long generation times and long life spans, as well as large genome sizes. This seemingly excessive amount of genomic DNA without apparent duplications could be a rich source of sites for epigenetic regulation and modifications. In Norway spruce, an important adaptive mechanism has been identified, called epigenetic memory. This affects the growth cycle of these trees living in environments with mild summers and cold winters, allowing them to adapt rapidly to new and/or changing environments. The temperature during post-meiotic megagametogenesis and seed maturation epigenetically shifts the growth cycle programme of the embryos. This results in significant and long-lasting phenotypic change in the progeny, such as advance or delay of vital phenological processes of high adaptive value, like bud break and bud set. This phenomenon is not only of important evolutionary significance but has clear practical implications for forest seed production and conservation of forest genetic resources. The underlying molecular mechanism that causes the ‘memory’ in long-lived woody species is currently under investigation. Here we summarize the information related to epigenetic memory regulation in gymnosperms, with special emphasis on conifers. The molecular mechanism behind this is still unknown but transcriptional changes are clearly involved. Epigenetic regulation may be realized through several mechanisms, including DNA methylation, histone modification, chromatin remodelling, small non-coding RNAs and transposable element regulation, of which non-coding RNAs might be one of the most important determinants.

Keywords

adaptationchromatin remodellingconifersDNA methylationepigeneticsgenome sizehistone modificationsmegagametogenesissmall RNAstransposable element
Type
Review Papers
Information
Seed Science Research , Volume 22 , Issue 2 , June 2012 , pp. 63 - 76
Copyright
Copyright © Cambridge University Press 2012

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