Important processes during differentiation and early development of somatic embryos of Norway spruce as revealed by changes in global gene expression

Daniel Vestman,Emma Larsson,John Cairney,Sara Von Arnold,Daniel Uddenberg,Eva Sundberg,David Clapham

doi:10.1186/1753-6561-5-s7-p78

Daniel Vestman, Emma Larsson + Show 5 more

Open Access

https://doi.org/10.1186/1753-6561-5-s7-p78

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Journal: BMC Proceedings	Publication Date: Sep 13, 2011
Citations: 60	License type: CC BY 2.0

Affiliation: Swedish University of Agricultural Sciences

Abstract

The aim of this study has been to identify important processes that regulate early stages of embryo development in conifers. Somatic embryogenesis in Picea abies has become a model system for studying embryology in conifers, providing a well-characterized sequence of developmental stages, resembling zygotic embryogeny, which can be synchronized by specific treatments, making it possible to collect a large number of somatic embryos at specific developmental stages. We have used this model to analyze global changes in gene expression during early stages of embryo development by generating an expression profile of 12,536 complementary DNA clones. This has allowed us to identify molecular events regulating putative processes associated with pattern formation during the earliest stages of embryogenesis which have not been identified on the molecular level in conifers before. We recognize notable changes in the expression of genes involved in regulating auxin biosynthesis and auxin response, gibberellin-mediated signaling, signaling between the embryo and the female gametophyte, tissue specification including the formation of boundary regions, and the switch from embryonic to vegetative development. In addition, our results confirm the involvement of previously described processes, including stress, differentiation of a protoderm, and programmed cell death.

Highlights

Most morphogenic events in plants occur in the sporophyte following seed germination, the embryonic phase is crucial as it is that the meristems are specified and the shoot-root body pattern of the plant is established
We have focused on the first stages of embryogenesis: the differentiation of early embryos from proembryogenic masses (PEMs) and the beginning of the development of late embryos
The relative abundances of Gene Ontology (GO) terms within the sets of differentially expressed genes were compared against the GO distribution of all clones on the array.We observed a general over-representation of genes involved in response to stress, both during the transition from proliferation to differentiation of early embryos and from differentiation of early to development of late embryos

Summary

Introduction

Most morphogenic events in plants occur in the sporophyte following seed germination, the embryonic phase is crucial as it is that the meristems are specified and the shoot-root body pattern of the plant is established. We are using somatic embryogenesis in Norway spruce (Picea abies) as a model system for studying embryology in conifers. We have extended the study of early events during embryogenesis in Norway spruce, by using microarray slides spotted with 12,536 cDNA clones from loblolly pine cDNA libraries. We have focused on the first stages of embryogenesis: the differentiation of early embryos from proembryogenic masses (PEMs) and the beginning of the development of late embryos. Few such studies have been undertaken and the work, which we describe here, is the first comprehensive analysis of gene expression of a conifer species during early stages of somatic embryogenesis.

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