Comparative transcriptional profiling analysis of the two daughter cells from tobacco zygote reveals the transcriptome differences in the apical and basal cells.

Tian-Xiang Hu,Jie Zhao,Miao Yu

doi:10.1186/1471-2229-10-167

Abstract

BackgroundIn angiosperm, after the first asymmetric zygotic cell division, the apical and basal daughter cells follow distinct development pathways. Global transcriptome analysis of these two cells is essential in understanding their developmental differences. However, because of the difficulty to isolate the in vivo apical and basal cells of two-celled proembryo from ovule and ovary in higher plants, the transcriptome analysis of them hasn't been reported.ResultsIn this study, we developed a procedure for isolating the in vivo apical and basal cells of the two-celled proembryo from tobacco (Nicotiana tabacum), and then performed a comparative transcriptome analysis of the two cells by suppression subtractive hybridization (SSH) combined with macroarray screening. After sequencing, we identified 797 differentially expressed ESTs corresponding to 299 unigenes. Library sequence analysis successfully identified tobacco homologies of genes involved in embryogenesis and seed development. By quantitative real-time PCR, we validated the differential expression of 40 genes, with 6 transcripts of them specifically expressed in the apical or basal cell. Expression analysis also revealed some transcripts displayed cell specific activation in one of the daughter cells after zygote division. These differential expressions were further validated by in situ hybridization (ISH). Tissue expression pattern analysis also revealed some potential roles of these candidate genes in development.ConclusionsThe results show that some differential or specific transcripts in the apical and basal cells of two-celled proembryo were successfully isolated, and the identification of these transcripts reveals that these two daughter cells possess distinct transcriptional profiles after zygote division. Further functional work on these differentially or specifically expressed genes will promote the elucidation of molecular mechanism controlling early embryogenesis.

Highlights

In angiosperm, after the first asymmetric zygotic cell division, the apical and basal daughter cells follow distinct development pathways
In Arabidopsis, the mutations of gnom, root-shoot-hypocotyl-defective and yoda alter the asymmetric division of zygote, and result in the formation of two nearly equalsized daughter cells and subsequent defect of embryonic axis establishment [5,6,7]. It suggests that the asymmetric division of zygote producing the apical and basal cells is a crucial event of early embryogenesis
To avoid confusing the apical and basal cells from different proembryos, each proembryo was digested in an individual droplet of enzyme solution

Summary

Introduction

After the first asymmetric zygotic cell division, the apical and basal daughter cells follow distinct development pathways. The first zygotic cell division is transverse mutations of gnom (gn), root-shoot-hypocotyl-defective (rsh) and yoda (yda) alter the asymmetric division of zygote, and result in the formation of two nearly equalsized daughter cells and subsequent defect of embryonic axis establishment [5,6,7] It suggests that the asymmetric division of zygote producing the apical and basal cells is a crucial event of early embryogenesis. Embryo sac in higher plants is typically surrounded by the sporophytic tissues of ovule and ovary, access to the embryo is hampered To overcome these difficulties, the researchers utilize some in vitro culture systems to study the early embryo development mechanism [11,12,13,14,15]. Compared with embryogenesis in vivo, there are some differences in the way of embryos originate and develop, the results obtained in vitro fail to explain all the questions

Methods

Results

Discussion

Conclusion