PRC2 Represses Hormone-Induced Somatic Embryogenesis in Vegetative Tissue of Arabidopsis thaliana.

Iva Mozgová,Lars Hennig,Rafael Muñoz-Viana,Ortrun Mittelsten Scheid

doi:10.1371/journal.pgen.1006562

Abstract

Many plant cells can be reprogrammed into a pluripotent state that allows ectopic organ development. Inducing totipotent states to stimulate somatic embryo (SE) development is, however, challenging due to insufficient understanding of molecular barriers that prevent somatic cell dedifferentiation. Here we show that Polycomb repressive complex 2 (PRC2)-activity imposes a barrier to hormone-mediated transcriptional reprogramming towards somatic embryogenesis in vegetative tissue of Arabidopsis thaliana. We identify factors that enable SE development in PRC2-depleted shoot and root tissue and demonstrate that the establishment of embryogenic potential is marked by ectopic co-activation of crucial developmental regulators that specify shoot, root and embryo identity. Using inducible activation of PRC2 in PRC2-depleted cells, we demonstrate that transient reduction of PRC2 activity is sufficient for SE formation. We suggest that modulation of PRC2 activity in plant vegetative tissue combined with targeted activation of developmental pathways will open possibilities for novel approaches to cell reprogramming.

Highlights

Plant cells have long been recognized for their capacity to become pluripotent and to enter various differentiation pathways in response to chemical or mechanical stimuli
The potential of Arabidopsis zygotic embryos for auxin-induced somatic embryogenesis is lost during germination In Arabidopsis, external application of the synthetic auxin 2,4-D to immature ZEs induces reprogramming and development of SEs [4,5,6,7, 16]
While exposure to 2,4-D for 3 or 5 days resulted in the emergence of trichome-bearing true leaves from the shoot-apical meristem (SAM) region of the ZE (Fig 1C), an exposure for 7 days resulted in the formation of callus-like tissue in the SAM region (Fig 1B) from which primary SEs emerged in 60–70% of ZEs (Fig 1D–1F)

Summary

Introduction

Plant cells have long been recognized for their capacity to become pluripotent and to enter various differentiation pathways in response to chemical or mechanical stimuli This is exemplified by ectopic organ formation and entire plant regeneration from vegetative tissue in response to plant hormone and/or stress signaling, which is widely used for clonal propagation of horticultural species and as a developmental model system [1, 2]. Hormone-mediated SE induction requires sexual reproduction, as a high potential for SE formation is limited to microspores or zygotic embryos (ZEs) [16,17,18,19] This applies to Arabidopsis where ZEs present the most efficient source of auxin-induced SEs [16, 17]. Molecular barriers that prevent somatic embryogenesis from vegetative tissue remain poorly understood

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Results

Conclusion