WUSCHEL Overexpression Promotes Callogenesis and Somatic Embryogenesis in Medicago truncatula Gaertn.

Aline Kadri,Pascal Ratet,Ghislaine Grenier De March,François Guerineau,Viviane Cosson

doi:10.3390/plants10040715

Abstract

The induction of plant somatic embryogenesis is often a limiting step for plant multiplication and genetic manipulation in numerous crops. It depends on multiple signaling developmental processes involving phytohormones and the induction of specific genes. The WUSCHEL gene (WUS) is required for the production of plant embryogenic stem cells. To explore a different approach to induce somatic embryogenesis, we have investigated the effect of the heterologous Arabidopsis WUS gene overexpression under the control of the jasmonate responsive vsp1 promoter on the morphogenic responses of Medicago truncatula explants. WUS expression in leaf explants increased callogenesis and embryogenesis in the absence of growth regulators. Similarly, WUS expression enhanced the embryogenic potential of hairy root fragments. The WUS gene represents thus a promising tool to develop plant growth regulator-free regeneration systems or to improve regeneration and transformation efficiency in recalcitrant crops.

Highlights

Somatic embryogenesis is a promising approach and a powerful tool for the mass propagation of plants
The effect of WUSCHEL overexpression during regeneration via somatic embryogenesis was discernable when comparing WUS-expressing explants to control explants transformed with the pCambia-bar vector
The transgenic status of the plants selected by phosphinothricin was confirmed by polymerase chain reaction (PCR) amplification of the BAR and WUS sequences

Summary

Introduction

Somatic embryogenesis is a promising approach and a powerful tool for the mass propagation of plants. Explant cells can be induced to an embryogenic state by a variety of procedures that usually include exposition to exogenous stimuli like plant growth regulators, certain stress conditions (pH shock, low or high temperature, osmotic shock, drought) or treatments with various chemical substances [2,3]. In response to these signals, somatic cells acquire an embryogenic competence resulting from the action of a complex signaling network and from the reprogramming of gene expression patterns. Similar attempts have been reported in other species using BABY BOOM (BBM) in tobacco [13], pepper [14] cacao [15] and rice [16], LEC1 and LEC2 in tobacco [17], AGAMOUS-LIKE15 in soybean [18], BBM and WUS2 in maize [19]

Methods

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Discussion

Conclusion