The Origin of the Cyathea delgadii Sternb. Somatic Embryos Is Determined by the Developmental State of Donor Tissue and Mutual Balance of Selected Metabolites.

Anna Mikuła,Wojciech Tomaszewicz,Michał Dziurka,Andrzej Kaźmierczak,Małgorzata Grzyb,Mirosław Sobczak,Jan Rybczyński,Piotr Zdańkowski

doi:10.3390/cells10061388

Abstract

Somatic embryogenesis is the formation of a plant embryo from a cell other than the product of gametic fusion. The need to recognize the determinants of somatic cell fate has prompted investigations on how endogenous factors of donor tissues can determine the pattern of somatic embryo origin. The undertaking of this study was enabled by the newly developed experimental system of somatic embryogenesis of the tree fern Cyathea delgadii Sternb., in which the embryos are produced in hormone-free medium. The contents of 89 endogenous compounds (such as sugars, auxins, cytokinins, gibberellins, stress-related hormones, phenolic acids, polyamines, and amino acids) and cytomorphological features were compared between two types of explants giving rise to somatic embryos of unicellular or multicellular origin. We found that a large content of maltose, 1-kestose, abscisic acid, biologically active gibberellins, and phenolic acids was characteristic for single-cell somatic embryo formation pattern. In contrast, high levels of starch, callose, kinetin riboside, arginine, and ethylene promoted their multicellular origin. Networks for visualization of the relations between studied compounds were constructed based on the data obtained from analyses of a Pearson correlation coefficient heatmap. Our findings present for the first time detailed features of donor tissue that can play an important role in the somatic-to-embryogenic transition and the somatic embryo origin.

Highlights

Examinations of the surface of C. delgadii stipe explants (STs) explants showed that their epidermis was composed of elongated cells, trichomes (Figure 1A), and stomata (Figure 1A,B)
Based on the semi-thin sections of STs, 3 anatomical regions were distinguishable: the epidermis, a cortex consisting of 5–6 layers of large parenchymatic cells, and a vascular cylinder (Figure 1C)
The pattern of the somatic embryo origin depends on the developmental status of the plant organ that has been used as an explant source, and is correlated with physiological state of donor tissues

Summary

Introduction

Every cell of living tissues can be used to establish an in vitro cell culture and the production of whole plants. Cells originating from different tissues and distinct parts of the plant body have different regenerative potential. In induced somatic embryogenesis (SE), which is the best example of totipotency expressed in a large number of plant species, the choice of explant is of fundamental importance for the pathway by which somatic embryos are produced (direct or indirect route) and their origin (unicellular or multicellular) [2]. The understanding of how the type of donor tissues impacts regenerative processes under tissue culture conditions is essential to work out approaches and protocols for improving the effectiveness of in vitro regeneration of plants

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