Expression Analyses of Embryogenesis-Associated Genes during Somatic Embryogenesis of Adiantum capillus-veneris L. In vitro: New Insights into the Evolution of Reproductive Organs in Land Plants

Abstract

An efficient in vitro regeneration system via somatic embryogenesis (SE) was developed for a fern species Adiantum capillus-veneris. Adventitious shoots, green globular bodies (GGBs) and calli were obtained with the maximal induction rate on the Murashige and Skoog (MS) medium of low concentrations of 6-benzyladenine (BA) (0–1.0 mg/L), 2.0 mg/L BA without 2,4-dichlorophenoxyacetic acid (2,4-D), 0.5 mg/L 2,4-D and 0.5–1.0 mg/L 6-BA, respectively. Cyto-morphological and histological changes in the shoot development via calli and GGBs were examined. For a better understanding of these developmental events, expression patterns of six genes, AcLBD16, AcAGL, AcBBM, AcWUS, AcRKD, and AcLEC1, were characterized during SE. AcBBM and AcLEC1 were ubiquitously expressed in direct SE (adventitious shoots and GGBs) the maximal expression of AcBBM in mature GGBs, and the high expression of AcLEC1 in GGB initiation and adventitious shoots. During the indirect SE, AcLBD16, AcLEC1, AcRKD, and AcWUS were highly expressed in mature calli. Additionally, phylogenetic analyses showed that AcWUS, AcBBM, AcLBD, AcAGL, AcRKD, and their homologs of other green plants formed monophyletic clades, respectively. Some of these gene families, however, diversified rapidly with the occurrence of embryophytes, suggesting that embryogenesis-associated genes could experience a rapid evolution with the colonization of plants to terrestrial environments. Expression and phylogenetic analyses of those embryogenesis-associated genes by the aid of in vitro regeneration system of A. capillus-veneris provide new insights into the evolution of reproductive organs in land plants.

Somatic Embryogenesis Induction in Woody Species: The Future After OMICs Data Assessment

“…(2008), in A. thaliana , SERK expression precedes and coincides with early embryogenesis and again these authors considered AtSERK1 as a marker of competence for embryogenesis. Different authors have recognized SERK1 as a positive regulator of somatic embryogenesis in dicots (De Oliveira Santos et al., 2005; Ma et al., 2012; Zhai et al., 2015), monocots (Hu et al., 2005), and conifers (Li et al., 2014; Rupps et al., 2016 and Li et al., 2017a,b). Magnani et al.…”

“…Recently, Li et al. (2017a,b) demonstrate the over-expression of SERK-like genes following biotic and abiotic stresses. It is worthwhile to assume that the stress conditions imposed on the explants for SE induction may activate SERK genes coding for transmembrane SERK proteins capable of signal perception and transduction, giving rise to a cascade of events responsible for change of cell fate from competent cells.…”

Sugar Treatments Can Induce AcLEAFY COTYLEDON1 Expression and Trigger the Accumulation of Storage Products during Prothallus Development of Adiantum capillus-veneris

“…Parallel to the above mentioned gene sequence and function analysis, Li et al (2013) have developed A. capillus-veneris as an experimental system. They not only systematically described the morphological process of this plant ( Li et al, 2013 ), but established a culture system for shoot regeneration ( Li et al, 2017 ). In the assay of gene expression during shoot regeneration from sporophyte tissue, they found that expression of AcLEC1 was not only induced by stresses such as drought and ABA ( Xie et al, 2008 ), but also by cultural conditions ( Li et al, 2017 ).…”

“…They not only systematically described the morphological process of this plant ( Li et al, 2013 ), but established a culture system for shoot regeneration ( Li et al, 2017 ). In the assay of gene expression during shoot regeneration from sporophyte tissue, they found that expression of AcLEC1 was not only induced by stresses such as drought and ABA ( Xie et al, 2008 ), but also by cultural conditions ( Li et al, 2017 ). These observations sparked a modified hypothesis about the relationship between the origin of the seed maturation process and the LEC1 gene: LEC1-type HAP3 genes may origin for other functions, as it was induced upon stresses.…”

“…Unfortunately, gene transformation system of A. capillus-veneris has not yet been established. However, the induction of AcLEC1 expression during tissue culture of sporophyte ( Li et al, 2017 ) suggests that other approach can be used to test the hypothesis. While the prothalli cannot tolerant drought or ABA treatment, sugar might be the best candidate as an inducer of AcLEC1 expression.…”