Germin-like genes are expressed during somatic embryogenesis and early development of conifers

Abstract

Germins and germin-like proteins (GLPs) are members of a superfamily of proteins widely distributed in plants. Their localization within the extracellular matrix and in some cases their hydrogen peroxide-producing activity suggests that these proteins are involved in cell wall metabolism during stress responses and developmental processes. Several very highly conserved conifer GLPs have been identified in somatic embryo tissues. In order to gain more knowledge on their potential involvement in the development of this particular tissue, we have characterized a new GLP gene, LmGER1 in hybrid larch. Anti-GLP immunserum and in-gel activity analyses suggested the presence of superoxide dismutase activity in apoplastic proteins from larch somatic embryos. These results could indicate a possible role for LmGER1 in this physiological process. The expression of LmGER1 has been followed during the maturation of somatic embryos and in different organs of young plantlets by homologous transformation with a promoter-gus construct. This promoter was activated in the root cap of young embryos and, later on, in the cotyledons and in the vascular procambium and xylem. Furthermore, the importance of this gene in embryo development was evaluated by transforming embryonal masses with a gene construct encoding a hairpin RNA leading to gene silencing. The potential role of LmGER1 in cross-linking of cell wall components is discussed.

De novo assembly and characterization of global transcriptome of coconut palm (Cocos nucifera L.) embryogenic calli using Illumina paired-end sequencing

“…The role of GLPs in enhancing somatic embryogenesis has been reported in Pinus caribaea (Domon et al 1995) and Pinus radiata (Bishop-Hurley et al 2003). Mathieu et al (2006) has reported that a GLP played a key role in somatic embryo formation in hybrid larch possibly through regulation of cell wall remodeling, which was essential for correct embryo development. Expression of ECPs have been reported to be regulated by ABA-inducible genes during acquisition of embryogenic competence (Kiyosue et al 1992).…”

Versatility of germin-like proteins in their sequences, expressions, and functions

“…Transcript study revealed that PcGER1 was abundant in all the embryonic lines but absent from the nonembryogenic lines whereas the PcGER1 specific transcript was detected in the quiescent zygotic embryos but not detectable in the female gametophyte and the haploid storage tissue (Neutelings et al 1998). Similarly, a small number of GLPs were found to have high transcript level expression in embryogenic tissues but no expression in nonembryogenic tissues such as roots, shoots, needles, and callus tissue in Pinus radiata (Bishop-Hurley et al 2003) and in other conifers (Mathieu et al 2006). A very recent study on Pinus pinaster identified germin-like protein and ubiquitin-protein ligase as a probable marker for somatic embryogenesis cultured on high gellan gum concentration (Morel et al 2014).…”

Recent progress in the understanding of tissue culture-induced genome level changes in plants and potential applications

“…Biochemical activity of cell wall enzymes such as b-1,3-glucanases in chicory (Helleboid et al 1998;2000), cell wall and membrane associated proteoglycan proteins such as glucosamine-and acetylated glucosamine-containing arabinogalactan proteins in carrot (van Hengel et al 2001), abscisic acid (ABA) inducible expression of embryo-specific globulin protein in maize (Duncan et al 2003), and germin-like proteins in conifer cultures (Mathieu et al 2006) are found to be associated with somatic embryo induction. Recently, a mutant Arabidopsis was identified with an inability to regenerate shoots in in vitro culture, attributed to a defect in fasciclin-like arabinogalactan protein expression (Johnson et al 2011).…”