The differentially expressed proteins during somatic embryog
The differentially expressed proteins during somatic embryogenesis are described as the proteins that are induced by oxidative stress and respond to higher cell division activity including ascorbate peroxidase, dehydroascorbate reductase, glutathione transferase and mitochondrial manganese superoxide dismutase (Takáč et al., 2011). In addition, Silva et al. (2014) revealed the identification of expressed proteins during acquisition of oil palm embryogenenic callus formation. Some proteins can be developed into biomarkers such as typeIIIa membrane protein cp-wap13, fructokinase and PR proteins. Furthermore, the classification of perspective proteomics represents a majority of protein function that is involved in metabolism and serves as an alternative energy source, and the synthesis of primary metabolites for somatic embryo development in secondary somatic embryogenesis in cassava (Manihot esculenta) (Baba et al., 2008) as well as in Quercus suber (Gomez-Garay et al., 2013). However, the understanding of protein post-translational modification is still unclear Protein glycosylation is one of the most common processes that occur in the post-translational modification and approximately 50% of cellular protein is glycosylated (VandenSteen et al., 1998). There are two types of protein glycosylation pathway: N and O-glycosylation. The N-glycosylation in plants is found in the consensus sequence of Ans-x-Ser/Thr (X≠ proline). This type of glycosylation is generally the attachment of various preassembled monosaccharide precursors in the lumen of the endoplasmic reticulum (ER) to asparagine residues. On the other hand, O-glycosylation varies among plant species, and the monosaccharide precursors are normally attached to serine residues from the extensins (EXTs) as well as other members of the hydroxyproline-rich glycoprotein (Hyp) family with a single derivative galactose (Saito et al., 2014; Strasser, 2016; Schoberer and Strasser, 2017). N-glycan and O-glycan of protein primarily occur in the secretory system (ER and Golgi) and can result in functional protein changes which are influenced by subcellular localization (Oxley et al., 2004; Zhou et al., 2005). Moreover, N-/O- glycoproteins are believed to play a vital role in protein stability, protein activity and protein function to control many aspects such as signaling for regulation of plant growth, cell polarity, morphogenesis and daunorubicin sale to biotic and abiotic stress (Baluška et al., 2003; Šamaj et al., 2003; Cannesan et al., 2012; Nguema-Ona et al., 2014). In previous study, glycoprotein was responsible for the inhibition and regulation of cell polarity in Ustilago scitaminea teliospores inoculated in sugarcane (Millanes et al., 2005). Xu et al. (2011) characterized hydroxyproline-rich glycoprotein during somatic embryogenesis of banana (Musa spp. AAA) using immunofluorescence labelling. The result suggested that this glycoprotein plays an important role especially in the process of embryo germination during plant regeneration via somatic embryogenesis of banana somatic embryos. However, profound insight into glycoproteomics during somatic embryogenesis is still lacking. The current study aimed to identify N-glycoproteomics, which may have important roles in response to somatic embryogenesis in oil palm tissue culture.
Materials and methods
Conflicts of interest
Acknowledgements This research was supported by the Kasetsart University Research and Development Institute and a graduate scholarship was provided by the National Research Council of Thailand in the 2017 fiscal year. The Proteomic Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), Pathum Thani, Thailand provided shotgun proteomics analysis.
Introduction Histidine-rich glycoprotein (HRG) is one of many plasma glycoproteins that are predominantly generated in the liver and are also called histidine-proline-rich glycoproteins (HPRGs) . As the name indicates, HRG possesses a notable number of histidine residues consisting 12.6% of total amino acid of human HRG and 11% of mouse HRG. Several kinds of molecules have been observed to interact with HRG, such as heparin, heparan sulfate, fibrin, fibrinogen, thrombospondin, divalent metal cations, and complement C1q , , , , . In addition, in vivo studies using Hrg mice (Hrg knockout, gene-manipulated mice) have shown shorter prothrombin time and higher fibrinolytic activity than wild-type mice, and these mice were susceptible to Candida albicans , . These results demonstrate both anticoagulant and antifibrinolytic properties, as well as antifungal and antibacterial activities of HRG , . Thus, HRG, which is an abundant plasma component, is thought to be one of the critical adaptor proteins involving in immune responses, coagulation, and fibrinolysis. However, less information on equine HRG has been provided until today, except for the predicted gene sequence of equine HRG in the National Center for Biotechnology Information database.