Extension of the Unit Root Test: The Fractional Augmented Dickey-Fuller Test A Monte Carlo Study

ABSTRACT Usually we use the Dickey-Fuller test for testing stationarity in a time series under the hypotheses H 0 : I (1) (presence of unit root) versus H 1 : I (0) (absence of unit root), and it is used in the case of a short memory. In this article, we propose an extension of the fractional Dickey-Fuller test proposed by Bensalma used in the long memory case and when the errors of test regression are autocorrelated. The proposed test is considered as a generalization of ADF test and they have the same steps. The asymptotic properties of this test are derived and it is studied by Monte Carlo simulation experiment. The paper ends with an application to illustrate the usefulness and the simplicity of the proposed technique

Seed dormancy breaking of an endangered medicinal tree species (Taxus baccata L.) using embryo culture

Natural regeneration of Taxus baccata L. is constrained due to the depth of seed dormancy requirements (often taking two or more years) and low seed germination. Further, the conventional method of vegetative propagation by cuttings is associated with difficulties in rooting. Hence, for the first time, this study describes an efficient and reproducible in vitro protocol for breaking the dormancy of seeds from the endangered forest tree T. baccata L. via zygotic embryo culture. Embryos isolated from 100% sterile seeds were cultured on DCR medium that contains sucrose (30 g/l), agar (8 g/l), and activated charcoal (5 g/l), fortified with different concentrations of Plant Growth Regulators (PGRs), and held at a temperature of 25 ± 2 ºC in a growth room. The results revealed that the in vitro embryo germination percentage was mostly affected by gibberellic acid (GA3) and thidiazuron (TDZ). Among the nine treatments, the treatments with 0.5 mg/l TDZ and 1 mg/l GA3 showed the highest germination (100%), while the other treatments all increased the germination percentages significantly compared to the control (37.5%). The 1/2 DCR medium with the addition of 0.1 mg/l indole-3-butyric acid (IBA) resulted in the highest rooting ratio (94%). However, the greatest root and hypocotyl elongation (59.37 ± 3.77 and 62.75 ± 4.43 mm, respectively) occurred when seedlings were cultured on 1/2 DCR medium containing 0.5 mg/l BA. Plantlets were transplanted into plastic pots containing an autoclaved garden soil, sand, and vermiculite mixture (1:1:1) and held at a temperature of 25 ± 2 ºC in a growth room for 4 weeks before being transplanted into the greenhouse. These results indicated that the protocol developed during the current study will be useful to overcome seed dormancy and for multiplication and conservation of the species T. baccata L

Recent advances on host plants and expression cassettes' structure

Plant molecular pharming is a promising system to produce important recombinant proteins such as therapeutic antibodies, pharmaceuticals, enzymes, growth factors, and vaccines. The system provides an interesting alternative method to the direct extraction of proteins from inappropriate source material while offering the possibility to overcome problems related to product safety and source availability. Multiple factors including plant hosts, genes of interest, expression vector cassettes, and extraction and purification techniques play important roles in the plant molecular pharming. Plant species, as a biosynthesis platform, are a crucial factor in achieving high yields of recombinant protein in plant. The choice of recombinant gene and its expression strategy is also of great importance in ensuring a high amount of the recombinant proteins. Many studies have been conducted to improve expression, accumulation, and purification of the recombinant protein from molecular pharming systems. Re-engineered vectors and expression cassettes are also pivotal tools in enhancing gene expression at the transcription and translation level, and increasing protein accumulation, stability, retention and targeting of specific organelles. In this review, we report recent advances and strategies of plant molecular pharming while focusing on the choice of plant hosts and the role of some molecular pharming elements and approaches: promoters, codon optimization, signal sequences, and peptides used for upstream design, purification and downstream processing

Synergistic effects of polyploidization and elicitation on biomass and hyoscyamine content in hairy roots of Datura stramonium

Description of the subject. The hyoscyamine, a tropane alkaloid, widely used in medicine, can be produced from Datura sp. (Solanaceae). However, its content in the spontaneous roots remains low; therefore, hairy roots (HRs) were envisaged as a potential alternative to improve its biosynthesis. The hairy roots are characterized by a good genetic stability and a rapid growth. Indeed, Datura stramonium HRs have widely been studied in the perspective of improving the yield of hyoscyamine. This study is part of this same perspective. Objectives. This paper aims to study the effects of polyploidization of HRs induced by colchicine in synergy with elicitation (with acetylsalicylic [ASA] or salicylic acids [SA]) on the hyoscyamine content in D. stramonium. Method. Colchicine was applied at different concentrations and periods, on a selected hairy root line (LDS) of D. stramonium obtained by infection with Agrobactrium rhizogenes strain A4. The selection of tetraploid HR lines was performed by the cytogenetic analysis using light microscopy. The effect of polyploidization and elicitation was studied on the biomass (dry weight) and hyoscyamine content of HRs. Results. The untreated HR line (control) shows a diploid level with 2n = 24 chromosomes. However, the HR lines treated with colchicine show, in most cases, an endoreduplication of their genetic material. The survival rate of endoreduplicated lines varies between 30% and 93%, depending on concentration and exposure time to colchicine. Moreover, the tetraploid HR line shows an increase in its biomass and hyoscyamine content in comparison to the diploid HR line (LDS). Further, elicitation of HRs by ASA or AS at the 10-4 M concentration causes a low decrease or increase in dry weight, respectively. However, the same treatments show a significant increase in the yield of hyoscyamine in elicited HR lines. Consequently, our work indicates that the combination of polyploidy and elicitation can lead to significant improvements in hyoscyamine biosynthesis and content due to their synergistic effects. Conclusions. Elicitation of tetraploid hairy root lines improves significantly their content of hyoscyamine

Engineering of Biomass Accumulation and Secondary Metabolite Production in Plant Cell and Tissue Cultures

Plants are the source of valuable secondary metabolites that are commonly used in pharmaceutical, food, agricultural, cosmetic, and textile industries. The increasing commercial importance of secondary metabolites has resulted in a great interest in research focusing on secondary metabolism and finding alternative ways for secondary metabolite production. Plant cell and tissue cultures are branches of plant biotechnology and they have been introduced as alternative ways for the production of valuable secondary metabolites. Plant technology provides a continuous and reliable source for pharmaceutical phytochemicals and can easily be scaled up. Therefore, plant cell and tissue cultures have a great potential to be used as an alternative to traditional agriculture for the industrial production of secondary metabolites. In this chapter, current techniques used for enhancing biomass accumulation and secondary metabolite production are discussed. © 2018 Elsevier Inc. All rights reserved