Substrate Utilization by Suspension Cultures and Somatic Embryos of Daucus carota L. Measured by C NMR

Effectiveness of Humic Substances and Phenolic Compounds in Regulating Plant-Biological Functionality

Significant benefit of soil organic matter (SOM) to crop productivity is scientifically well documented. The main constituents and active fractions of SOM are humic substances (HS) and phenolic compounds. Since both these two components strongly impact plant–soil relationship, it is importantly from an ecological point of view to discriminate their biological effects and relating them to their composition. In this study we compared the biological effects of HS, and the soil water soluble phenols (SWSP) on growth, antioxidant activities, carbohydrates, proteins, phenols, and vitamins of Pinus laricio callus. Each extract was assessed for the content of low molecular weight organic acids, soluble carbohydrates, fatty acids, and phenolic acids. Moreover, Fourier transform infrared (FT-IR) and surface-enhanced Raman scattering (SERS) spectroscopies were applied to study their molecular structure. The results showed that HS produced better callus growth compared to the control and SWSP. Carbohydrates decreased in presence of HS while proteins, vitamin C and E increased. In contrast, in callus treated with SWSP the amount of glucose and fructose increased as well as all the antioxidant activities. The data evidenced that HS rich in tartaric and fatty acids had beneficial effects on callus growth contrary to soil water-soluble phenols rich in aldehydes, and syringic, ferulic, and benzoic acids.

ROS Homeostasis Regulates Somatic Embryogenesis via the Regulation of Auxin Signaling in Cotton

Somatic embryogenesis (S.E.) is a versatile model for understanding the mechanisms of plant embryogenesis and a useful tool for plant propagation. To decipher the intricate molecular program and potentially to control the parameters affecting the frequency of S.E., a proteomics approach based on two-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF/TOF was used. A total of 149 unique differentially expressed proteins (DEPs) were identified at different stages of cotton S.E. compared with the initial control (0 h explants). The expression profile and functional annotation of these DEPs revealed that S.E. activated stress-related proteins, including several reactive oxygen species (ROS)-scavenging enzymes. Proteins implicated in metabolic, developmental, and reproductive processes were also identified. Further experiments were performed to confirm the role of ROS-scavenging enzymes, suggesting the involvement of ROS homeostasis during S.E. in cotton. Suppressing the expression of specifically identified GhAPX proteins resulted in the inhibition of dedifferentiation. Accelerated redifferentiation was observed in the suppression lines of GhAPXs or GhGSTL3 in parallel with the alteration of endogenous ascorbate metabolism and accumulation of endogenous H₂O₂ content. Moreover, disrupting endogenous redox homeostasis through the application of high concentrations of DPI, H₂O₂, BSO, or GSH inhibited the dedifferentiation of cotton explants. Mild oxidation induced through BSO treatment facilitated the transition from embryogenic calluses (ECs) to somatic embryos. Meanwhile, auxin homeostasis was altered through the perturbation of ROS homeostasis by chemical treatments or suppression of ROS-scavenging proteins, along with the activating/suppressing the transcription of genes related to auxin transportation and signaling. These results show that stress responses are activated during S.E. and may regulate the ROS homeostasis by interacting with auxin signaling.

Organogenic nodule formation in hop: a tool to study morphogenesis in plants with biotechnological and medicinal applications

The usage of Humulus lupulus for brewing increased the demand for high-quality plant material. Simultaneously, hop has been used in traditional medicine and recently recognized with anticancer and anti-infective properties. Tissue culture techniques have been reported for a wide range of species, and open the prospect for propagation of disease-free, genetically uniform and massive amounts of plants in vitro. Moreover, the development of large-scale culture methods using bioreactors enables the industrial production of secondary metabolites. Reliable and efficient tissue culture protocol for shoot regeneration through organogenic nodule formation was established for hop. The present review describes the histological, and biochemical changes occurring during this morphogenic process, together with an analysis of transcriptional and metabolic profiles. We also discuss the existence of common molecular factors among three different morphogenic processes: organogenic nodules and somatic embryogenesis, which strictly speaking depend exclusively on intrinsic developmental reprogramming, and legume nitrogen-fixing root nodules, which arises in response to symbiosis. The review of the key factors that participate in hop nodule organogenesis and the comparison with other morphogenic processes may have merit as a study presenting recent advances in complex molecular networks occurring during morphogenesis and together, these provide a rich framework for biotechnology applications.

Instrumentation of biotechnological processes

Modern bioprocesses are monitored by on-line sensing devices mounted either in situ or externally. In addition to sensor probes, more and more analytical subsystems are being exploited to monitor the state of a bioprocess on-line and in real time. Some of these subsystems deliver signals that are useful for documentation only, other, less delayed systems generate signals useful for closed loop process control. Various conventional and non-conventional monitoring instruments are evaluated; their usefulness, benefits and associated pitfalls are discussed.

In vivo 31P and multilabel 13C NMR measurements for evaluation of plant metabolic pathways

Reliable measurements of intracellular metabolites are useful for effective plant metabolic engineering. This study explored the application of in situ 31P and 13C NMR spectroscopy for long-term measurements of intracellular pH and concentrations of several metabolites in glycolysis, glucan synthesis, and central carbon metabolic pathways in plant tissues. An NMR perfusion reactor system was designed to allow Catharanthus roseus hairy root cultures to grow for 3-6 weeks, during which time NMR spectroscopy was performed. Constant cytoplasmic pH (7.40+/-0.06), observed during the entire experiment, indicated adequate oxygenation. 13C NMR spectroscopy was performed on hairy root cultures grown in solutions containing 1-13C-, 2-13C-, and 3-13C-labeled glucose in separate experiments and the flow of label was monitored. Activities of pentose phosphate pathways, nonphotosynthetic CO2 fixation, and glucan synthesis pathways were evident from the experimental results. Scrambling of label in glucans also indicated recycling of triose phosphate and their subsequent conversion to hexose phosphates.

On-line measurement in biotechnology: Techniques

Bioprocesses are generally ill controlled. This is due to the fact that the measurement of relevant variables is difficult. Therefore, fundamental knowledge of metabolic interrelations is, at least in vivo, limited. In this article, some of the most important measurement techniques are reviewed in order to provide an evaluation of their current state. Emphasis is given to the underlying principles and on-line capability which allow to judge their importance and potential for exploitation resulting in well (maybe entirely) controlled bioprocesses in the future.