Signal transduction and biotechnology in response to environmental stresses

Providing sufficient food to burgeoning population from the steadily shrinking arable land seems to be very difficult in near future and is one of the foremost challenges for plant scientists. In addition, there are several biotic and abiotic stresses which frequently encounter crop plants during various stages of life cycle, resulting in considerable yield losses. Environmental stresses, including drought, flooding, salinity, temperature (both low and high), high radiation, and xenobiotics induce toxicity, membrane damage, excessive reactive oxygen species (ROS) production, reduced photosynthesis, and altered nutrient acquisition. Several indigenous defence mechanisms (physiological and molecular) are triggered in plants on exposure to environmental cues. Enhancement of resistance of crop plants to environmental stresses has been the topic of prime interest for agriculturalists and plant scientists since long. Development of water and salinity stress-tolerant crops through genetic engineering provides an avenue towards the reclamation of farmlands that have been lost due to salinity and lack of irrigation water/rainfall. Understanding the complexity of stress tolerance mechanisms in orthodox or model plants at the genetic and molecular levels improves feasibility of enhancing tolerance of sensitive crop plants.     

Model-based translation of DNA damage signaling dynamics across cell types

Interindividual variability in DNA damage response (DDR) dynamics may evoke differences in susceptibility to cancer. However, pathway dynamics are often studied in cell lines as alternative to primary cells, disregarding variability. To compare DDR dynamics in the cell line HepG2 with primary human hepatocytes (PHHs), we developed a HepG2-based computational model that describes the dynamics of DDR regulator p53 and targets MDM2, p21 and BTG2. We used this model to generate simulations of virtual PHHs and compared the results to those for PHH donor samples. Correlations between baseline p53 and p21 or BTG2 mRNA expression in the absence and presence of DNA damage for HepG2-derived virtual samples matched the moderately positive correlations observed for 50 PHH donor samples, but not the negative correlations between p53 and its inhibitor MDM2. Model parameter manipulation that affected p53 or MDM2 dynamics was not sufficient to accurately explain the negative correlation between these genes. Thus, extrapolation from HepG2 to PHH can be done for some DDR elements, yet our analysis also reveals a knowledge gap within p53 pathway regulation, which makes such extrapolation inaccurate for the regulator MDM2. This illustrates the relevance of studying pathway dynamics in addition to gene expression comparisons to allow reliable translation of cellular responses from cell lines to primary cells. Overall, with our approach we show that dynamical modeling can be used to improve our understanding of the sources of interindividual variability of pathway dynamics.     

Aspergillus fumigatus AR04 obeys Arrhenius' rule in cultivation temperature shifts from 30 to 40°C

To set a benchmark in fungal growth rate, a differential analysis of prototrophic Aspergillus fumigatus AR04 with three ascomycetes applied in > 10³ t year^-1 scale was performed, i.e. Ashbya gosspyii (riboflavin), Aspergillus niger (citric acid) and Aspergillus oryzae (food-processing). While radial colony growth decreased 0.5-fold when A. gossypii was cultivated at 40°C instead of 28°C, A. fumigatus AR04 responded with 1.7-fold faster hyphal growth. A. niger and A. oryzae formed colonies at 40°C, but not at 43°C. Moreover, all A. fumigatus strains tested grew even at 49°C. In chemostat experiments, A. fumigatus AR04 reached steady state at a dilution rate of 0.7 h^-1 at 40°C, 120% more than reported for A. gossypii at 28°C. To study mycelial growth rates under unlimited conditions, carbon dioxide increase rates were calculated from concentrations detected online in the exhaust of batch fermentations for 3 h only. All rates calculated suggest that A. fumigatus AR04 approximates Arrhenius’ rule when comparing short cultivations at 30°C with those at 40°C. Linearization of the exponential phase and comparison of the slopes revealed an increase to 192% by the 10°C up-shift.     

Hydrogen sulfide alleviates chromium stress on cauliflower by restricting its uptake and enhancing antioxidative system

The present study evaluated the physiological and biochemical mechanisms through which exogenous sodium hydrosulfide (H₂S donor) mitigates chromium (Cr) stress in cauliflower. The different levels of Cr included 0, 10, 100 and 200 µM. Results reported that Cr exposure reduced growth and biomass, chlorophyll (Chl) contents, gas exchange parameters and enzymatic antioxidants. Chromium stress enhanced the production of electrolyte leakage (EL), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents and increased Cr content in the roots, stem, leaf and flowers. Exogenous H₂S improved the physiological and biochemical attributes of Cr-stressed cauliflower. Hydrogen sulfide decreased Cr content in different parts of Cr-stressed plants, whereas it increased the Chl contents and gas exchange attributes. H₂S reduced the EL, H₂O₂ and MDA concentrations, enhancing the antioxidant enzymes activities in Cr-stressed roots and leaves compared to the Cr treatments alone. Collectively, our results provide an insight into the protective role of H₂S in Cr-stressed cauliflower and suggest H₂S as a potential candidate in reducing Cr toxicity in cauliflower and other crops.     

Hotspot identification in the Indonesian tempeh supply chain using life cycle assessment

The International Journal of Life Cycle Assessment - Tempeh is a traditional Indonesian fermented soybean product, which plays an essential role in its culture and economy and forms an important...     

Silicon (Si) Supplementation Alleviates NaCl Toxicity in Mung Bean [Vigna radiata (L.) Wilczek] Through the Modifications of Physio-biochemical Attributes and Key Antioxidant Enzymes

Journal of Plant Growth Regulation - Mung bean is an important pulse crop. It is highly nutritive but is vulnerable to salinity stress. Therefore, the present study was aimed to investigate the...     

Zinc application mitigates the adverse effects of NaCl stress on mustard [Brassica juncea (L.) Czern & Coss] through modulating compatible organic solutes,antioxidant enzymes,and flavonoid content

This study examined the protective effect of Zn on salt-stressed Brassica juncea plants using some key morphological and biochemical attributes at different developmental stages (30, 60, and 90 days after treatment [DAT]). Salt stress (200?mM) caused suppression in plant height, root length, and dry weight by 58.35%, 41.15%, and 53.33%, respectively, at 90 DAT, but Zn application improved these variables by 15.52%, 16.59%, and 11.45%, respectively. Furthermore, 200?mM NaCl decreased total chlorophyll by 45.32% and relative water content by 27.62% at 90 DAT, whereas Zn application compensated the decrease in the levels of both variables. NaCl (200?mM) increased H₂O₂, malondialdehyde, and electrolyte leakage by 70.48%, 35.25%, and 68.39%, respectively, at 90 DAT, but Zn supplementation appreciably reduced these variables. Except for catalase, enzymatic antioxidant activity increased under NaCl stress. Zn application with salt further increased the activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione-S-transferase by 33.51%, 9.21%, 10.98%, 17.46%, and 12.87%, respectively, at 90 DAT. At 90 DAT, salt stress increased flavonoids by 24.88%, and Zn supply by a further 7.68%. Overall, Zn mitigated the adverse effects of salt stress through osmotic adjustment, as well as by modulating the oxidative defense system and flavonoid contents.     

Castasterone and Citric Acid Supplementation Alleviates Cadmium Toxicity by Modifying Antioxidants and Organic Acids in Brassica juncea

Journal of Plant Growth Regulation - Brassinosteroids are known to manage various stresses including heavy metals in plants and castasterone is a bioactive form of brassinosteroids. Citric acid, a...     

Over expression of PQQ glucose dehydrogenase in Escherichia coli under holo enzyme forming condition

Summary The over expression of PQQ glucose dehydrogenase PQQGDH was investigated. The level of PQQGDH expressed in E.coli PP2418/pGEc1 was more than 10 fold when the cultivation was carried out under holo enzyme forming condition in the presence of 600 nM of PQQ and 10 mM of MgCl₂, compared with those of apo condition. It may be due to the difference in thermal stability of apo and holo PQQGDH.