Elucidating the Cellular Physiology Associated with the Herbicide (Glyphosate) Resistance and Tolerance in Agricultural Weeds Using Metabolomics Approach

Current management practices overemphasizes on herbicides to manage weeds in crop production systems. However, indiscriminate use of herbicides to manage weeds has resulted in the development of resistance in several weed biotypes. Over-application on glyphosate to manage weeds in cropping system that uses RoundUp® Ready™ trait has resulted in the dominance of glyphosate resistant weeds across cropping systems. Glyphosate resistance is an important, economically unviable and rapidly escalating problem across agricultural production systems. To combat herbicide resistance, current recommendations advocate for changes in chemical and cultural practices of weed control, including rotation of herbicide regimen with herbicides with alternate modes of action, and formulation of cultural practices that would penalize the expression of resistance. Some of the bottlenecks in practicing these approaches are the current lack of knowledge about the weed cellular physiology that ensues resistance expression, the potential metabolic cost associated with this resistance expression, and the occurrence of compensatory pathways that could defray the cost of resistance expression. Adopting an alternate herbicide regimen without an understanding of the cellular physiology of resistance expression would result in the development of herbicide cross resistance in weeds, which would further aggravate the problem. To bridge this knowledge-gap, in this studies, metabolomics approach and complementary biochemical analyses were used to track the changes in cellular metabolism in weed species and biotypes that are resistant and naturally tolerant to glyphosate. In Ipomoea lacunosa, non-targeted metabolic profiling captured the differences in metabolic pool levels in two biotypes (WAS and QUI) with contrasting glyphosate tolerance (GR50 = 151 g ae ha-1 and 59 g ae ha-1). Metabolic profiling followed by pathway topological analysis captured innate metabolic differences (22 significantly different metabolites) between WAS and QUI biotypes. Despite the glyphosate dose being half the GR50 rate, shikimic acid accumulation was observed in both the biotypes. However, regardless of EPSPS inhibition, no changes in aromatic amino abundance was observed in the QUI biotype and WAS biotype, indicating their tolerance to the glyphosate. The results from this study implies that though I. lacunosa is tolerant to glyphosate, glyphosate exposure induces cellular metabolic perturbations. The varying tolerance to glyphosate could thus be due to physiological and metabolic adaptations between the different biotypes. Following through, metabolite and biochemical profiling of a susceptible (S) and resistant (R) biotype of Amaranthus palmeri identified physiological perturbations induced by glyphosate in both the biotypes at 8 and 80 hours after treatment (HAT). Compared to the S-biotype, the R-biotype had a 17 fold resistance to the normal field recommended rate of glyphosate. At 8HAT, shikimic acid accumulation in both S- and R-biotypes in response to glyphosate application indicated that the R-biotype was equally susceptible to glyphosate toxicity. The metabolite pool of glyphosate-treated R-biotype was similar to that of the water-treated (control) S and R-biotype, indicating physiological recovery at 80 HAT. A key finding from this study is that despite being resistant to glyphosate, Palmer amaranth biotypes initially sustained metabolic perturbation from glyphosate. However, what differentiates them from the susceptible biotypes is their ability to recover from the glyphosate induced metabolic disruptions. In response to glyphosate, glyphosate-treated R-biotype had lower reactive oxygen species (ROS) damage, higher ROS scavenging activity, and higher levels of secondary compounds of the shikimate pathway, leading to the finding that elevated anti-oxidant mechanisms in A. palmeri complements the resistance conferred due to increased EPSPS copy number. Furthermore, metabolite dynamics in response to glyphosate application studied using stable isotope resolved metabolomics revealed that despite glyphosate toxicity induced decrease in soluble proteins, a proportional increase in both 14N and 15N amino acids was observed in the susceptible plants. This indicates that following glyphosate treatment, a potential increase in de novo amino acid synthesis, coupled with a lower protein synthesis, and higher protein catabolism is observed in the S-biotype. In contrast, the R-biotype, though affected by glyphosate initially, had higher de novo amino acid synthesis without significant disruptions. Moreover, it is to be noted that although the initial assimilation of inorganic nitrogen to organic forms is less affected in the S-biotype than the R-biotype by glyphosate, amino acid biosynthesis downstream of glutamine is disproportionately disrupted. It is thus concluded that the herbicide-induced amino acid abundance in the S-biotype is contributed to by both protein catabolism, and de novo synthesis of amino acids such as glutamine and asparagine. Due to variability in the genetic makeup of populations, each biotype would exhibit different physiological manifestations when exposed to the same rate of glyphosate. Biochemical and metabolic profiling of five different Palmer amaranth biotypes indicated that both the S- and R-biotypes had comparable innate phytochemical profile and similar abundance in flavonoids and phenolic. However, compared to the S-biotypes, the R-biotypes had innately higher anti-oxidant capacity, and the antioxidant capacity was observed to correlate with the GR50 such that antioxidant capacity increased with increasing GR50. Upon treatment with glyphosate, there were significant alterations in the metabolic pool levels across all biotypes. After glyphosate treatment, the content of total phenolic and flavonoids decrease in S-biotypes, whereas the abundance of these metabolites either remained the same, or increased in the R-biotypes. These results indicate that antioxidant capacity is a complementary function aiding in conferring glyphosate resistance and the phytochemistry and the antioxidant capacity is partly induced after glyphosate application, rather than being constitutively expressed. Overall, these study demonstrates that, across biotypes and species, irrespective of their degree of resistance/tolerance, glyphosate not only perturbs shikimate pathway, but also a multitude of other metabolic pathways that are independent of shikimate pathway (secondary toxic effects) as early as eight hours after treatment. While in the susceptible biotypes these metabolic perturbations result in rapid cellular damage, these metabolic perturbations fail to translate to cellular damage in the resistant biotypes. The results indicate that the resistance of A. palmeri biotypes that were used in these studies partially stems from their ability to rapidly induce the production of phenylpropanoids soon after the glyphosate application. This induction of phytochemicals could quench the reactive molecules that are initially produced during the secondary metabolic perturbations, and would thus complement the glyphosate resistance in Amaranthus biotypes conferred by EPSPS gene amplification

Green Finance: The Future of Sustainable Banking in India

India is now in a situation where it has to accept the challenges from the international forum to improve its green infrastructure and attain its sustainable developments goals and climatic challenges like global warming, its huge population and huge green depletion. If the country has to survive it has to adopt Green finance. Green finance or climate finance is a component where it has to change it’s focus and behaviour from traditional form of financing to more environment friendly financing. It has to build a strategy through green finance to achieve its sustainable development goals. Indian and international financial agencies, corporates need to be encouraged to refocus on the aspect of green finance. There has been lot of promises and challenges in this front. This study is an effort to understand the situation where India stands and the go ahead as far as green finance and to manage its sustainable development goals. This study is of descriptive in nature and is based on secondary data derived from various international and national agency reports, which includes report from Government of India

Impact of GDP volatility on current account balances

This paper empirically investigates the impact of GDP volatility on current account balances for a large sample of developed and developing countries. We extend the standard set of short- and long-term determinants of current accounts to include GDP volatility computed from the annual growth rate of GDP. It turns out that for low income countries the impact of GDP volatility on their current account balances is negative, whereas the reverse is true for high income countries. The intertemporal approach to the balance of payments followed in this paper suggests that a diverse response of current account balances to GDP volatility can be due to the different degree of shock persistence in developed and developing countries.current account, savings, investment, volatility

Glyphosate Application Causes Physiological Perturbations in Amino Acid Profiles of Palmer amaranth- A Study of Susceptible and Resistant Biotypes of Amaranthus palmeri

Glyphosate is the most widely used herbicide in the world. It is used to control perennial grasses and weeds having broad leaves. Glyphosate works by inhibiting the plant specific enzyme 5-enolpyruvylshikimate-3-phospate synthase that catalyzes the conversion of shikimic acid to chorismate, which serves as the precursor to production of aromatic amino acids, namely tyrosine, phenylalanine and tryptophan

Crack nucleation, growth & arrest under subcritical crack growth

Crack nucleation (and growth) can be characterized under static load (or cyclic loads) in the presence of an environment. Chemically assisted cracking is occurs when stresses to nucleate (or propagate cracks) are much lower fracture of a material in an inert (like in vacuum) environment where a material is free from the damaging chemical environment. Similarly, embrittlement occurs if chemically active elements are dispersed internally as in internal hydrogen, metalloids and other embrittling elements. The materials where such embrittlement phenomena occurs are also divergent: pure metals, alloys, and ceramics or glasses. Since materials are used in applications involve various chemical environments under load, the importance of understanding the role of environment in material performance need not be stressed. In fact, there are many analyses in the past highlighting the divergent behaviors in each of the systems and environments emphasizing the specialties specific to a given material/environment system. In addition, many efforts have been made in the past to arrive at some unifying principles governing the embrittlement phenomena. An inescapable conclusion reached on this topic by many is that the behavior is very “complex”. Hence, recognizing the complexity of material/environment behavior, we focus our attention, mainly on metallic systems, in extracting some similarities to arrive at some generic principles involved. The ultimate goal of this effort is to arrive at some self-consistent scheme for incorporating “chemical effects” into a life prediction model for components in service

Unified approach to crack growth and fracture

Unified approach connects the behavior of a smooth specimen, of a notched specimen and of the fracture-mechanics specimen, under inert and corrosive environments, using the unifying principles and the Modified Kitagawa-Takahashi Diagram. The unifying principles are based on the fact that the behavior of short cracks is not different from that of long cracks, and the same thresholds govern the crack growth. Cracks being high energy defects, local internal stresses are required to initiate and grow the cracks in all cases. The internal stresses can be pre-existing as in the case of long cracks or in situ generated or augmented in the case of smooth and notched specimens. Observed variations in the crack growth rates of short cracks from those of long cracks arise due to variations in the types and degrees of pre-existing internal stresses. In aggressive environments, chemical forces provide additional driving forces over and above the mechanical forces. Chemical forces come from the chemical and/or electro chemical potential gradients which may be difficult to determine as they depend on the nature and the extent of the local chemical reactions in the changing compositional gradients. From practical considerations, we show that they can be quantified using the inert medium as a reference. Cyclic loads provides additional factors since crack tip driving forces come from both monotonic and cyclic loads leading to load-ratio R dependence. We provide here a systematic analysis of these factors using our Unified Approach to help in quantification and codification of the kinetics of the crack growth and fracture

Liquidity-Profitability Trade-off in Commercial Banks: Evidence from Tanzania

This paper examines the relationship between banks’ profitability and liquidity by using three different models. It is a longitudinal study whereby five banks from Tanzania were taken into consideration for the time period from year 2006 to 2013. By using Hausman test and thereafter fixed effects approach, all the models revealed that there is no statistically significant relationship between banks’ profitability and liquidity. Thus, it can be concluded that the banks can focus on increasing their profitability without affecting their liquidity, and vice versa. However, this is not guaranteed because the situation might change or one might come out with different kind of results if a different sample is used. Keywords: Liquidity, Profitability, Commercial banks, Tanzani

Initiation and growth of corrosion fatigue cracks from corrosion pits using elasto-plastic notch analysis

Corrosion pits are known to act as precursors for fatigue crack initiation under corrosive environment. The transition from pit to crack growth under corrosion fatigue is of considerable interest for many engineering structures. Several predictive methodologies have been developed. As the Pits grow with large aspect ratio, they behave like local stress/strain concentrations accentuating the crack initiation and growth. In this paper, we extend our recent analysis of crack initiation at the elastic-plastic notch tip stress fields* to evaluate its applicability to pit to crack transition. Ref: K. Sadananda, A. Arcari, A.K. Vaudevan, Eng. Frac. Mech., 2017, 176 pp.144-16