HSPs under Abiotic Stresses

Different organisms respond to the altered environmental conditions by different ways. Heat shock proteins’ (HSPs) production is one among the different defense mechanisms which defend the photosystem II and thylokoid membrane in plants. There are different types of HSPs based on their size, that is, high molecular weight (60–100 kDa) and low molecular weight heat shock proteins (15–30 kDa). Small HSPs are further classified based on their localization and role in different sub-cellular organelles. Cp-sHSPs are the chloroplast-specific small HSPs that protect the photosystem II and thylokoid membrane. A model to control the Cp-sHSPs in Chenopodium album has been put forward in this chapter. According to this model, Cp-sHSPs of Chenopodium album are created in cytoplasm and are moved toward chloroplast. The transit peptide is removed on reaching to the target sub-cellular organelle, that is, chloroplast and the premature Cp-sHSPs are converted into mature ones which have multiple roles under different abiotic stress conditions

Mechanisms of Signal Transduction by Ethylene: Overlapping and Non-Overlapping Signalling Roles in a Receptor Family

The plant hormone ethylene regulates growth and development as well as responses to biotic and abiotic stresses. Over the last few decades, key elements involved in ethylene signal transduction have been identified through genetic approaches, these elements defining a pathway that extends from initial ethylene perception at the endoplasmic reticulum to changes in transcriptional regulation within the nucleus. Here, we present our current understanding of ethylene signal transduction, focusing on recent developments that support a model with overlapping and non-overlapping roles for members of the ethylene receptor family. We consider the evidence supporting this model for sub-functionalization within the receptor family, and then discuss mechanisms by which such a sub-functionalization may occur. To this end, we consider the importance of receptor interactions in modulating their signal output and how such interactions vary in the receptor family. In addition, we consider evidence indicating that ethylene signal output by the receptors involves both phosphorylation-dependent and phosphorylation-independent mechanisms. We conclude with a current model for signalling by the ethylene receptors placed within the overall context of ethylene signal transduction

Tomato post-harvest fruit ripening in Pakistan : effect of methylcyclopropene (1-MCP) in inhibiting ripening gene expression

Short shelf life of tomato fruits, with the unavailability of modernized handling/storage and transport practices causes ~30-40 % of yield loss which leads to great financial burden on the import of Pakistani tomatoes. There is an urgent need to adapt an easy and cost effective applicable technology for increasing the shelf life of fully ripened tomato fruits by inhibiting ethylene perception that leads to ripening and decay. This study aims to evaluate the effectiveness of ethylene perception inhibitor 1-methylcyclopropene (1-MCP) on ripening of tomatoes. Physiological and molecular parameters were recorded to analyse the inhibitory effect of 1-MCP. Green tomatoes were harvested and treated with 1-MCP for 24 h and 8 days. Results of the physiological data based on colour, weight, and firmness of the fruits showed a significant delay in the onset of ripening after 1-MCP treatment. 1-MCP is known to block ethylene receptors, therefore, we used different ethylene and ripening related genes as markers to prove that 1-MCP potentially delayed tomato fruit ripening by inhibiting the ethylene pathway that in turn downregulated the ripening signalling pathway genes. Therefore, this study provides evidence that 1-MCP can effectively be used as an alternative to reduce the post-harvest tomato yield losses in Pakistan with slight optimization on the method to suit the different varieties of local tomatoes

The ARGOS Gene Family Functions in a Negative Feedback Loop to Desensitize Plants to Ethylene

Ethylene plays critical roles in plant growth and development, including the regulation of cell expansion, senescence, and the response to biotic and abiotic stresses. Elements of the initial signal transduction pathway have been determined, but we are still defining regulatory mechanisms by which the sensitivity of plants to ethylene is modulated. We report here that members of the ARGOS gene family of Arabidopsis, previously implicated in the regulation of plant growth and biomass, function as negative feedback regulators of ethylene signaling. Expression of all four members of the ARGOS family is induced by ethylene, but this induction is blocked in ethylene-insensitive mutants. The dose dependence for ethylene induction varies among the ARGOS family members, suggesting that they could modulate responses across a range of ethylene concentrations. GFP-fusions of ARGOS and ARL localize to the endoplasmic reticulum, the same subcellular location as the ethylene receptors and other initial components of the ethylene signaling pathway. Seedlings with increased expression of ARGOS family members exhibit reduced ethylene sensitivity based on physiological and molecular responses

Fatty acid profiling and physiochemical characterization of Chlorella sorokiniana potentially used for biofuel production

Rising oil prices and climate change have resulted in more emphasis on research into renewable biofuels. In this study, different water samples were collected from local vicinities for the isolation of local isolates of microalgae to check their potential towards the production of biofuel by the addition of different chemical substrates. Five different concentrations of ascorbic acid and iron (III) chloride (0, 1, 2.5, 5 & 10 µM) are used as substrates. Microscopic analysis evaluated that samples belong to genus Chlorella and further molecular identification showed that the samples are C. sorokiniana. Among all the concentrations of ascorbic acid 2.5 µM is most effective against the C. sorokiniana strain 1 (Safari Wildlife Park, Lahore) and C. sorokiniana strain 2 (Bahria Town, Lahore) while C. sorokiniana Strain 3 (SukhChane Society, Lahore) responded at 2.5 & 5 µM in term of biomass production. FeCl3 (2.5 µM) is effective against C. sorokiniana strain 1 while the growth of C. sorokiniana strain 2 and C. sorokiniana Strain 3 is inhibited. Lipid content analysis showed that only the C. sorokiniana strain 1 shows effective results at 1 & 2.5 µM of ascorbic acid and FeCl3 , respectively. Those concentrations which give the significant results of lipid production were preceded for fatty acid profiling. Results indicate that the C. sorokiniana strain 1 can be considered as a source of alpha-linolenic acid; the basic constituent of biofuel production. In this study, it is concluded that C. sorokiniana strain 1 is useful for the production of environment friendly biofuel

In vitro evaluation of biological activities of citrus leaf extracts

Leaves extracts of three different citrus species namely Citrus sinensis (Malta), Citrus paradisi (Grape fruit) and Citrus jambhiri (Khatti) were evaluated for their antioxidant, cytotoxic, antitumor, antimicrobial activities and finally the mineral contents were determined. Four types of extraction solvents (100, 80 and 50% methanol and distilled water heated at 50oC) were used for extraction of antioxidant compounds. Extracts yield increased with the elevated levels of aqueous component of organic solvent and our data showed the highest yield in aqueous extracts. All extraction regimes showed in vitro antioxidant activity. Citrus paradisi showed the highest total flavonoid content (TFC), total phenolic content (TPC), reducing power and 1,1-Diphenyl-2- picrylhydrazil free radical scavenging activity in all combinations of solvents followed by Citrus sinensis and Citrus jambhiri. Antioxidant activity was also increased with higher aqueous component of organic solvents in each case. While Citrus sinensis (in 100% methanolic solvent) and Citrus paradisi (in 50% methanolic extract) showed significant cytotoxicity (LD50 values <1000). Antitumor activity was observed in all extracts, however Citrus sinensis and Citrus paradisi (in 50% aqueous methanolic) extracts had the highest antitumor activity from the selected citrus species whereas no antimicrobial activity was observed at higher concentrations (4000 μgmL-1) against specified strains. We found high calcium contents in all three citrus species tested by atomic absorption method. The results showed that the leaves of selected Citrus species possess significant antioxidant, antitumor and cytotoxic activities. Citrus leaves extracts can be potentially helpful in antioxidant protection in food as well as in human body against lipid peroxidation and free radicals damage. It can further be evaluated after in vivo studies using animal models or identifications of high throughput methods for enhanced biological activities

Mutational analysis of various sub genomic regions of HCV and their role in interferon therapy response

Combination therapy with interferon (IFN) and ribavirin for 24 to 48 weeks is the current standard treatment for chronic hepatitis C. Success rate is 67-80%. There are four subgenomic regions of HCV in which distinct mutations have been observed in response to IFN therapy; E2-PePHD, NS5A- ISDR, NS5A-PKRBD and NS5A-V3 domains. Current meta analysis gives comprehensive details of mutations in subgenomic regions and their role in non responsiveness to IFN treatment. It has been observed that E2-PePHD region is well conserved region and show high sensitivity to IFN-ribavirin tiherapy. The substitutions within the NS5A-ISDR to the treatment outcome are conflicting. Mutations within the NS5A-PKRBD of HCV type 1 are associated with a long-term sustained response to IFN-ribavirin therapy. There is a considerable association between efficacy of treatment and a high mutation rate within NS5A-V3 domain has been observed. There are also other domains of HCV i.e. IRRDR, CRS and NLS, but no significant mutations been studied in these regions, more research is to be required

Screening of rice varieties based on remodeling of root architecture linked to enhanced phosphorus transporters and ethylene signaling for better phosphorous acquisition under limiting conditions

Root architectural modifications in response to altered nutrient level can be used as selection marker for better adapted rice varieties. In this study, we screened six local rice varieties commonly grown in Pakistan, using their unique root architecture and several molecular markers to identify best adapted local variety under phosphorus limiting conditions. Our data showed that rice variety with significant changes in its three-dimensional root architecture system (RSA) and enhanced expression of phosphorus transporters (OsPT2, OsPT4 and OsPT6) is the best variety to handle stress as compared to other varieties. Along with development of screening strategy/method, our data provided evidence that phosphorus starvation leads to upregulation of stress hormone ethylene, which regulates root elongation and root hair development therefore facilitating root architecture modification. We then further checked, how to mitigate or enhance phosphorus starvation responses by application of hormones exogenously, our results showed that ethylene application/ treatment enhances phosphorus starvation responses, whereas cytokinin on the other hand reverses deficiency effects which implicates hormonal cross talk is key to modulate P-deficiency responses in rice. This study provides an easy and quick method of analysis of root architecture as physiological marker for rice screening and improve crop yield by selecting best adapted variety for P deficient soils. In future, detail study for understanding phytohormone mediated transcriptomic changes in response to nutrient deficiency and in correlation with physiological response will help to select better adapted varieties that will eventually result in increase of rice yield

Histidine Kinase Activity of the Ethylene Receptor ETR1 Facilitates the Ethylene Response in Arabidopsis1[W][OA]

In Arabidopsis (Arabidopsis thaliana), ethylene is perceived by a receptor family consisting of five members. Subfamily 1 members ETHYLENE RESPONSE1 (ETR1) and ETHYLENE RESPONSE SENSOR1 (ERS1) have histidine kinase activity, unlike the subfamily 2 members ETR2, ERS2, and ETHYLENE INSENSITIVE4 (EIN4), which lack amino acid residues critical for this enzymatic activity. To resolve the role of histidine kinase activity in signaling by the receptors, we transformed an etr1-9;ers1-3 double mutant with wild-type and kinase-inactive versions of the receptor ETR1. Both wild-type and kinase-inactive ETR1 rescue the constitutive ethylene-response phenotype of etr1-9;ers1-3, restoring normal growth to the mutant in air. However, the lines carrying kinase-inactive ETR1 exhibit reduced sensitivity to ethylene based on several growth response assays. Microarray and real-time polymerase chain reaction analyses of gene expression support a role for histidine kinase activity in eliciting the ethylene response. In addition, protein levels of the Raf-like kinase CONSTITUTIVE TRIPLE RESPONSE1 (CTR1), which physically associates with the ethylene receptor ETR1, are less responsive to ethylene in lines containing kinase-inactive ETR1. These data indicate that the histidine kinase activity of ETR1 is not required for but plays a modulating role in the regulation of ethylene responses. Models for how enzymatic and nonenzymatic regulation may facilitate signaling from the ethylene receptors are discussed