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

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

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.</jats:p

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