Essay Example on Continuous multiplication and urbanization of the human population









Continuous multiplication and urbanization of human population have prompted broad progression in the anthropogenic and technogenic processes e g mining metallurgical operations car industries paper and pulp production tanning wood preservation electroplating and novel agronomical works including different agrochemicals Ahemad 2015 Because of these continuous and ceaseless procedures a prolific release of heavy metals as by products has to lead to significant contamination of soils and water Quaggiotto et al 2007 Cd Cr Pb Al Hg etc are some non essential heavy metals that don't have a physiological function but they are very toxic even at very low concentrations Garzón et al 2011 Gill et al 2013 Singh et al 2016 Generally heavy metals of biological importance are divided into two categories of redox active metals such as Cr Mn Cu and Fe and non redox active metals such as Cd Al Hg Ni and Zn according to their physicochemical characteristics Emamverdian 2015 Bucker Neto 2017 Shahid 2014 karimi and Khataee 2012 The redox metals can straightly produce ROS or oxygen free radicals species in plants via Haber Weiss and Fenton reactions Jozefczak et al 2012 A specific example of a heavy metal contaminant is Cr It is one of the nonessential metallic elements which is a part of the first transition series in the periodic table Ahmad and Misra 2014 and exists in two distinct states hexavalent chromium Cr 6 and trivalent chromium Cr 3 Cr 6 which exists as an oxyanion at physiological pH is soluble highly mobile very unstable and more toxic than Cr 3 Eleftheriou et al 2015 

Over the most recent years due to urban and industrial activities the number of Cr contaminated sites has increased and hence Cr pollution has attained considerable attention being regarded as a major region of concern around the world Quaggiotto et al 2007 but in some recent experimental studies it was showed that higher concentrations of heavy metals can promote the production of secondary metabolites which have therapeutic activities in medicinal plants Wójciak Kosior et al 2016 Rai et al 2014 Srivastava and Srivastava 2010 Sinha and Saxena 2006 Rai et al 2005 So it was proposed that we can use wastelands contaminated with heavy metals for growing some valuable medicinal plants to increase the active constituents of them Plants which are used in the modern drug industry and particularly have a lower percentage of active constituents may be selected for such type of study Catharanthus roseus L is an important medicinal plant of the family apocynaceae that contains more than 130 alkaloids of the indole group named TIAs out of which 25 are dimeric in nature and have activities like antidiabetic bactericide antihypertensive and anti cancerous Rai et al 2014 Vinblastine and vincristine are two of the dimeric alkaloids that chiefly exist in the aerial parts They are potent antineoplastic agents and indispensable constituents of most cancer chemotherapies Shukla et al 2006 C roseus is also the source of two other medicinal TIAs ajmalicine and serpentine identified as antihypertensive and sedative compounds respectively Guimaraes et al 2012 which are main ingredients of medicines applied for controlling high blood pressure and other kinds of cardiovascular diseases Ncube and Staden 2015 Plants are the only source of these alkaloids Vernay et al 2008 

The high pharmacological significance of the TIAs and their low amounts in the plant around 0 0005 of dry weight has motivated wide research on the TIA pathway for manipulating plant metabolism to enhance amounts of alkaloids Guimaraes et al 2012 In addition to methods such as environmental stresses like pathogen attack UV irradiation high light wounding nutrient deficiencies and temperature a number of researchers as mentioned above have applied various heavy metal treatments in cultures of plant cell tissue and organ to increase the production or to induce de novo synthesis of secondary metabolites in in vitro plant cell cultures Akula and Ravishankar 2011 Sivanandhan et al 2014 Use of a heavy metal not only accumulate the secondary metabolites but also activates the pathways related to defense system by which they mediate the deleterious effects of the ROS Such defense systems involve both enzymatic and non enzymatic antioxidants Panda 2007 The plant hormone jasmonic acid JA and its methylated form Mj are key elements of plant s immune system that regulate the protective reactions against stresses Pieterse et al 2012

There are a lot of studies that show the exogenous application of Mj participates in signal transduction chain and results in high biosynthesis of TIAs in C roseus Akula and Ravishankar 2011 Goldhaber Pasillas et al 2014 Van Moerkercke et al 2015 To respond biotic and abiotic stresses signal transduction and transcriptional regulation are fundamental The key enzymes of the pathway and transcription factors TFs affecting their activity and regulatory pathways have always been considered The manifest example of this subject is the jasmonate inducible AP2 ERF APETALA2 ethylene responsive factor domain TF ORCA3 that is a key regulator of several important genes in TIA pathway and induces its effect via binding to a jasmonate and elicitor responsive element JERE in the promoter of biosynthetic genes Raina et al 2012 Zhang et al 2011 In addition to TFs MAPK cascades upstream of these factors are important in the regulation of pathway and production of important TIAs under several abiotic stress conditions For example C roseus in response to UV and wounding treatments and also Mj application exhibited an enhanced MAPK3 transcripts accumulation and activity Also overexpression of MAPK3 caused the up regulation of ORCA3 and the transcripts of genes involved in TIA biosynthesis pathway Mujib et al 2012 Trinh et al 2014

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