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Melatonin is a naturally occurring biologically active amine produced by plants, animals and microbes. This review explores the biosynthesis of melatonin in plants, with a particular focus on its diverse roles in Arabidopsis thaliana, a model species. Melatonin affects abiotic and biotic stress resistance in A. thaliana. Exogenous and endogenous melatonin is addressed in association with various conditions, including cold stress, high light stress, intense heat and infection with Botrytis cinerea or Pseudomonas, as well as in seed germination and lateral root formation. Furthermore, melatonin confers stress resistance in Arabidopsis by initiating the antioxidant system, remedying photosynthesis suppression, regulating transcription factors involved with stress resistance (CBF, DREB, ZAT,CAMTA,WRKY33, MYC2, TGA) and other stress-related hormones (abscisic acid, auxin, ethylene, jasmonic acid and salicylic acid). This article additionally addresses other precursors, metabolic components, expression of genes (COR, CBF, SNAT, ASMT, PIN, PR1, PDF1.2 and HSFA) and proteins (JAZ, NPR1) associated with melatonin and reducing both biological and environmental stressors. Furthermore, the future perspective of melatonin rich agri-crops is explored to enhance plant tolerance to abiotic and biotic stresses, maximise crop productivity and enhance nutritional worth, which may help improve food security. [ABSTRACT FROM AUTHOR]

Glycosyltransferases are ubiquitous enzymes play vital role in numerous aspects of living organisms and are involved in secondary metabolism. Also known as uridine diphosphate (UDP) glycosyltransferases (UGTs) are engaged in detoxification in living organisms. UGT76E1 is a member of 76E family of UGT comprising of 453 amino acids. The gene for glycosyltransferase, UGT76E1 from Arabidopsis thaliana was expressed and purified through affinity chromatography.Site directed mutagenesis was performed to change hydrophilic threonine (T) into hydrophobic alanine (A) at 134 position. Afterwards the activity of mutant enzyme was analyzed through mass spectrometry. Novobiocin and kaempherol were used as acceptor moleculesfor activity tests. After mutagenesis the mutant UGT76E1T134A lost its activity with its donor sugar UDP glucose, as no peak was observed for the required products glc-novobiocin and glc-kaempherol at 773 and 447 in mass spectrum respectively. The mutant did not attainany new activity with UDP rhamnose also. Complete loss of activity of UGT76E1T134A with UDP glucose as donor sugar suggested for the presence of significant peptides at the site of mutation.The current results showed that glycosyltransferases can be modified to use different substrates by site directed mutagenesis. This UGT enzyme modification could open new horizon in the development of new drugs for cancer treatment. © 2015 Friends Science Publishers [ABSTRACT FROM AUTHOR]