TRANSCRIPTOMIC AND METABOLOMIC ANALYSIS OF GROUNDNUT (Arachis hypogaea L.) UNDER VARYING TEMPERATURE 2320
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Date
2017-06
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JUNAGADH
Abstract
Key word: Enzyme, Expression profile, GC-MS, Groundnut, KEGG pathways, LC-MS/MS, Phenolics, Polyamines, RT-PCR, Temperature stress.
Groundnut (Arachis hypogaea L.) an important oilseed and food legume crop of tropical and subtropical world. Groundnut genotypes ICGS44 (High temperature tolerant), GG7 and AK159 (Moderately tolerant to high temperature) and KRG1 (High temperature sensitive) were grown in low, normal and high temperature as different date of sowing in field condition during Rabi-Summer-2015.
Whole-transcriptome analysis is very important to understand altered expression of genetic variants that contribute to complex plant phenotypes. Differential expression analysis in transriptomic study revealed various stress induced genes like HSP90, MDH, NIA, LOX were expressed and distinguished in ICGS44 and in KRG1. All these genes may confer temperature stress tolerance to respective genotypes. Gene ontology analysis suggested that top-hit species distribution was found similar to Spinacia oleracea, Nicotiana tobacum, Pisum sativum and Gossypium hirsutum in ICGS44 and Pisum sativum in KRG1 at low temperature. While at normal and higher temperature top-hit species distribution was found similar to Pisum sativum in both ICGS44 and KRG1. KEGG pathway analysis suggested that total 107 pathways were identified in ICGS44 and 122 pathways were identified in KRG1 at low temperature, total 30 in ICGS44 and 95 in KRG1 at normal temperature and total 137 and 138 pathways were identified in ICGS44 and KRG1, respectively at high temperature. Among them some unique pathways were also found. Almost all the unique pathways (except mucin type O-glycan biosynthesis) might play important role in high temperature tolerance mechanism by different mechanism for e.g. by producing ROS as signaling molecule, or by producing antioxidant, involving in rearrangement of extracellular matrix, etc. Gene expression analysis revealed that HSP40, LOX1, POD, OrDec, SMS and SpsS were upregulated at high temperature while, SOD, POD, AMO and ACCO were upregulated during low temperature.
Metabolomic studies have demonstrated that active reconfiguration of the metabolome is regulated in part by changes in gene expression initiated by temperature-stress-activated signaling and stress-related transcription factors. Metabolomic study suggested several metabolites produced in individual genotype may confer tolerance to temperature stress. Among which higher sugar accumulation provides energy and sugar alcohols can functions as osmolytes to maintain turger pressure of the cell. Stress induced metabolites like polyamines and phenolics, clearly showed pattern of their production at different temperature. Polyamines accumulation increased at low as well as at high temperature while phenolics produced at lower temperature in high concentration. Both of them might function as stress regulatory mechanism. Enzyme assay revealed their better function at normal temperature. All the enzymes studied i.e. malate dehydrogenase, citrate synthase, phenylalanine ammonia lyase and nitrate reductase showed enhanced activities in ICGS44 suggesting its temperature tolerance nature.
Overall expression of HSP90, CAT1, MDH1 genes and some metabolites like Beta-D-galactofuranoside, l-threonine, hexopyranose, D-glucopyranose, stearic acid, 4-ketoglucose, gulose, 2-O-glycerol-.alpha.-d-galactopyranoside, linolenic acid, serine and enzymes nitrate reductase, citrate synthase, malate dehydrogenase and phenylalanine ammonia lyase confer high temperature tolerance to ICGS44.
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biochemistry