Transcriptomic Investigations Of Gene Networks In response To Arsenic Accumulation In Brassica Juncea L Czern and Coss

Abstract

iv newlineABSTRACT newlineTranscriptomic investigations of gene networks in response to arsenic newlineaccumulation in Brassica juncea (L.) Czern and Coss newlineName of student : Sapna Thakur newlineRegistration number : CUPB/MPh-PhD/SBAS/BIO/2012-13/01 newlineDegree for which submitted : Doctor of Philosophy newlineName of supervisor : Dr. Pankaj Bhardwaj newlineName of Centre : Centre for Biosciences newlineName of School : School of Basic and Applied Sciences newlineKeywords : Arsenic, Cadmium, Brassica juncea, newlinePhytoremediation, Transcriptome, and Pathway newlineanalysis newlineArsenic (As), a widespread toxic metalloid is class I carcinogen known to cause newlineadverse health effects in human. In the present study, As accumulation potential and newlinedifferential gene expression in B. juncea is investigated. The amount of arsenic newlineaccumulated varied in the range of 15.99 to 1138.70 mg/Kg on dry weight basis in newlinefive cultivars. A decrease in chlorophyll content and increase in membrane damage newlineand enzymatic activities of antioxidants was observed with increase in As newlineconcentration in the B. juncea cultivars. Using maximum As accumulating cultivar newline(RLM514), a total of 10,870 significantly differentially expressed transcripts in newlineresponse to As treatment were identified. Further, the pathway analysis revealed a newlinelarge scale reprogramming of genes involving carbon metabolism (2.5%), plant newlinehormone signaling (1.4%), and glutathione metabolism (0.6%). Moreover, a newlinecomparative account of Cd toxicity revealed a total of 11,294 transcripts to be newlinesignificantly differentially expressed. The genes related to response to chemical, newlineoxidative stress, transport, and secondary metabolism were upregulated whereas newlinemulticellular organismal development, developmental process, photosynthesis were newlinedownregulated by Cd treatment. Furthermore, 616 membrane transport proteins were newlinefound to be significantly differentially expressed. Cd-related transporters such as newlinemetal transporter (Nramp1), metal tolerance protein (MTPC2, MTP11), cadmiumtransporting newlineATPase, and plant cadmium resistance protein (PCR2, PCR6) were newlineupregulated while cadmium/z