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Advisor: Aruna Tyagi
Title: Targeted Transcriptomic and Metabolic Profiling of Abscisic Acid Biosynthetic Pathway in Rice for Drought Tolerance
Language: en_US
Type: Thesis
Agrotags: null
Keywords: Rice, Drought, Abscisic acid, NCED, ZEP
Abstract: Rice is a major staple food crop for more than 60 % of the world’s population. Drought limits the production of rice worldwide. Abscisic acid (ABA) is a plant stress hormone which plays versatile roles under different environmental stresses. Though the relationship between drought stress and ABA accumulation is well established in many crops, the impact of drought on candidate genes and intermediates of ABA biosynthesis pathway has not been well defined. This study was focused to establish the impact of drought stress on various intermediates namely beta-carotene, zeaxanthin, antheraxanthin, violaxanthin, neoxanthin, and candidate genes viz. zeaxanthin epoxidase (ZEP) and 9-cis epoxycarotenoid dioxygenase (NCED) of ABA biosynthesis pathway in drought tolerant (N22) and susceptible (IR64) cultivars of rice at anthesis stage (65 DAT) at different stress levels. In stressed plants, zeaxanthin significantly increased (92 %), while concentration of beta-carotene, antheraxanthin, violaxanthin, neoxanthin metabolites decreased as drought stress progressed. The ZEP expression was upregulated in roots (8.24-fold) and during WDS and didn’t show any change in in leaves. Among five NCED isoforms, NCED3 showed significant upregulation (7.29- fold) in both leaf and root tissue. NCED1 was significantly downregulated (100 %) as stress progressed and was negatively correlated with ABA accumulation. NCED2, NCED4 and NCED5 didn’t show any significant change in their expression pattern. In the present study, the complete NCED1 gene of 1917 bp was cloned and characterized from rice (Oryza sativa L. cv. N22) as no earlier reports were available for its characterization from the indica cultivar. The phylogenic tree showed that NCED1 of japonica rice and NCED1 of indica rice were in the same group. The NCED1 had no intron and encoded a protein of 639 amino acids with a predicted molecular mass of 68.62 kD and pI of 6.07. The results of this study indicate that drought stress has significant impact on the expression of candidate genes and concentration of metabolites of ABA biosynthesis pathway. There was significantly higher accumulation of ABA, a stress hormone, in N22 leaves (47 %) and roots (29.89 %) as compared to IR64. There was very low concentration of metabolites observed in roots as compared to leaves in both genotypes. The drought tolerant N22 genotype had significant higher concentration of intermediates and higher expression of ZEP and NCED3 genes which might provide ability of drought tolerance as compared to IR64. Also, genotypes with higher metabolites have higher drought tolerance, so we can use these genotypes for drought tolerant breeding program. This will definitely help to devise strategies for manipulation of ABA levels for imparting stress tolerance study in rice as well as other crops.
Description: T-10081
Subject: Biochemistry
Theme: Targeted Transcriptomic and Metabolic Profiling of Abscisic Acid Biosynthetic Pathway in Rice for Drought Tolerance
These Type: Ph.D
Issue Date: 2019
Appears in Collections:Theses

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