NOPR Collection: Pages 523-590

Allelic variations in dnaK of thermotolerant bacilliinhabiting thermal springs

Tue, 01 Aug 2017 00:00:00 GMT

Title: Allelic variations in dnaK of thermotolerant bacilliinhabiting thermal springs Authors: Kumar, Murugan; Jagannadham, Prashant Tej Kumar; Satheesh, Viswanathan; Prasanna, Radha; Saxena, Anil Kumar Abstract: Abiotic stresses including high or low temperature are known to affect productivity in plants as well as microflora, and often heat shock proteins (Hsps) are induced in cells experiencing such heat stress. Hsp 70 which belongs to one of the five major families of Hsps, DnaK family, plays a vital role in the protection and recovery of cells damaged by heat stress. Further, the role of dnak gene encoding a protein related to Hsp70 in thermoregulation has been established already. In this study, we analyzed a set of thermotolerant bacilli for variation in the dnaK gene that codes for DnaK/Hsp70 protein. A part of the dnaK was amplified from seven different bacilli isolated from Manikaran hot springs, Himachal Pradesh, India. Phylogenetic analyses of dnaK in the set of strains generated four clusters, three representing highly thermotolerant strains and one, a moderately thermotolerant strain. However, analyses of deduced amino acid sequences generated only three clusters, two representing highly thermotolerant strains and one representing moderately thermotolerant strain. Comparison of DnaK of highly thermotolerant strain (M5) and moderately thermotolerant strain (M36) revealed polymorphism for 26 amino acids in the ATPase domain and for one amino acid in the substrate binding domain. It can be hypothesized that polymorphism in the DnaK could be linked to the difference in the temperature tolerance limit of the two strains. Page(s): 527-531

Silencing of fatty acid desaturase (FAD7) gene enhances membrane stability and photosynthetic efficiency under heat stress in tobacco (Nicotiana benthamiana)

Tue, 01 Aug 2017 00:00:00 GMT

Title: Silencing of fatty acid desaturase (FAD7) gene enhances membrane stability and photosynthetic efficiency under heat stress in tobacco (Nicotiana benthamiana) Authors: Hiremath, Sunil S; Sajeevan, RS; Nataraja, Karaba N; Chaturvedi, Ashish K; Chinnusamy, V; Pal, Madan Abstract: Maintenance of cell membrane stability under heat stress is considered as an important adaptive mechanism. In this study, an attempt was made to improve membrane stability under high temperature stress through downregulation of fatty acid desaturase (FAD7) gene by post-transcriptional gene silencing (PTGS) approach using virus-induced gene silencing (VIGS) system in order to decrease trienoic fatty acids. Endogenous FAD7 gene fragment from Nicotiana benthamiana was cloned to construct VIGS vector (pTRV2: FAD7). The Agrobacterium strain harboring the pTRV2: FAD7 was infiltrated into 4-leaf stage N. benthamiana. The downregulation of FAD7 gene in VIGS plants were confirmed through semi quantitative RT-PCR. The FAD7 gene downregulated plants were exposed to normal and 35 and 42ºC temperature stress. In FAD7 silenced plants, the content of linolenic acid (18:3) decreased significantly, while linoleic acid (18:2) increased under high-temperature stress. FAD7 silenced plants showed higher net photosynthetic rate and PS-II efficiency under high-temperature stress as compared to control and empty vector transformed plants. Conversely, lower H₂O₂ content, membrane damage, electrolyte leakage and antioxidative enzyme activities were observed in silenced plants as compared to control. The FAD7 silenced plants exhibited better tolerance to high temperature than wild type due to higher dienoic to trienoic fatty acids ratio imparting membrane stability. The study concludes that alteration in fatty acid composition in thylakoid membranes can lower oxidative stress, improve photosynthetic rate, PS-II efficiency in plants under high temperature stress. Page(s): 532-541

Pattern of salt accumulation and its impact on salinity tolerance in two halophyte grasses in extreme saline desert in India

Tue, 01 Aug 2017 00:00:00 GMT

Title: Pattern of salt accumulation and its impact on salinity tolerance in two halophyte grasses in extreme saline desert in India Authors: Mangalassery, Shamsudheen; Dayal, Devi; Kumar, Arvind; Bhatt, Karan; Nakar, Rupesh; Kumar, Ashwani; Singh, JP; Misra, Arun Kumar Abstract: Halophytes growing in natural saline desert environment survive high levels of salinity adopting suitable mechanisms. Scientific information on such survival mechanisms can be useful in devising management options for extreme saline soils. A field survey on two major halophytes [Aeluropus lagopoides (Linn.) Trin. Ex Thw. and Sporobolus marginatus Hochst. ex A. Rich.] was carried out in the saline desert of Northwest India, Great Rann of Kachchh, to study the pattern of ion accumulation under natural conditions and to assess survival mechanisms of these halophytes. Studied areas in Great Rann had electrical conductivity (EC) values ranging 0.15-83.1 dSm^-1. Occurrence of Sporobolus was observed at sites having salinity as high as 83.06 dSm^-1 and Aeluropus up to 22.7 dSm^-1. Greater accumulation of Na⁺ and Cl^- ions were observed in the roots of these halophytes indicating its restricted uptake by them. There was selective absorption of K⁺, Ca²⁺ and SO₄²⁺ in the leaves of Aeluropus and K⁺, Ca²⁺, Mg²⁺ and SO₄^2- in Sporobolus. With increase in soil salinity, the uptake of Na⁺, K⁺ and SO₄^2- were reduced in Aeluropus whereas the uptake of Na⁺, K⁺ and Cl^- was increased in Sporobolus. Possible mechanisms of salt tolerance of these halophytes are also discussed. Page(s): 542-548

Development of real time PCR assay for detection and quantification of teliospores of Tilletia indica in soil

Tue, 01 Aug 2017 00:00:00 GMT

Title: Development of real time PCR assay for detection and quantification of teliospores of Tilletia indica in soil Authors: Gurjar, Malkhan Singh; Aggarwal, Rashmi; Jogawat, Abhimanyu; Sharma, Sapna; Kulshreshtha, Deepika; Gupta, Anuja; Gogoi, Robin; Thirumalaisamy, PP; Saini, Abhinav Abstract: Tilletia indica, commonly called Karnal bunt, is an internationally quarantined wheat fungal pathogen which affects commercial seed trading as well as the quality of wheat grain for consumption. The teliospores of Tilletia indica surviving in soil serve as the primary source of inoculum and play a major role in disease development. Proper identification and detection of T. indica teliospores based on morphological features and germination of teliospores is time consuming and tedious. In this study, we validated PCR based species-specific primer which amplified 570 bp fragments using ITSKB primers. Further, the real time PCR assay was developed and standardized for detection and quantification of teliospores in soil. The (R²) correlation coefficient (0.994) between C_T values and DNA concentrations showed the accuracy of qPCR based quantification. The sensitivity of qPCR marker was 100 fg. Thirteen field soil samples were assessed by qPCR for quantification of teliospore DNA. Low fungal DNA (15135.61 fg) was detected in field soil (K10) from Karnal, Haryana, India while high DNA concentration (3.31 ng) was detected in field soil from IARI, New Delhi (K4). The qPCR assay was done to correlate DNA concentration and number of teliospores per gram soil. The 125.89 fg DNA concentration of T. indica detected corresponding limit of 14 teliospores. Minimum detection limit in terms of teliospores count was 14. The teliospores recovered from Karnal and IARI farm soils by centrifugation method were 450 and 1341, respectively while the qPCR assay based analysis detected higher number of teliospores ranging 1762 to 368332 teliospores. Thus, the developed qPCR diagnostic marker could be used for accurate, reliable and rapid detection of teliospores in soil which would further help in monitoring, quantifying teliosporic load and threshold level of inoculum in soil. Page(s): 549-554