Browsing by Author "Bhagavatula, Vani"

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Alteration in chloroplast structure and thylakoid membrane composition due to in vivo heat treatment of rice seedlings: correlation with the functional changes
(Elsiever, 2001) Bhagavatula, Vani
Exposure of 25 °C-grown, seven-day-old rice seedlings to mild heat stress of 40 °C for 24 h in dark did not cause any change in protein or pigment content of the thylakoids, but produced major disorganization of chloroplast ultrastructure. This heat induced disorganization of thylakoid structure/organization caused significant (∼65 percnt;) loss in PSII activity, slight loss in PSI activity, and brought about a decrease in relative quantum efficiency of PSII. The herbicide 14C atrazine binding assay revealed a decreased number of binding sites of the herbicide and altered the herbicide dissociation constant, suggesting that the heat induced disorganization of the thylakoids affects the acceptor side of PSII. Cation induced Chla fluorescence analyses at room temperature and low temperature indicated thatin vivo heat exposure of rice seedlings altered the extent of energy transfer in favor of PSI
Alteration in NAD+/NADH ratio regulates salt stress induced proline accumulation in Vigna radiata.
(NAS, 1996) Bhagavatula, Vani
Five-day-old vigna radiata seedlings exposed to NaCI stress induced a significant enhancement in proline levels accompanied by reduction in growth
Analysis of seven putative Na+/H+ antiporters of Arthrospira platensis NIES-39 using transcription profiling and in silico studies: an indication towards alkaline pH acclimation
(Springer, 2019-09) Chowdhury, Shibasish; Bhagavatula, Vani
Na+/H+ antiporters mediated pH regulation is one of the known mechanism(s), which advocates a possible role of the antiporters in the alkaline pH tolerance of Arthrospira platensis NIES-39. Seven putative Na+/H+ antiporters have been reported in A. platensis NIES-39. Based upon the in silico analysis, the seven putative antiporters were characterized into two different superfamilies, where A1, Q2, L2, and L6 belonged to the CPA1 family whereas C5, D5 and O6 belonged to CPA2 family. The orientation of functionally important residues in both CPA1 and CPA2 subfamily are conserved in modeled Q2 and C5 antiporters. Conserved domain analysis of the seven putative antiporters indicated the presence of nine different kinds of domains. Out of these nine domains, six domains function as monovalent cation-proton antiporters and two as the universal stress protein (Usp) category. Transcription profile of these seven antiporters was also generated at three different pH (7, 9 and 11) and time frames which showed a significant difference in the mRNA levels along with a temporal pattern of the expression profile. The in silico and the real-time PCR analysis put together, suggest the active participation of these seven putative Na+/H+ antiporters in alkaline pH homeostasis of this cyanobacterial strain where CPA1 subfamily antiporters play a major role.
Analysis of seven putative Na+/H+ antiporters of Arthrospira platensis NIES-39 using transcription profiling and in silico studies: an indication towards alkaline pH acclimation
(Springer, 2019-09) Bhagavatula, Vani; Chowdhury, Shibasish
Na+/H+ antiporters mediated pH regulation is one of the known mechanism(s), which advocates a possible role of the antiporters in the alkaline pH tolerance of Arthrospira platensis NIES-39. Seven putative Na+/H+ antiporters have been reported in A. platensis NIES-39. Based upon the in silico analysis, the seven putative antiporters were characterized into two different superfamilies, where A1, Q2, L2, and L6 belonged to the CPA1 family whereas C5, D5 and O6 belonged to CPA2 family. The orientation of functionally important residues in both CPA1 and CPA2 subfamily are conserved in modeled Q2 and C5 antiporters. Conserved domain analysis of the seven putative antiporters indicated the presence of nine different kinds of domains. Out of these nine domains, six domains function as monovalent cation-proton antiporters and two as the universal stress protein (Usp) category. Transcription profile of these seven antiporters was also generated at three different pH (7, 9 and 11) and time frames which showed a significant difference in the mRNA levels along with a temporal pattern of the expression profile. The in silico and the real-time PCR analysis put together, suggest the active participation of these seven putative Na+/H+ antiporters in alkaline pH homeostasis of this cyanobacterial strain where CPA1 subfamily antiporters play a major role.
Characterization of high temperature induced stress impairments in thylakoids of rice seedlings
(NISCAIR, 2001-08) Bhagavatula, Vani
Exposure o f isolated thylakoids or intact plants to elevated temperature is known to inhibit photosynthesis at multiple sites. We have investigated the effect of elevated temperature (40°C) for 24 hr in dark on rice seedlings to characterize the extent of damage by inl vivo heat stress on photofunctions of photosystem II (PSII). Chi a fluorescence transient analysis in the intactrice leaves indicated a loss in PSII photochemistry (Fv) and an associated loss in the number of functional PSII units. Thylakoids isolated from rice seedlings exposed to mild heat stress exhibited > 50% reduction in PSII catalyzed oxygen evolution activity compared to the corresponding control thylakoids. The ability of thy lakoid membranes from heat exposed seed lings to photooxidize artificial PSII electron donor, DPC, subsequent to washing the thylakoids with alkaline Tris or NH2OH was also reduced by ~40% compared to control Tris or NH2OH washed thylakoids. This clearly indicated that besides the disruption of oxygen evolving complex (OEC) by 40°C heat exposure for 24 hr, the PSII reaction centers were impaired by inl vivo heat stress. The analysis of Mn and manganese stabilizing protein (MSP) contents showed no breakdown of 33 kDa extrinsic MSP and only a marginal loss in Mn. Thus, we suggest that the extent of heat induced loss of OEC must be due to disorganization of the OEC complex by in vivo heat stress. Studies with inhibitors like DCMU and atrazine clearly indicated that in vivo heat stress altered the acceptor side significantly. [14C] Atrazine binding studies clearly demonstrated that there is a significant alteration in the QB binding site on D1 as well as altered QA to QB equilibrium. Thus, our results show that the loss in PSII photochemistry by in vivo heat exposure not only alters the donor side but significantly alters the acceptor side of PSII .
Differential response of photosynthetic apparatus towards alkaline pH treatment in NIES-39 and PCC 7345 strains of Arthrospira platensis
(Springer, 2021-05) Chowdhury, Shibasish; Bhagavatula, Vani
Alkaline stress is one of the severe abiotic stresses, which is not well studied so far, especially among cyanobacteria. To affirm the characteristics of alkaline stress and the subsequent adaptive responses in Arthrospira platensis NIES-39 and Arthrospira platensis PCC 7345, photosynthetic pigments, spectral properties of thylakoids, PSII and PSI activities, and pigment-protein profiles of thylakoids under different pH regimes were examined. The accessory pigments showed a pH-mediated sensitivity. The pigment-protein complexes of thylakoids are also affected, resulting in the altered fluorescence emission profile. At pH 11, a possible shift of the PBsome antenna complex from PSII to PSI is observed. PSII reaction center is found to be more susceptible to alkaline stress in comparison to the PSI. In Arthrospira platensis NIES-39 at pH 11, a drop of 68% in the oxygen evolution with a significant increase of PSI activity by 114% is recorded within 24 h of pH treatment. Alterations in the cellular ultrastructure of Arthrospira platensis NIES-39 at pH 11 were observed, along with the increased number of plastoglobules attached with the thylakoid membranes. Arthrospira platensis NIES-39 is more adaptable to pH variation than Arthrospira platensis PCC 7345.
Differential sensitivities of photofunctions of thylakoid membranes to in vivo elevated temperature stress in Oryza sativa (var. Kalinga III) seedlings
(Springer, 1999) Bhagavatula, Vani
Effect of nitrate availability on expression of multi sensor histidine kinase gene in Spirulina platensis PCC 7345
(Springer, 2011) Bhagavatula, Vani
Addition of nitrate (NO −3 ) to a suspension of NO −3 -depleted Spirulina platensis PCC 7345 restored back the PSII reaction centre efficiency. Using RAPD/RT-PCR differential display, we have detected the upregulation of a novel gene in filaments starved of nitrogen when enriched with NO −3 . Semiquantitative RT-PCR clearly shows that NO −3 repletion induces the expression of this gene. Its nucleotide sequence is homologous to multi sensor histidine kinase (hstk) from Spirulina platensis NIES-39 and Spirulina maxima CS-328 genes. The open reading frame of this gene encodes a protein of 98 amino acids contains sensory domain of PAS domain.
Effect of short-term heat treatment of rice seedlings on sensitivity of thylakoid membranes to photoinhibition
(Springer, 1996) Bhagavatula, Vani
The after-effects of 24 h high temperature (35 or 45 ~ treatment on the photochemical activities and photooxidative lipid peroxidation, subsequent to their irradiation were studied in 7-d-old etiolated rice (Oryza sativa) seedlings. Photosystem (PS) 1 and PS 2 mediated photoreactions of thylakoids isolated from the seedlings exposed to high temperature did not differ significantly from the thylakoids isolated from control seedlings (25 ~ Hence, all kinds of tested thylakoids were equally efficient in capturing and utilizing radiant energy. The high irradiance induced loss in PS 2 activity and lipid peroxidation measured in terms of malondialdehyde production was more rapid in thylakoids isolated from stressed seedlings as compared to that of control seedlings. Thus the thylakoids isolated from the stressed seedlings were more prone to photodamage than those from the control seedlings.
Elevated Temperature Treatment Induced Alteration in Thylakoid Membrane Organization and Energy Distribution between the Two Photosystems in Pisum sativum
(Degruyter, 2014) Bhagavatula, Vani
High temperature causes changes in the struc-tural organization of thylakoid membranes affect-ing excitation energy distribution as the well asrates of photochemical reactions. Thus, high tem-perature causes alterations not only in the physi-ochemical properties but also the functional or-ganization of the thylakoid membranes (Pastenesand Horton, 1996). Heat stress has been reportedto affect various photosynthetic processes includ-ing electron flow on the donor side of PSII (Nashet al., 1985; Enamiet al., 1994) and at the acceptorside of PSII (Bukhovet al., 1990; Cao and Govind-jee, 1990), inactivation of enzymes like ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco) andferredoxin-NADP reductase (FNR),
Handheld, smartphone based spectrometer for rapid and nondestructive testing of citrus cultivars
(Springer, 2020-10-14) Bhagavatula, Vani
Optimum maturity and ripeness at the time of harvest is highly important to maintain the nutritional parameters of fruits. Maturity and ripeness of most of the fruit samples depends on various physiochemical parameters such as color, shape, size, total soluble solid and many more. Several state-of-the-art solutions such as GC–MS, Electronic Nose, Spectrometer and many more are available to measure various fruit quality parameters but most of the solutions available in the market are bulky, time consuming, lab-level and requires skilled manpower for operation. Presented manuscript reports a battery operated, smartphone spectrometer based solution to carry out the variety of activities in the field. Overall device uses UV–Vis-NIR led array as source and collection of spectral sensors (AS7262 and OPT101) to acquire overall UV–Vis-NIR spectrum over the range of 400–1000 nm with the resolution of 40 nm. Designed source and detector modules have been interfaced with designed triggering, filter and amplification circuit. A low power wireless solution along with on-board microcontroller facility has been designed and interfaced with circuits, source and detectors. All essential components such as source, detectors, filters, lens and all circuits have been assembled in a housing of dimensions 18.0 × 9.0 × 6.0 (in cm) and the entire device weighs 183.35 g. Different statistical and neural network based modelling techniques have been explored to design prediction models for total soluble solids, weight, volume, chlorophyll, sugar content and acidity. Models have been evaluated based on accuracy, memory and time usage. Best performed models have been used to train handheld smartphone based spectrometer device to predict various quality parameters for citrus samples. System communicates data to smartphone based android app to display various parameters. Android app also provides facility to save data on cloud with tree and orchard ID to monitor overall yield and harvesting time.
Heat stress on rice leaves probed by the fluorescence transient OKJIP.
(Springer, 1999) Bhagavatula, Vani
Inhibition of mitochondrial electron transport is the prime cause behind proline accumulation during mineral deficiency in Oryza sativa
(Springer, 1993) Bhagavatula, Vani
The concentration of proline in shoots of rice (Oryza sativa) seedlings raised in distilled water was about 3.3 times higher than in the seedlings raised in modified B5 medium. The shoots of seedlings raised in B5 medium which was depleted of calcium, iron, magnesium or potassium had a higher concentration of proline than those grown in standard B5 medium. The shoots of seedlings raised in distilled water with iron had a lower level of proline than those in distilled water. These results suggest that iron deficiency leads to high proline accumulation.
Interplay between calcium influx and nitrate assimilation in Spirulina platensis
(Academic Journals, 2011) Bhagavatula, Vani
Nitrate assimilation and its interplay with Ca2+ ion transport has been studied in Spirulina platensis PCC 7345, an alkaliphilic filamentous cyanobacterium. We have used verapamil, a calcium-channel blocker and sodium orthovanadate, a calcium efflux blocker, to study the effect of nitrate assimilatory setup. Nitrate uptake (NU) increased significantly with verapamil but was inhibited by sodium orthovanadate. Nitrate reductase and nitrite reductase activities were stimulated with verapamil as well as sodium orthovanadate. Glutamine synthetase activity was not significantly altered by both the inhibitors. Our results suggest that the steady state levels of NU, NR and NiR activities are inter linked with Ca2+ influx into the cells from the external medium.
Lipase Immobilization Techniques for Biodiesel Production: An Overview
(IBIMA, 2014-05-13) Bhagavatula, Vani; Mehrotra, Rajesh; Mehrotra, Sandhya
The growing energy needs and depleting fuel sources compel us to look towards production of biodiesel, an appropriate alternative. The industrially used chemical catalysis process is beset with problems that enzymatic production using lipases could avoid. In this light, the immobilization of lipases plays an important role in the optimization of the production process. This review discusses the various techniques that have been studied for lipase immobilization, namely adsorption, covalent attachment, entrapment, cross-linked enzyme agglomerates and whole-cell biocatalysts, while highlighting their benefits and drawbacks. It also sheds light on the future of enzyme immobilization and its industrial application.
Machine-vision based handheld embedded system to extract quality parameters of citrus cultivars
(USDA, 2020) Bhagavatula, Vani
This manuscript introduces a handheld machine vision based system design that is capable of standalone operation using touch screen based user interface and also can operate through smartphone based android app. System uses 8.0 Megapixel, 1080p CMOS camera interfaced with quad-core ARM Cortex-A53 processor based computing platform (Raspberry Pi computing platform) for real time image acquisition and processing. Multi-spectral led array has been used to compensate the effect of external illumination and also to increase the accuracy of measurement. System stores acquired images on interfaced 16.0 G.B. external memory card with date and time information. Various segmentation methods have been explored to extract region of interest in acquired images and compared based on the capability of segmentation in real-time. Segmented images have been used to extract different features such as color, shape, size and texture using various image processing algorithms. Extracted features have been fused together and undergone through different statistical and neural network based modelling methods to correlate features dataset generated using handheld system with standard quality parameters of collected citrus samples. Performance of the established correlation models for various quality parameters such as chlorophyll, sugar content, TSS, weight, pH and volume have been evaluated and best performed models for each quality parameter has been used to train the developed handheld machine vision based system. Overall system is battery operated and also enables cloud connectivity using on-board Wi-Fi facility or smartphone based android app. Overall device has dimensions of 12.0 × 6.0 × 4.0 (in cm), weighs 139.07 g and runs with 5-V rechargeable battery.
Nitrogen acquisition in cyanobacteria
(LAMBERT Academic Publishing, 2011) Bhagavatula, Vani
The Role of Cyanobacteria in Agriculture
(Krishi Sanskriti Publications, 2015) Bhagavatula, Vani; Chowdhury, Shibasish
Microorganisms offer a pool of properties which could be utilized for the benefit of the ecosystem and mankind. They have always played the central role in evolution and shaped out the existing life on earth. The population increase needs to keep pace with the agricultural front to meet the demands with supply. As the crops and other plants are sessile they have to combat biotic and abiotic stresses. The stressful environmental conditions including the stress, soil fertility issues, presence of pathogens etc. can hamper the growth and development of the plants and affect the crop productivity. These conditions could be regulated by using fertilizers specially biofertilizers, as the chemical fertilizers are effective but have deleterious effects on the ecosystem. This article focuses the role of cyanobacteria in agriculture to improve the crop yield. These photosynthetic prokaryotes fix the atmospheric nitrogen into utilizable form and make it available to the plants. They also form symbiotic associations and provide nourishment to the host and in turn get housing either endophytic or exophytic. The growth enhancement was observed when cyanobacteria were inoculated in the fields. This effect was due to hormones like cytokinin, gibberellins and auxin which accelerated growth. Elicitor molecules from these organisms like certain peptides, vitamins, carbohydrates are reported to induce pathogenesis in plants. The exo-polysaccharide of cyanobacteria improves the soil quality and fertility. The recent trend involves the manipulation of the higher plants with the genes from these organisms to improve their production and stress related properties.
Structure-function correlation during the etioplast-chloroplast transition in cucumber cotyledonary leaves
(IJPR, 1998) Bhagavatula, Vani
We studied the development of chloroplasts from etioplasts in the cotyledonary leaves of 4-d-old dark-grown cucumber (Cucumis sativus) seedlings after irradiation (20 μmol m-2 s-1). Upon irradiation, the triggering of chlorophyll (Chl) synthesis and accumulation showed a relatively short lag phase. The irradiation of etiolated seedlings initiated the synthesis of apoproteins of pigment-protein complexes. While Chl-protein 2 (CP2) was detected at 6 h after irradiation, CP1 only after 29 h. The appearance and accumulation of some of the apoproteins were monitored by Western-blotting. LHC2 apoprotein was detected after a 6 h-irradiation. The amounts of D1 protein of photosystem (PS) 2 and PsaA/B protein of PS1 were quantitated by ELISA. Further, the thylakoid membrane function during this time period in terms of PS1- and PS2-mediated electron transfer activity and intersystem electron pool size were analyzed. While PS1 activity was detected after 4 h, PS2-mediated O2 evolution was detected only after a 17 h-irradiation. Fv/Fm value of Chl a fluorescence measurements indicated that the photochemical efficiency of these leaves reached its maximum after 29 h of irradiation. The intersystem pool size of cotyledonary leaves was equivalent to that of the control cotyledonary leaves grown for 25 h under continuous irradiation. Thus etioplasts develop into fully functional chloroplasts after approximately 25 h when 4 d-dark grown cucumber seedlings are continuously moderately irradiated. The development of photosynthetic electron transport chain seems to be limited in time at the level of PS2, possibly at the donor side.