Shraboni Ghosh

Bio: Shraboni Ghosh is an academic researcher. The author has contributed to research in topics: Medicine & Arabidopsis. The author has an hindex of 6, co-authored 10 publications receiving 213 citations.

Differentially expressed seed aging responsive heat shock protein OsHSP18.2 implicates in seed vigor, longevity and improves germination and seedling establishment under abiotic stress.

Abstract: Small heat shock proteins (sHSP) are a diverse group of proteins and are highly abundant in plant species. Although majority of these sHSPs were shown to express specifically in seed, their potential function in seed physiology remains to be fully explored. Our proteomic analysis revealed that OsHSP18.2, a class II cytosolic HSP is an aging responsive protein as its abundance significantly increased after artificial aging in rice seeds. OsHSP18.2 transcript was found to markedly increase at the late maturation stage being highly abundant in dry seeds and sharply decreased after germination. Our biochemical study clearly demonstrated that OsHSP18.2 forms homooligomeric complex and is dodecameric in nature and functions as a molecular chaperon. OsHSP18.2 displayed chaperone activity as it was effective in preventing thermal inactivation of Citrate Synthase. Further, to analyze the function of this protein in seed physiology, seed specific Arabidopsis overexpression lines for OsHSP18.2 were generated. Our subsequent functional analysis clearly demonstrated that OsHSP18.2 has ability to improve seed vigor and longevity by reducing deleterious ROS accumulation in seeds. In addition, transformed Arabidopsis seeds displayed better performance in germination and cotyledon emergence under adverse conditions as well. Collectively, our work demonstrates that OsHSP18.2 is an aging responsive protein which functions as a molecular chaperon and possibly protect and stabilize the cellular proteins from irreversible damage particularly during maturation drying, desiccation and aging in seeds by restricting ROS accumulation and thereby improves seed vigor, longevity and seedling establishment.

Differentially expressed galactinol synthase(s) in chickpea are implicated in seed vigor and longevity by limiting the age induced ROS accumulation

Abstract: Galactinol synthase (GolS) catalyzes the first and rate limiting step of Raffinose Family Oligosaccharide (RFO) biosynthetic pathway, which is a highly specialized metabolic event in plants. Increased accumulation of galactinol and RFOs in seeds have been reported in few plant species, however their precise role in seed vigor and longevity remain elusive. In present study, we have shown that galactinol synthase activity as well as galactinol and raffinose content progressively increase as seed development proceeds and become highly abundant in pod and mature dry seeds, which gradually decline as seed germination progresses in chickpea (Cicer arietinum). Furthermore, artificial aging also stimulates galactinol synthase activity and consequent galactinol and raffinose accumulation in seed. Molecular analysis revealed that GolS in chickpea are encoded by two divergent genes (CaGolS1 and CaGolS2) which potentially encode five CaGolS isoforms through alternative splicing. Biochemical analysis showed that only two isoforms (CaGolS1 and CaGolS2) are biochemically active with similar yet distinct biochemical properties. CaGolS1 and CaGolS2 are differentially regulated in different organs, during seed development and germination however exhibit similar subcellular localization. Furthermore, seed-specific overexpression ofCaGolS1 and CaGolS2 in Arabidopsis results improved seed vigor and longevity through limiting the age induced excess ROS and consequent lipid peroxidation.

Rice PROTEIN l-ISOASPARTYL METHYLTRANSFERASE isoforms differentially accumulate during seed maturation to restrict deleterious isoAsp and reactive oxygen species accumulation and are implicated in seed vigor and longevity.

Abstract: PROTEIN l-ISOASPARTYL O-METHYLTRANSFERASE (PIMT) is a protein-repairing enzyme involved in seed vigor and longevity. However, the regulation of PIMT isoforms during seed development and the mechanism of PIMT-mediated improvement of seed vigor and longevity are largely unknown. In this study in rice (Oryza sativa), we demonstrate the dynamics and correlation of isoaspartyl (isoAsp)-repairing demands and PIMT activity, and their implications, during seed development, germination and aging, through biochemical, molecular and genetic studies. Molecular and biochemical analyses revealed that rice possesses various biochemically active and inactive PIMT isoforms. Transcript and western blot analyses clearly showed the seed development stage and tissue-specific accumulation of active isoforms. Immunolocalization studies revealed distinct isoform expression in embryo and aleurone layers. Further analyses of transgenic lines for each OsPIMT isoform revealed a clear role in the restriction of deleterious isoAsp and age-induced reactive oxygen species (ROS) accumulation to improve seed vigor and longevity. Collectively, our data suggest that a PIMT-mediated, protein repair mechanism is initiated during seed development in rice, with each isoform playing a distinct, yet coordinated, role. Our results also raise the intriguing possibility that PIMT repairs antioxidative enzymes and proteins which restrict ROS accumulation, lipid peroxidation, etc. in seed, particularly during aging, thus contributing to seed vigor and longevity.

Design, Synthesis and Anti Colon Cancer Activity Evaluation of Phosphorylated Derivatives of Lamivudine (3TC)

Abstract: The novel phosphorylated derivatives of Lamivudine (5a-5l) as potential anti colon cancer agents are synthe- sized. These title compounds are designed based on the basic pyrimidine derivative lamivudine as a starting compound and reacted with various phosphorodichloridates followed by the introduction of bioactive groups at the phosphorus. Their structures were characterized by IR, 1 H, 13 C, 31 P NMR and mass spectral analyses. All the compounds were evaluated for their anti colon cancer activity against COLO-205 cell lines in vitro studies. Among them 5a and 5b emerged as lead compounds with 0.003 μM and 0.0001 μM values.

Arabidopsis SKP1-like protein13 (ASK13) positively regulates seed germination and seedling growth under abiotic stress.

Abstract: SKP1 (S-phase kinase-associated protein1) proteins are key members of the SCF (SKP-cullin-F-box protein) E3 ligase complexes that ubiquitinate target proteins and play diverse roles in plant biology. However, in comparison with other members of the SCF complex, knowledge of SKP1-like proteins is very limited in plants. In the present work, we report that Arabidopsis SKP1-like protein13 (ASK13) is differentially regulated in different organs during seed development and germination and is up-regulated in response to abiotic stress. Yeast two-hybrid library screening and subsequent assessment of in vivo interactions through bimolecular fluorescence complementation analysis revealed that ASK13 not only interacts with F-box proteins but also with other proteins that are not components of SCF complexes. Biochemical analysis demonstrated that ASK13 not only exists as a monomer but also as a homo-oligomer or heteromer with other ASK proteins. Functional analysis using ASK13 overexpression and knockdown lines showed that ASK13 positively influences seed germination and seedling growth, particularly under abiotic stress. Taken together, our data strongly suggest that apart from participation to form SCF complexes, ASK13 interacts with several other proteins and is implicated in different cellular processes distinct from protein degradation.

Iconography : Seed longevity: Survival and maintenance of high germination ability of dry seeds

Abstract: The seed constitutes the main vector of plant propagation and it is a critical development stage with many specificities. Seed longevity is a major challenge for the conservation of plant biodiversity and for crop success. Seeds possess a wide range of systems (protection, detoxification, repair) allowing them to survive in the dry state and to preserve a high germination ability. Therefore, the seed system provides an appropriate model to study longevity and aging.

Purification of Laboratory Chemicals, Fourth Edition. By W. L. F.

Abstract: Purification of Laboratory Chemicals, Fourth Edition By W L FArmarego (Australian National University, The John Curtin School ofMedical Research) and DD Perrin (Australian National University,Formerly of the Medical Chemistry Group) Butterworth Heinemann Press:Oxford 1996 v + 529 pp ARP $19500 ISBN 0-7506-2839-1

Late seed maturation: drying without dying

Abstract: Besides the deposition of storage reserves, seed maturation is characterized by the acquisition of functional traits including germination, desiccation tolerance, dormancy, and longevity. After seed filling, seed longevity increases up to 30-fold, concomitant with desiccation that brings the embryo to a quiescent state. The period that we define as late maturation phase can represent 10-78% of total seed development time, yet it remains overlooked. Its importance is underscored by the fact that in the seed production chain, the stage of maturity at harvest is the primary factor that influences seed longevity and seedling establishment. This review describes the major events and regulatory pathways underlying the acquisition of seed longevity, focusing on key indicators of maturity such as chlorophyll degradation, accumulation of raffinose family oligosaccharides, late embryogenesis abundant proteins, and heat shock proteins. We discuss how these markers are correlated with or contribute to seed longevity, and highlight questions that merit further attention. We present evidence suggesting that molecular players involved in biotic defence also have a regulatory role in seed longevity. We also explore how the concept of plasticity can help understand the acquisition of longevity.

Plant small heat shock proteins - evolutionary and functional diversity.

Abstract: Small heat shock proteins (sHSPs) are an ubiquitous protein family found in archaea, bacteria and eukaryotes. In plants, as in other organisms, sHSPs are upregulated by stress and are proposed to act as molecular chaperones to protect other proteins from stress-induced damage. sHSPs share an 'α-crystallin domain' with a β-sandwich structure and a diverse N-terminal domain. Although sHSPs are 12-25 kDa polypeptides, most assemble into oligomers with ≥ 12 subunits. Plant sHSPs are particularly diverse and numerous; some species have as many as 40 sHSPs. In angiosperms this diversity comprises ≥ 11 sHSP classes encoding proteins targeted to the cytosol, nucleus, endoplasmic reticulum, chloroplasts, mitochondria and peroxisomes. The sHSPs underwent a lineage-specific gene expansion, diversifying early in land plant evolution, potentially in response to stress in the terrestrial environment, and expanded again in seed plants and again in angiosperms. Understanding the structure and evolution of plant sHSPs has progressed, and a model for their chaperone activity has been proposed. However, how the chaperone model applies to diverse sHSPs and what processes sHSPs protect are far from understood. As more plant genomes and transcriptomes become available, it will be possible to explore theories of the evolutionary pressures driving sHSP diversification.

Transcription factors as key molecular target to strengthen the drought stress tolerance in plants.

Abstract: Amid apprehension of global climate change, crop plants are inevitably confronted with a myriad of abiotic stress factors during their growth that inflicts a serious threat to their development and overall productivity. These abiotic stresses comprise extreme temperature, pH, high saline soil, and drought stress. Among different abiotic stresses, drought is considered the most calamitous stressor with its serious impact on the crops' yield stability. The development of climate-resilient crops that withstands reduced water availability is a major focus of the scientific fraternity to ensure the food security of the sharply increasing population. Numerous studies aim to recognize the key regulators of molecular and biochemical processes associated with drought stress tolerance response. A few potential candidates are now considered as promising targets for crop improvement. Transcription factors act as a key regulatory switch controlling the gene expression of diverse biological processes and, eventually, the metabolic processes. Understanding the role and regulation of the transcription factors will facilitate the crop improvement strategies intending to develop and deliver agronomically-superior crops. Therefore, in this review, we have emphasized the molecular avenues of the transcription factors that can be exploited to engineer drought tolerance potential in crop plants. We have discussed the molecular role of several transcription factors, such as basic leucine zipper (bZIP), dehydration responsive element binding (DREB), DNA binding with one finger (DOF), heat shock factor (HSF), MYB, NAC, TEOSINTE BRANCHED1/CYCLOIDEA/PCF (TCP), and WRKY. We have also highlighted candidate transcription factors that can be used for the development of drought-tolerant crops.