Department of Life Sciences

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Browsing Department of Life Sciences by Author "Das, Malay"

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    Characterization of the Bambusa tulda Roxb inflorescences and flowers at the morphological anatomical and genetic levels to understand floral organ developments and differentiation in bamboo
    Das, Malay
    Bamboos belong to the monocotyledonous plant family Poaceae and subfamily Bambusoideae. Bamboos represent an extreme example of perennialism, where the reproductive phase begins after completion of an extended vegetative phase, which may vary across species. Other than delayed flowering time, existence of two different types of inflorescences, genetics of floral development and nature of pollen compatibility make bamboo unique in comparison to other grasses. The main aim of this study was to understand the floral organ development and pollination mechanism in Bambusa tulda. In this study, the relative abundance of two different types of inflorescence in an entire flowering cycle were analysed and rate of seed setting was compared. One potential limitation to perform gene expression analyses on Bambusa members was the absence of suitable reference genes to normalize expression data. In this study, reference genes were identified, which were stable across species, organs and developmental stages. In order to understand the molecular mechanism that regulates flower development, the floral meristem identity genes MADS14, MADS15 and MADS18 were sequenced from B. tulda and their expression pattern was analyzed across different vegetative and reproductive tissues. In order to understand the genetics of pollen compatibility in bamboo, in vivo pollination experiments were performed. The finding indicated that B. tulda is primarily a cross pollinated species. In order to further understand the molecular mechanism regulating genetic compatibility in bamboo, selected members of RNase T2 and Fbox gene families were studied. Overall, the findings of this study will be useful to understand the morphological, ecological and molecular basis of flower development and genetic compatibility in bamboos.
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    Comprehensive morphological and molecular analyses of flowering events in Bambusa tulda
    Das, Malay
    Flowering is one of the most important adaptations in the history of plant evolution. Our current understanding of flowering and the genes involved in the regulation of flowering time are based on the studies conducted on the model plants Arabidopsis thaliana and Oryza sativa. Since both these plants are annual and herbaceous, it is unlikely that the information obtained from these studies can directly be translated to explain the unusually extended flowering time in bamboo. The ecological impacts caused due to bamboo flowering are known for decades, but our knowledge about flower development and also the genes controlling such unique flowering behaviour is very inadequate in bamboo. a major objective of this study was to understand the detailed reproductive features of B. tulda Roxb. by studying the morphological (inflorescence, flower and pollen), histological (inflorescence) and biochemical (pollen viability) analyses. This study observed that protrandry, limited pollen liberation, low pollen viability and low seed setting are prevalent in B. tulda. Another major objective of this study was to characterize important flower induction and pathway integrator genes in order to understand their role in flower induction in tropical bamboos. Four copies of FLOWERING LOCUS T (BtFT1, BtFT2, BtFT3 and BtFT4) and two copies of FD (BtFD1, BtFD2) genes were identified and their tissue-specific as well as diurnal gene expression analyses revealed possible functional divergence among the closely related homologs. Taken together, this study indicates that copy number expansion and expression divergence may lead to new regulation of flowering gene functions in bamboo.
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    Identification and molecular characterization of important flowering genes in Bambusa tulda Roxb with major emphasis on photoperiodic pathway and integrator genes
    Das, Malay
    Bamboos belong to the subfamily Bambusoideae, family Poaceae and are phylogenetically close to the reference monocot rice (O. sativa). They display extensive variations with respect to flowering time, which may extend upto 120 years. Besides, another ecological feature is mass death of all the flowering culms, known as semelparity. Therefore, it has direct impact on forest dynamics and indirect impact on the sustainability of crops. Flower induction is a very important developmental events in plants' life. It takes place in a favorable environment as a result of regulatory crosstalk at the molecular level. Signals from multiple external and internal sources ger synchronized to decide the timing of flowering. The two major environmental stimuli that influence flowering are light and temperature. In particular, duration and nature of light plays very important role, based on which plants can be characterized as long day, short day and day neutral plants. The main focus of this study is to understand the role of light mediated flowering pathway on bamboo flowering. Therefore, in this study, four circadian clock genes (LHY, TOCI, ZTL, GI) and two clock integrators (CO A. B) of photoperiodic pathway were identified from Bambusa tulda and sequence characterized in comparison to homologous genes. Detailed studies on expression patterns in different tissues, seasons and diurnal conditions provide important clues regarding their possible involvement in flowering. Finally, in planta overexpression analyses of BFD1 and BFD2 genes in Arabidopsis combined with bioinformatics analyses demonstrated that the two genes perform diverse developmental roles in bamboo.
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    Screening of bamboo species available in West Bengal, India to assess their utility as lignocellulosic biomass resources
    Das, Malay
    Bamboos, a category of non-timber grasses, belong to the family Poaceae and the subfamily Bambusoideae. Therefore, phylogenetically they are close to rice (Oryza sativa), Brachypodium and other reference grasses. It has immense potential for the ligno-cellulose biomass (LCB) based biofuel industry primarily due to their high growth rate, which leads to rapid accumulation of LCBs, high fibre contents, requirement of less agronomic input, existence of a wide genetic pool, and having no conflict with food crops. Despite this, there haven't been sufficient investigations to study the biology of cellulose and lignin deposition in tree bamboos. There remains a serious dearth of understanding, in particular, with respect to varying cellulose and lignin levels that exist at the germplasm/population level. Therefore, in this study, seven abundantly growing and widely distributed bamboo species of West Bengal, India, namely Bambusa balcooa, B. tulda, B. bambos, B. nutans, B. striata, Dendrocalamus giganteus, and D. strictus were investigated to assess their potential as LCB donors. In order to determine the chemical composition of LCBs obtained from the internode tissues of these species, this study utilized physico-chemical techniques such as, Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) Spectroscopy, Thermal Gravimetric Analysis (TGA), X-ray diffraction (XRD), biochemical assessments of α-cellulose, lignin levels and important anatomical features with major emphasis on the vascular bundles. Findings of this study indicated that analysing intensity of stain specific for cellulose and lignin could be a useful, yet cheap marker to screen a big collection of bamboo species and germplasms in order to identify superior species/genotype having potential for the liquid, biofuel industry. Collective analysis of all these parameters have identified B. bambos as the reference bamboo species having enormous prospects for future biomass based bioenergy production. . Also, in this study, three Cellulose Synthesis A (CesA) genes possibly associated with secondary cell wall formation had been identified and sequence characterized from the tropical bamboo B. tulda. Expression characterization from selected, vegetative tissues and developmental tissue stages indicate that they might be good candidate for future investigation to obtain bio stock having enhanced biomass accumulation. Collectively, this study developed an integrated strategy that might be utilized in future on other plants having similar biomass based bioenergy potential.