Publications of NIPGR Scientists

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Author: search.filters.author.Tripathi, Bhumi Nath

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    The lld mutation in Pisum sativum used as a genetic tool to discern the plant leaflet/leaf developmental process
    (NISCAIR-CSIR, India, 2013) Sharma, Vishakha; Tripathi, Bhumi Nath; Kumar, Sushil
    Leaves of P. sativum the double mutant genotype tendril-less (tl) leaflet-development (lld), due to the action of lld mutation, produce many leaflets that are aborted at different stages of development. Morphological, vein pattern and histological observations showed that aborted leaflets became cup/bell/trumpet (cup) shaped because of segmental differentiation in the leaflet primordium. Cup's inside lamina surface was adaxial and outer surfaces of cup and its stem were abaxial. The lld cups were phenotypically homologous to aborted leaves described in Arabidopsis thaliana mutants, angustifolia and those which underexpressed the HD-ZIP III proteins. Leaflet primordium was found to grow and establish three dimensional polarities apex-downwards. Primordium produced lateral outgrowth on one side of midvein. Differentiation, in the outgrowth of secondary veins, whose xylem tissues faced each other, established the adaxial-abaxial polarity. Lateral outgrowth then developed a cavity which got bounded by future adaxial epidermis. Further growth, veinlet formation, differentiation of palisade parenchyma and spongy parenchyma followed. Opening of lateral outgrowth at its outer midline produced a flat leaflet with lateral lamina spans. The structural and functional correspondence between leaflet and simple leaves suggested commonality between leaf and leaflet development mechanisms. A molecular model for the lld led leaflet abortion was also provided.
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    Pisum sativum wild-type and mutant stipules and those induced by an auxin transport inhibitor demonstrate the entire diversity of laminated stipules observed in angiosperms
    (Springer, 2013) Kumar, Arvind; Sharma, Vishakha; Khan, Moinuddin; Tripathi, Bhumi Nath; Kumar, Sushil
    About a quarter of angiosperm species are stipulate. They produce stipule pairs at stem nodes in association with leaves. Stipule morphology is treated as a species-specific characteristic. Many species bear stipules as laminated organs in a variety of configurations, including laterally free large foliaceous, small, or wholly leaf-like stipules, and as fused intrapetiolar, opposite, ochreate or interpetiolar stipules. In Pisum sativum, the wild-type and stipule-reduced and cochleata mutants are known to form free large, small, and leaf-like stipules, respectively. Auxin controls initiation and development of plant organs and perturbations in its availability and distribution in the meristems, caused by auxin transport inhibitor(s) (ATIs), lead to aberrations in leaf development. The effect(s) of ATI(s) on stipule development are unexplored. To study the effect of the ATI 1-N-naphthylphthalamic acid (NPA) on stipule morphogenesis, P. sativum explants were grown in vitro in presence of a sublethal concentration of NPA. The NPA-treated shoots produced fused stipules of all the different types described in angiosperms. The observations indicate that (a) the gene sets for stipule differentiation may be common in angiosperms and (b) the interspecies stipule architectural differences are due to mutations, affecting gene expression or activity that got selected in the course of evolution.
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    Transcript profiling identifies novel transcripts with unknown functions as primary response components to osmotic stress in wheat (Triticum aestivum L.)
    (Springer, 2013) Garg, Bharti; Puranik, Swati; Misra, Shrilekha; Tripathi, Bhumi Nath; Prasad, Manoj
    Osmotic stress induced by dehydration and salinity, is among the major abiotic stresses that adversely impacts crop productivity and plants often display cultivar-dependent response against osmotic imbalance. To better understand the molecular mechanisms underlying differential responses to dehydration, transcriptome changes of two contrasting wheat (Triticum aestivum L.) cultivars were evaluated in plants grown under unfavorable osmotic conditions. A total of 107 non-redundant transcripts were identified. Of these, most had unknown functions (31; ~30 %) signifying the existence of putative stress-specific genes in wheat, reported here for the first time. Upon comparing with previous transcriptomic studies, 43 (40 %) of the osmotically-responsive transcripts were found not to be documented. These new transcripts may therefore signify unexplored gene sources for specific responses towards short-term osmotic stress in wheat. Through macroarray analysis, 69 (~64 %) transcripts were found to be differentially expressed (≥3-fold) and expression of 14 transcripts (with known or unknown functions) was further confirmed by quantitative real time PCR. Expression analysis of the seven unknown transcripts also revealed their tissue- and stress-specific regulation. Comparative in silico mapping of these 107 wheat transcripts against available mapping data for rice (40; ~37 %), maize (34; ~32 %), and sorghum (33; ~31 %) revealed presence of wheat orthologous sequences in these cereal crops. This study provides an interesting account on several novel genes, besides those with known functions, which may regulate stress response dynamics and thus, may be used as potential candidates to improve stress adaptability through genetic and molecular studies.
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    Organ-wise homologies of stipule, leaf and inflorescence between Pisum sativum genetic variants, Delonix regia and Caesalpinia bonduc indicate parallel evolution of morphogenetic regulation
    (Springer, 2012) Sharma, Vishakha; Tripathi, Bhumi Nath; Kumar, Sushil
    Plants of the garden pea Pisum sativum an annual Papilionaceae species which have a mutation in the COCHLEATA (COCH) gene bear compound stipules of leaf morphology and secondary inflorescences in which flowers are borne in axils of bracteoles on an inflorescence stem. In the wild-type P. sativum stipules are simple foliaceous and flowers are non-bracteolated. Mutants of the coch phenotype are not known in any other plant species. The COCH gene of P. sativum is not yet sequenced. Therefore whether or not the COCH gene is present in species other than P. sativum remains unknown. Based on the principle of parallel evolution, it is thought that there may be leguminous species that possess the coch phenotype. In search of coch species, the Leguminosae flora of Delhi was surveyed for species that demonstrate compound stipules and bracteolated inflorescences. Out of 124 reported in the Leguminosae flora of Delhi, only the perennial Caesalpinioideae tree species Delonix regia and the shrubby vine species Caesalpinia bonduc were observed to have features of the coch mutants of P. sativum. Since the traits of simple foliaceous stipules and bracteoleless secondary inflorescences of wild-type P. sativum are common to many species among more than 19,400 species of family Leguminosae, it is hypothesized that the COCH gene may be as common as the ubiquitously present LEAFY gene (orthologue of UNIFOLIATA gene of P. sativum) in angiosperms.
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    Genetic analysis of structure and function of stipules in pea (Pisum sativum)
    (Indian National Science Academy, 2012) Sharma, Vishakha; Sinha, Alok Krishna; Chaudhary, Swati; Priyadarshini, Anupama; Tripathi, Bhumi Nath; Kumar, Sushil
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    A comprehensive study on dehydration-induced antioxidative responses during germination of Indian bread wheat (Triticum aestivum L. em Thell) cultivars collected from different agroclimatic zones
    (Springer Science, 2012) Garg, Bharti; Jaiswal, Jai P.; Misra, Shrilekha; Tripathi, Bhumi Nath; Prasad, Manoj
    To explore the adaptability of bread wheat to dehydration stress, we screened 28 cultivars collected from different agroclimatic zones, on the basis of malonaldehyde content as biochemical marker in roots of wheat seedlings during germination and classified them as highly tolerant, tolerant, sensitive and highly sensitive. From this primary screening, ten cultivars that showed differential responses to dehydration stress were selected to understand the biochemical and physiological basis of stress tolerance mechanisms. The highly tolerant cultivars showed lower levels of lipid peroxidation, less membrane damage, increased levels of antioxidants, enzymes like catalase, ascorbate peroxidase, glutathione reductase activities, and maintained higher relative water content in comparison to sensitive cultivars, indicating better protection mechanism operating in tolerant cultivars. Correspondingly, highly tolerant cultivars exhibited more accumulation of proline and less H2O2 content across different time points of polyethylene glycol treatments in comparison to sensitive ones. The above biochemical and physiological parameters were further validated through northern analysis of catalase (CAT1) gene, that showed differential expression patterns in tolerant and sensitive cultivars largely in confirmation with the biochemical and physiological analyses. Our study positively correlates the differences in the redox status and antioxidant defense system between tolerant and sensitive cultivars for the establishment of wheat seedlings in typical dehydration conditions.
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    Characterization and genetic linkage mapping of the horticulturally important mutation leafless inflorescence (lli) in periwinkle Catharanthus roseus
    (Elsevier, 2011) Chaudhary, Swati; Sharma, Vishakha; Prasad, Manoj; Bhatia, Sabhyata; Tripathi, Bhumi Nath; Yadav, Gitanjali; Kumar, Sushil
    Catharanthus roseus is a seasonal to perennial garden plant and the exclusive source of the anticancer drugs vincristine and vinblastine. Its horticultural importance is due to the compound racemose inflorescence architecture of branches in which pairs of prominent flowers are subtended by one of the two leaves per node. Here is reported the construction of a molecular framework genetic linkage map and mapping on it of the LEAF-LESS INFLORESCENCE (LLI) locus. It is quantitatively shown that the adult lli mutant plants produce altered inflorescence of improved horticultural value, wherein axes are excessively branched, two flowers are formed per node that are bare of subtending leaves, and several times more open flowers are displayed each day, as compared to LLI plants.