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Author: search.filters.author.Sharma, VishakhaSubject: search.filters.subject.Pisum sativum

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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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    Nodal spine pairs present in the mimosoid Prosopis juliflora are not stipules but define a distinct class of lateral organs
    (Scientific Research Publishing Inc., 2012) Sharma, Vishakha; Kumar, Sushil
    The descriptions of Prosopis juliflora of subfamily mimosoideae in the family leguminosae, given in the floras of arid and semi-arid regions of the world, including the flora of Delhi, state that the spine pairs seen in association with compound leaf on nodes are stipules. The suggestions that spines are stipules were tested by morphological and histological examination of nodes of P. juliflora plants growing in the Arawalli range at New Delhi. The nascent nodes on growing branches of P. juliflora were observed to produce a pair of knife-like free bifacial stipules together with a leaf and a pair of spines. The stipules were missing from the mature nodes of the same branches whose young nodes carried stipule pairs, suggesting that the stipules were deciduous whereas leaves and spines were persistent. Anatomically, spines were observed to be appendages to stem and located adjacent to leaf petiole away from stipules. Vasculature of stipules was independent. The observations allowed the conclusion that P. juliflora nodes form regular stipules and spines produced on them are stem-like distinct lateral organs. It is suggested that nodal spine pairs borne on plant nodes in general are lateral organs different from stipules, leaves and secondary inflorescences.
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    COCHLEATA controls leaf size and secondary inflorescence architecture via negative regulation of UNIFOLIATA (LEAFY ortholog) gene in garden pea Pisum sativum
    (Indian Academy of Sciences, 2012) Sharma, Vishakha; Chaudhary, Swati; Kumar, Arvind; Kumar, Sushil
    UNIFOLIATA [(UNI) or UNIFOLIATA-TENDRILLED ACACIA (UNI-TAC)] expression is known to be negatively regulated by COCHLEATA (COCH) in the differentiating stipules and flowers of Pisum sativum. In this study, additional roles of UNI and COCH in P. sativum were investigated. Comparative phenotyping revealed pleiotropic differences between COCH (UNI-TAC and uni-tac) and coch (UNI-TAC and uni-tac) genotypes of common genetic background. Secondary inflorescences were bracteole-less and bracteolated in COCH and coch genotypes, respectively. In comparison to the leaves and corresponding sub-organs and tissues produced on COCH plants, coch plants produced leaves of 1.5-fold higher biomass, 1.5-fold broader petioles and leaflets that were 1.8-fold larger in span and 1.2-fold dorso-ventrally thicker. coch leaflets possessed epidermal cells 1.3-fold larger in number and size, 1.4-fold larger spongy parenchyma cells and primary vascular bundles with 1.2-fold larger diameter. The transcript levels of UNI were at least 2-fold higher in coch leaves and secondary inflorescences than the corresponding COCH organs. It was concluded that COCH negatively regulated UNI in the differentiating leaves and secondary inflorescences and thereby controlled their sizes and/or structures. It was also surmised that COCH and UNI (LFY homolog) occur together widely in stipulate flowering plants.
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    Interaction between COCHLEATA and UNIFOLIATA genes enables normal flower morphogenesis in the garden pea, Pisum sativum
    (Indian Academy of Sciences, 2011) Kumar, Sushil; Sharma, Vishakha; Chaudhary, Swati; Kumari, Renu; Kumari, Nisha; Mishra, Poonam
    The simple stipules, leaflet and tendril bearing imparipinnately compound leaf blades and zygomorphic flowers, produced on stems of the diploid (2n = 14; ≥ 5000 Mbp nuclear genome) papilionoid Fabaceae plant Pisum sativum, are serving as unique and highly informative models for the dis- section of plant developmental programmes. The growing information has revealed that the processes of stipule, leaf and flower morphogeneses are genetically interconnected in P. sativum (Hofer et al. 1997; Yaxley et al. 2001; Wang et al.2008; Kumar et al. 2009).
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    Genetic control of leaf-blade morphogenesis by the Insecatus gene in Pisum sativum
    (Indian Academy of Sciences, 2010) Kumar, Sushil; Chaudhary, Swati; Sharma, Vishakha; Kumari, Renu; Mishra, Raghvendra Kumar; Kumar, Arvind; Choudhury, Debjani Roy; Jha, Ruchi; Priyadarshini, Anupama; Kumar, Arun
    To understand the role of INSECATUS (INS) gene in pea, the leaf blades of wild-type, ins mutant and seven other genotypes, constructed by recombining ins with uni-tac, af, tl and mfp gene mutations, were quantitatively compared. The ins was inherited as a recessive mutant allele and expressed its phenotype in proximal leaflets of full size leaf blades. In ins leaflets, the midvein development was arrested in distal domain and a cleft was formed in lamina above this point. There was change in the identity of ins leaflets such that the intercalary interrupted midvein bore a leaf blade. Such adventitious blades in ins, ins tl and ins tl mfp were like the distal segment of respective main leaf blade. The ins phenotype was not seen in ins af and ins af uni-tac genotypes. There was epistasis of uni-tac over ins. The ins, tl and mfp mutations interacted synergistically to produce highly pronounced ins phenotype in the ins tl mfp triple mutant. The role(s) of INS in leaf-blade organogenesis are: positive regulation of vascular patterning in leaflets, repression of UNI activity in leaflet primordia for ectopic growth and in leaf-blade primordium for indeterminate growth of rachis, delimitation of proximal leaflet domain and together with TL and MFP homeostasis for meristematic activity in leaflet primordia. The variant apically bifid shape of the affected ins leaflets demonstrated that the leaflet shape is dependent on the venation pattern.