Browsing by Author "Nayyar, H."

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    Temperature-stratified screening of chickpea (Cicer arietinum L.) genetic resource collections reveals very limited reproductive chilling tolerance compared to its annual wild relatives
    (2012) Berger, J.D.; Kumar, Sanjeev; Nayyar, H.; Street, K. A.; Sandhu, J. S.; Henzell, J. M.; Kaur, J.; Clark, H.C.
    Low reproductive chilling tolerance in chickpea impairs ovule fertilization, delaying pod set, exposing the crop to terminal drought throughout much of its distribution range. Despite this realization, little progress has been made because of the limited genetic variation available to breeders. To address this issue a wide range of domesticated (n= 1762) and wild Cicer (n= 200) germplasm collected from sites stratified by flowering phase temperature was extensively field evaluated, and compared with Lupinus angustifolius, a well-adapted Mediterranean winter annual. Chilling tolerance was estimated by regressing the time interval between pod set and first flower against mean post-anthesis temperature. Field screening was augmented by smaller scale experiments evaluating the effects of contrasting post-anthesis temperature regimes on plant growth and productivity, pollen function and subsequent pod set in temperature-controlled cabinets.Chickpea was less chilling tolerant than its wild relatives, the flower-pod interval increasing curvi-linearly as sites became cooler, with a strong effects between 11 and 16. ?C, tailing off after 17.5. ?C, but remaining statistically significant. There is little useful variation for chilling tolerance within domesticated chickpea. Small, albeit statistically significant differences in pod set delay in chickpea collected from contrasting flowering phase habitats, were marginal compared to more tolerant species such as Cicer bijugum, Cicer judaicum and L. angustifolius, and to a lesser extent Cicer reticulatum, Cicer pinnatifidum, and Cicer echinospermum. No differences were observed between desi and kabuli types. Field screening identified robust chilling tolerance in a C. echinospermum accession that commenced podding earlier, at lower temperatures (10.0. ?C), and yielded 5 times more than Rupali, the most productive chickpea. Controlled temperature experiments confirmed that in contrast to chickpea, pollen germination, viability, frequency on the stigma surface and subsequent pod set were unaffected by low post-anthesis temperatures (13/7. ?C) in C. echinospermum and L. angustifolius. Our results indicate that chickpea is even more chilling sensitive than previously thought. Because C. echinospermum is inter-fertile with chickpea, it has considerable potential both as a donor of robust chilling tolerance and as an agent for investigating resistance mechanisms. ? 2011.
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    Understanding the multifaceted role of ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2) and its altered behaviour in human diseases
    (Bentham Science Publishers B.V., 2015) Cholia, R.P.; Nayyar, H.; Kumar, R.; Mantha, Anil K.
    Ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2) also known as Autotaxin, is a secreted lysophospholipase D, which hydrolyzes lysophosphatidylcholine (LPC) into Lysophosphatidic acid (LPA). LPA is the bioactive product of ENPP2 enzyme, which induces diverse signalling pathways via six LPA-G-protein coupled receptors (GPCRs). ENPP2 is an essential protein for normal development and its altered expression is associated with various human diseases. Cellular ENPP2 silencing results in lethality at the embryonic stage in mice. Initially, it is identified as an autocrine factor in melanoma cells. Different research groups are currently exploring to understand the multifaceted role of ENPP2 in various processes such as embryonic and neural development, migration, invasion, differentiation, proliferation, angiogenesis, and survival. Altered expression of ENPP2 is also associated with various diseases like inflammation, cancer, fibrosis, rheumatoid arthritis and neural defects. In this article, we have summarized structural aspects of ENPP2 and biochemical functions associated with its diverse cellular roles in various human diseases including cancer and Alzheimer's disease (AD). In addition, keeping in view and advocating findings, a note on various phytochemicals and synthetic inhibitors, which are currently explored as therapeutic agents targeting functions of ENPP2 for the treatment of various human diseases is also presented. ? 2015 Bentham Science Publishers.