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SUMMARY:Identification of ADPR cyclase in Arabidopsis - SM Abdul Awal
DTSTART:20120504T120000Z
DTEND:20120504T123000Z
UID:TALK36378@talks.cam.ac.uk
CONTACT:Suzy Stoodley
DESCRIPTION:ADP-ribosyl cyclase (ADPR cyclase) is involved in calcium home
 ostasis and shows ubiquitous activity in different tissues of marine inver
 tebrates\, amphibians\, avians and mammals including humans. ADPR cyclase 
 is a multifunctional enzyme that catalyses NAD and NADP into the two impor
 tant second massengers cyclic adenosine diphosphoribose (cADPR) and nicoti
 nic acid adenine dinucleotide phosphate (NAADP) respectively. It also cata
 lyses the hydrolysis of cADPR to produce nicotinamide and ADP ribose. cADP
 R targets the ryanodine receptor (RyR) present in the sarco/endoplasmic re
 ticulum (ER)\, whilst NAADP targets the two-pore channel (TPC) in the endo
 lysosomes. Together they act as potent calcium mobilizers in the cell. cAD
 PR elevates (Ca2+)cyt in plants and plays a central role in signal transdu
 ction pathways evoked by the drought and stress hormone\, abscisic acid (A
 BA). Despite evidence for the action of cADPR in plant cells\, no proteins
  with significant similarity to the known ADPR cyclases have been identifi
 ed in any plant genome database\, suggesting that proteins with very low h
 omology or a unique mechanism for cADPR synthesis must exist in plant cell
 s. As the amount of this membrane bound protein is very low in plant cells
 \, we are trying to apply pharmacological approaches using agonists (NaCl\
 , H2O2\, NO and cold water) and antagonists (nicotinamide\, 8-Br-cADPR\, M
 g2+) in order to increase the ADPR cyclase activity. Among the screened ag
 onists\, we found that NO is a potential candidate for increasing the acti
 vity of ADPR cyclase in Arabidopsis. We confirmed the presence of ADPR cyc
 lase in the cytosol of this plant by the NGD fluorescence-based cycling as
 say and are trying to develop a new method\, reverse cyclase assay\, to me
 asure low basal ADPR cyclase activity in Arabidopsis. In addition\, we cha
 racterized Arabidopsis transformed with 35S:ADPRc by germination and flowe
 ring time assays. Although over expression of ADPR cyclase in the plant di
 d not show significant difference in flowering time in SD conditions compa
 red with wild type\, a statistically significant difference in leaf number
  was observed in LD conditions. Furthermore\, delayed germination was obse
 rved in 35S:ADPRc plants compared to wild-type when treated with ABA confi
 rming the relationship of ABA and cADPR.
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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