Expression of the human NAD(P)-metabolizing ectoenzyme CD38 compromises systemic acquired resistance in Arabidopsis.
Plant systemic acquired resistance (SAR) is a long-lasting, broad-spectrum immune response that is mounted after primary pathogen infection. Although SAR has been extensively researched, the molecular mechanisms underlying its activation have not been completely understood. We have previously shown that the electron carrier NAD(P) leaks into the plant extracellular compartment upon pathogen attack and that exogenous NAD(P) activates defense gene expression and disease resistance in local treated leaves, suggesting that extracellular NAD(P) [eNAD(P)] might function as a signal molecule activating plant immune responses. To further establish the function of eNAD(P) in plant immunity, we tested the effect of exogenous NAD(P) on resistance gene-mediated hypersensitive response (HR) and SAR. We found that exogenous NAD(P) completely suppresses HR-mediated cell death but does not affect HR-mediated disease resistance. Local application of exogenous NAD(P) is unable to induce SAR in distal tissues, indicating that eNAD(P) is not a sufficient signal for SAR activation. Using transgenic Arabidopsis plants expressing the human NAD(P)-metabolizing ectoenzyme CD38, we demonstrated that altering eNAD(P) concentration or signaling compromises biological induction of SAR. This result suggests that eNAD(P) may play a critical signaling role in activation of SAR.
Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, USA.
Xudong
X
Zhang
Zhonglin
Z
Mou
D051997:ADP-ribosyl Cyclase 1 / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D009249:NADP / Q000494:pharmacology*; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology*; D030821:Plants, Genetically Modified; D021381:Protein Transport; D015398:Signal Transduction; D013997:Time Factors
D008562:Membrane Glycoproteins; D009249:NADP; C498154:CD38 protein, human; D051997:ADP-ribosyl Cyclase 1