title: A maize defense-inducible gene is a major facilitator superfamily member related to bacterial multidrug resistance efflux antiporters.
abstract: A defense-inducible maize gene was discovered through global mRNA profiling analysis. Its mRNA expression is induced by pathogens and defense-related conditions in various tissues involving both resistant and susceptible interactions. These include Cochliobolus heterostrophus and Cochliobolus carbonum infection, ultraviolet light treatment, the Les9 disease lesion mimic background, and plant tissues engineered to express flavonoids or the avirulence gene avrRxv. The gene was named Zm-mfs1 after it was found to encode a protein related to the major facilitator superfamily (MFS) of intregral membrane permeases. It is most closely related to the bacterial multidrug efflux protein family, typified by the Escherichia coli TetA, which are proton motive force antiporters that export antimicrobial drugs and other compounds, but which can be also involved in potassium export/proton import or potassium re-uptake. Other related plant gene sequences in maize, rice, and Arabidopsis were identified, three of which are introduced here. Among this new plant MFS subfamily, the characteristic MFS motif in cytoplasmic TM2-TM3 loop, and the antiporter family motif in transmembrane domain TM5 are both conserved, however the TM7 and the cytoplasmic TM8-TM9 loop are divergent from those of the bacterial multidrug transporters. We hypothesize that Zm-Mfs1 is a prototype of a new class of plant defense-related proteins that could be involved in either of three nonexclusive roles: (1) export of antimicrobial compounds produced by plant pathogens; (2) export of plant-generated antimicrobial compounds; and (3) potassium export and/or re-uptake, as can occur in plant defense reactions.
authors.affiliation: Bioinformatics Department, Pioneer Hi-Bred International, Inc., 7300 N.W. 62nd Avenue, Johnston, IA 50131-1004, USA. carl.simmons@pioneer.com
authors.forename: Carl R
authors.initials: CR
authors.lastname: Simmons
authors.forename: Marcelo
authors.initials: M
authors.lastname: Fridlender
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Navarro
authors.forename: Nasser
authors.initials: N
authors.lastname: Yalpani
mesh_terms: D000595:Amino Acid Sequence; D017920:Antiporters / Q000235:genetics*; D001203:Ascomycota / Q000254:growth & development*; D015152:Blotting, Northern; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D007113:Immunity, Innate / Q000235:genetics; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014466:Ultraviolet Rays; D003313:Zea mays / Q000235:genetics* / Q000382:microbiology / Q000528:radiation effects
chemical_list: D017920:Antiporters; D018076:DNA, Complementary; D010940:Plant Proteins; D012333:RNA, Messenger