title: Thioredoxin h isoforms from rice are differentially reduced by NADPH/thioredoxin or GSH/glutaredoxin systems.
abstract: Rice (Oryza sativa L.) has multiple potential genes encoding thioredoxin (Trx) h and NADP-thioredoxin reductase (NTR). These NTR and Trx h isoforms, known as cytoplasmic NTR/Trx system along with multiple members of glutaredoxin (Grx) family constitute a complex redox control system in rice. In the present study, we investigated the kinetic parameters of two rice NTRs, OsNTRA and OsNTRB, toward three endogenous Trx h isoforms, OsTrx1, OsTrx20, and OsTrx23. The results showed that in contrast with OsTrx1 and OsTrx23, the isoform OsTrx20 was not reduced by OsNTR isoforms. The kcat/Km values of OsNTRB and OsNTRA toward OsTrx1 was six- and 13-fold higher than those values toward OsTrx23, respectively, suggesting that OsNTR isoforms do not reduce different OsTrx h isoforms, equivalently. Furthermore, the possible reduction of OsTrx isoforms by the glutathione (GSH)/Grx system was investigated through the heterologous expression of a gene encoding OsGrx9, a bicysteinic CPYC Grx found in rice. Whereas OsTrx23 was not reduced by GSH, OsTrx20 and with less efficiently OsTrx1 were reduced by GSH or GSH/Grx. Therefore, it seems that OsTrx1 can be reduced either by OsNTR or GSH/Grx. These data for the first time provides an evidence for cross-talking between NTR/Trx and GSH/Grx systems in rice.
authors.affiliation: Department of Agricultural Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
authors.forename: Ehsan
authors.initials: E
authors.lastname: Shaykholeslam Esfahani
authors.affiliation: Department of Agricultural Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran. Electronic address: a.shahpiri@cc.iut.ac.ir.
authors.forename: Azar
authors.initials: A
authors.lastname: Shahpiri
mesh_terms: D004789:Enzyme Activation; D051456:Gene Flow; D054477:Glutaredoxins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism*; D009249:NADP / Q000378:metabolism*; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA; D054480:Thioredoxin h / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D013880:Thioredoxin-Disulfide Reductase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism*
chemical_list: D054477:Glutaredoxins; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D054480:Thioredoxin h; D013879:Thioredoxins; D009249:NADP; D013880:Thioredoxin-Disulfide Reductase; D005978:Glutathione
keywords: Glutaredoxin; Glutathione; NADPH-dependent thioredoxin reductase; Rice; Thioredoxin h