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Aldehyde oxidase isoforms and subunit composition in roots of barley as affected by ammonium and nitrate
Author(s) -
Omarov Rustem,
Dräger Dörthe,
Tischner Rudolf,
Lips Herman
Publication year - 2003
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2003.00043.x
Subject(s) - protein subunit , ammonium , biochemistry , gene isoform , substrate (aquarium) , western blot , chemistry , hordeum vulgare , oxidase test , nitrate , biology , enzyme , botany , poaceae , gene , organic chemistry , ecology
Aldehyde oxidase (AO; EC 1.2.3.1) isoforms in roots of barley plants grown on ammonium or nitrate as nitrogen sources were studied. Roots of ammonium‐grown barley plants exhibited considerable levels of AO2, AO3, and AO4 activities after native PAGE. Significantly lower AO2 and AO3 activity bands were observed in roots of plants grown on nitrate. When abscisic aldehyde was used as a substrate a strong response of the AO2 band was observed as well as a faint reaction of the AO3 band, but no activity of AO4 was observed using this substrate. The 160 and 145 kDa polypeptides were detected in ammonium grown plants. Root extracts of nitrate‐fed plants revealed only a minor 145 kDa protein band and none of the 160 kDa subunit was detected. The assembly of the AO3 heterodimer requires the simultaneous presence of 160 and 145 kDa subunits. Subunit analysis of AO2 and AO4 revealed homodimeric composition of 160 and 145 kDa, respectively. Western blot analysis revealed changing AO subunits levels during germination and plant development. Differential expression of AO subunits (160 and 145 kDa) and subsequent formation of isoforms, which differ in substrate specificity, distribution and fulfil different enzymatic reactions, may constitute an important regulatory mechanism in the plant.