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Isolation of photorespiratory mutants from Lotus japonicus deficient in glutamine synthetase
Author(s) -
Orea Alicia,
Pajuelo Purificación,
Pajuelo Eloísa,
Quidiello Concepción,
Romero José M.,
Márquez Antonio J.
Publication year - 2002
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.1399-3054.2002.1150304.x
Subject(s) - mutant , glutamine synthetase , biology , lotus japonicus , complementation , gene isoform , biochemistry , wild type , isozyme , ammonium , mutagenesis , glutamine , botany , microbiology and biotechnology , gene , enzyme , amino acid , chemistry , organic chemistry
A mutagenesis programme using ethyl methanesulphonate (EMS) was carried out on Lotus japonicus (Regel) Larsen cv. Gifu in order to isolate photorespiratory mutants in this model legume. These mutants were able to grow in a CO 2 ‐enriched atmosphere [0.7% (v/v) CO 2 ] but showed stress symptoms when transferred to air. Among them, three mutants displayed low levels of glutamine synthetase (GS; EC 6.3.1.2) activity in leaves. The mutants accumulated ammonium in leaves upon transfer from 0.7% (v/v) CO 2 to air. F 1 plants of back crosses to wild type were viable in air and F 2 populations segregated 3 : 1 (viable in air : air‐sensitive) indicative of a single Mendelian recessive trait. Complementation tests showed that the three mutants obtained were allelic. Chromatography on DEAE‐Sephacel used to separate the cytosolic and plastidic GS isoenzymes together with immunological data showed that: (1) mutants were specifically affected in the plastidic GS isoform, and (2) in L. japonicus the plastidic GS isoform eluted at lower ionic strength than the cytosolic isoform, contrary to what happens in most plants. The plastidic GS isoform present in roots of wild type L. japonicus was also absent in roots of the mutants, indicating that this plastidic isoform from roots was encoded by the same gene than the GS isoform expressed in leaf tissue. Viability of mutant plants in high‐CO 2 conditions indicates that plastidic GS is not essentially required for primary ammonium assimilation. Nevertheless, mutant plants did not grow as well as wild type plants in high‐CO 2 conditions.