Premium
Proteolysis and nitrogen fixation in faba‐bean ( Vicia faba ) nodules under water stress
Author(s) -
Guérin Vincent,
Pladys Dominique,
Trinchant JeanCharles,
Rigaud Jean
Publication year - 1991
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 - 10.1111/j.1399-3054.1991.tb02918.x
Subject(s) - vicia faba , leghemoglobin , nitrogen fixation , proteolysis , proteases , biology , nitrogenase , nitrogen , botany , chemistry , horticulture , biochemistry , root nodule , enzyme , organic chemistry
Nodulated faba‐beans ( Vicia faba L. var. minor) exhibiting high rates of N 2 fixation (133 μmol C 2 H 4 g −1 dry weight h −1 ), were subjected to water restriction. A loss of C 2 H 2 reduction due to water stress was always associated with a decline of the leghemoglobin content for each of the 4 decreasing values of Ψ mod . Electron micrographs showed ultrastructural alterations of the fixing tissue, which affected both partners and increased with the severity of water stress. In the nodule cytosol, the alkaline proteolysis approximately doubled when Ψ mod decreased from −0.55 MPa to −1.55 MPa. Concomitantly, an increase of the nodule intracellular pH from 6.3 to 7.0 was observed. Proteolysis was due to serine proteases, exhibiting a pH‐optimum of 8 and which actively degraded purified leghemoglobin in vitro (K m =100 μ M ). The degradation of leghemoglobin during water stress may contribute to the loss of C 2 H 2 reduction and may affect the pattern of recovery upon rewatering.