Characterization of a Novel Protein Induced by Progressive or Rapid Drought and Salinity in Brassica napus Leaves

Abstract

Under progressive drought stress, Brassica napus displays differential leaf modifications. The oldest leaves, developed before the onset of water deficit, wilt gradually, whereas the youngest leaves harden. Hardening was distinguished by leaf turgor and bluish wax bloom when the shoot water potential was below -3 MPa and the leaf water saturation deficit was about 60%. This adaptive change was accompanied by modifications in two-dimensional protein profiles. Ten percent of the polypeptides had altered abundance or were unique to drought-stressed plants. Two-dimensional analysis of in vitro translation products did not reveal a general decrease in mRNA population. A 22-kD double polypeptide was increased by progressive or rapid water stress and salinity and disappeared upon rehydration. These polypeptides have a common N-terminal sequence, which does not reveal homology with any known waterstress protein but which contains the signature motif of soybean Kunitz trypsin inhibitors. Immunoprecipitation allowed these polypeptides to be identified on two-dimensional gels of in vitro translation products. They appeared to be synthesized as a 24-kD precursor, and their transcript was present in the control wellwatered leaves, where the polypeptides were never detected, indicating a possible translational regulation. A putative function of this protein, named BnD22, in the retardation of drought-induced leaf senescence is discussed.Rapeseed (Brassica napus L. var oleifera) is often subjected to various environmental stresses (cold, flooding, salinity, etc.). In humid and temperate areas, drought periods are a major factor impeding plant growth and development. This species, like other Cruciferae species, displays an original adaptive strategy. When subjected to progressive drought stress, a dramatic alteration of its root system occurs, characterized by the emergence of numerous roots that remain short, hairless, and often tuberized (3). These roots are able to survive extreme soil desiccation and rapidly recover hair formation and elongation upon rehydration. A specific be-

Response of Vicia faba plants to the interactive effect of sodium chloride salinity and salicylic acid treatment

“…Reviron et al (1992) detected a 22-kDa protein in Brassica napus plants subjected to water and salt stresses which disappeared upon rehydration. Gupta (1999) identified two polypeptides with molecular masses of 60 and 18 kDa in selected embryos and plants of salt-treated orchard grass.…”

“…Reviron et al (1992) detected a 22-kDa polypeptide protein in Brassica napus plants subjected to water or salt stresses, but the polypeptide disappeared upon rehydration. Singh et al (1987) and Kononowicz et al (1992) demonstrated that a 26-kDa protein referred to as osmotin was intimately associated with salt adaptation in cultured tobacco cells.…”

Structural Changes in Senescing Oilseed Rape Leaves at Tissue and Subcellular Levels Monitored by Nuclear Magnetic Resonance Relaxometry through Water Status

“…In Arabidopsis (Arabidopsis thaliana) and oilseed rape, N can be remobilized from old to expanding leaves at the vegetative stage during sequential senescence as well as from leaves to seeds at the reproductive stage during monocarpic senescence (Malagoli et al, 2005;Diaz et al, 2008; Lemaitre et al, 2008). Senescence can also be induced by environmental stress such as N starvation (Etienne et al, 2007) or water deficit (Reviron et al, 1992) and propagated from old to mature leaves and delayed in young leaves, suggesting finely tuned high regulation of metabolism at the whole-plant level with consequences for NUE (Desclos et al, 2008). One major challenge to understanding the efficiency of senescenceinduced organic resource reallocation and to highlighting major molecular and mechanistic attributes of nutrient recycling is monitoring the kinetics of the structural reorganization of cell structures.…”

Characterization of a Salt-Responsive 24-Kilodalton Glycoprotein in Mesembryanthemum crystallinum

“…We found that Pro levels increased more than 13-fold when light-grown callus was transferred to 200 mM NaCl, whereas the activity of phosphoenolpyruvate carboxylase, the key enzyme for performing CAM, remained relatively constant (Yen, 1993). Because of their ability to survive in high concentrations of NaCl without inducing CAM, these cultured cells were used to study the halotolerance mechanism of this plant at the cellular level.The synthesis of severa1 proteins located in either the cytosol (Hurkman and Tanaka, 1987;Zhao et al, 1989;Reviron et al, 1992), membrane fractions (Singh et al, 1987a; Hurkman et al, 1988), chloroplasts (Winicov andButton, 1991), or intercellular space (Bozarth et al, 1987;Iraki et al, 1989;Esaka et al, 1992) was found to be either up-or downregulated by osmotic stress. In most cases, however, the function of these polypeptides is presently unknown.…”

“…The synthesis of severa1 proteins located in either the cytosol (Hurkman and Tanaka, 1987;Zhao et al, 1989;Reviron et al, 1992), membrane fractions (Singh et al, 1987a; Hurkman et al, 1988), chloroplasts (Winicov andButton, 1991), or intercellular space (Bozarth et al, 1987;Iraki et al, 1989;Esaka et al, 1992) was found to be either up-or downregulated by osmotic stress. In most cases, however, the function of these polypeptides is presently unknown.…”