Accumulation of SALT protein in rice plants as a response to environmental stresses

The SALT protein is a 14.5 kDa mannose-binding lectin originally described as preferentially expressed in rice plant roots in response to NaCl stress. Here, we studied the expression of the SALT polypeptide in rice plants submitted to different stress cues, by immunodetection of SALT protein in plant tissue extracts and using a rabbit polyclonal antibody raised to recombinant SALT protein. High levels of expression of SALT protein were detected in sheath extracts from plants treated with 170 mM NaCl, 170 mM KCl, dehydration, wounding, heat (42 C) or abscisic acid. Even in the absence of stressor added, SALT protein was detected in extracts from seeds collected at early stages of development. SALT protein expression was induced in different levels by salinity in sheaths of several rice cultivars. However, analysis of the damage caused in photochemical efficiency of photosynthesis under salinity conditions in these cultivars revealed no correlation between the levels of SALT protein expression and sensitivity to the stress. These data indicate that the expression of SALT protein is not restricted to responses to environmental stresses and that high levels of expression of SALT protein do not confer tolerance to salinity. It is suggested that the SALT protein participates in a global response/sensor mechanism. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.