A role for plant natriuretic peptide immuno-analogues in NaCl- and drought-stress responses |
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Authors: | Suhail Rafudeen Gugu Gxaba Gile Makgoke G Bradley Ganka Pironcheva Lincoln Raitt Helen Irving Chris Gehring |
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Institution: | Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa; Department of Botany, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa; Department of Pharmaceutical Biology and Pharmacology, Victorian College of Pharmacy, Monash University, 381 Royal Parade, Parkville, Melbourne, Victoria 3052, Australia |
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Abstract: | Higher plants contain biologically active molecules that are recognized by anti-human atrial natriuretic polypeptide rabbit serum (anti-ANP). These molecules are termed immunoreactant plant natriuretic peptides (irPNPs) and have previously been shown to be associated with conductive tissue and to affect ion fluxes, protoplast volume regulation and stomatal guard cell responses. Herein an irPNP from the brassicaceus weed Erucastrum strigosum is identified and it is demonstrated that the relative amounts of irPNP expressed as a percentage of total water : methanol (50 : 50) extracted proteins are increased when plants are exposed to 300 m M NaCl. Since 100 and 200 m M NaCl reduce dry and fresh mass as well as increase total tissue NaCl load, it is hypothesized that irPNP up-regulation is a late and possibly adaptive response. IrPNP is also significantly up-regulated in Arabidopsis thaliana suspension culture cells in response to 150 m M NaCl and even more so in response to iso-osmolar amounts of sorbitol. Finally, a recombinant A. thaliana irPNP (AtPNP-A) promotes net water-uptake into the protoplast and thus volume increases. This response is dependent on de novo protein synthesis and may suggest a complex and possibly regulatory function for irPNP-like molecules in plant homeostasis. |
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