Natriuretic peptide hormones promote radial water movements from the xylem of Tradescantia shoots |
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Authors: | I N Suwastika C A Gehring |
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Institution: | (1) Deakin University, School of Biological and Chemical Sciences, Geelong, Victoria 3217 (Australia), Fax +61 3 5227 2022, e-mail: cage@deakin.edu.au, AU |
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Abstract: | Immunological evidence suggests that plants, like vertebrates, contain natriuretic peptides (NPs) and that rat atrial NP
(rANP) binds specifically to plant membranes and promotes concentration and conformation-dependent stomatal opening. Stomatal
opening and specific increases in cGMP levels were also observed in response to immunoreactive plant NP (irPNP). Here we report
that both 1 μM rANP and irPNP (100 ng total protein/100 μL) significantly increase radial water movements out of the xylem
of shoots of Tradescantia multiflora. Enhanced radial water movements are also observed in response to the cell permeant cGMP analogue 8-Br-cGMP (100 nM). The
water channel inhibitor mercuric chloride (HgCl2) significantly inhibits radial water movements at concentrations of 50 μM, while the presence of 10 μM 2-hydroxyethylmercaptoethanol
(ME) prevents the inhibitory effect of the mercurial. The guanylate cyclase inhibitor LY 83583 at a concentration of 20 μM
and sodium azide (NaN3) at concentrations of ≥ 1 μM both also reduce radial water movements. We therefore conclude that the regulation of radial
water movement out of the xylem involves modulation of cGMP levels, water channels and respiration-dependent processes. In
addition, we propose that NPs have a critical role to play in radial water movements out of the xylem and speculate that as
in vertebrates, NP effects might, at least in part, be mediated via the regulation of guanylate cyclases and water channels.
Received 15 June 1998; received after revision 7 August 1998; accepted 26 August 1998 |
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Keywords: | , Natriuretic peptides in plants, water channels, cGMP, HgCl2, 2H NMR, |
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