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Self-incompatibility in Papaver targets soluble inorganic pyrophosphatases in pollen

De Graaf, Barend H. J. ORCID:, Rudd, Jason J., Wheeler, M. J., Perry, R. M., Bell, E. M., Osman, K., Franklin, F. C. H. and Franklin-Tong, V. E. 2006. Self-incompatibility in Papaver targets soluble inorganic pyrophosphatases in pollen. Nature 444 , pp. 490-493. 10.1038/nature05311

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In higher plants, sexual reproduction involves interactions between pollen and pistil. A key mechanism to prevent inbreeding is self-incompatibility through rejection of incompatible ('self') pollen1. In Papaver rhoeas, S proteins encoded by the stigma interact with incompatible pollen, triggering a Ca2+-dependent signalling network2, 3, 4, 5 resulting in pollen tube inhibition and programmed cell death6. The cytosolic phosphoprotein p26.1, which has been identified in incompatible pollen, shows rapid, self-incompatibility-induced Ca2+-dependent hyperphosphorylation in vivo3. Here we show that p26.1 comprises two proteins, Pr-p26.1a and Pr-p26.1b, which are soluble inorganic pyrophosphatases (sPPases). These proteins have classic Mg2+-dependent sPPase activity, which is inhibited by Ca2+, and unexpectedly can be phosphorylated in vitro. We show that phosphorylation inhibits sPPase activity, establishing a previously unknown mechanism for regulating eukaryotic sPPases. Reduced sPPase activity is predicted to result in the inhibition of many biosynthetic pathways, suggesting that there may be additional mechanisms of self-incompatibility-mediated pollen tube inhibition. We provide evidence that sPPases are required for growth and that self-incompatibility results in an increase in inorganic pyrophosphate, implying a functional role for Pr-p26.1.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Biosciences
Publisher: Nature Publishing Group
ISSN: 0028-0836
Last Modified: 25 Oct 2022 10:06

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