Editors' ChoicePlant biology

Exercising Self-Restraint in Plants

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Science's STKE  13 Mar 2001:
Vol. 2001, Issue 73, pp. tw7
DOI: 10.1126/stke.2001.73.tw7

The plant Brassica oleracea prevents self-pollination by relying on the ligand-dependent activation of the serine-threonine-specific S-locus receptor kinase (SRK). Cabrillac et al. have now characterized the kinase activity of the receptor. The putative receptor ligand, a pollen coat protein (PCP), induced the phosphorylation of SRK in vivo. However experiments in vitro with recombinant SRK protein expressed in insect cells showed that the kinase was constitutively active and that extracts of stigma cells contained a factor that inhibited the activity of SRK. Cabrillac et al. showed that two thioredoxin-h-like proteins THL1 and THL2, previously shown to bind to SRK, inhibited its kinase activity in a manner that required the catalytic activity of the thioredoxin. Depletion of thioredoxins also removed the inhibitory activity of stigma extracts. The authors hypothesize that thioredoxins act to restrain SRK activity and that such inhibition is relieved in the presence of PCP after self-pollination.

D. Cabrillac, J. M. Cock, C. Dumas, T. Gaude, The S-locus receptor kinase is inhibited by thioredoxins and activated by pollen coat proteins. Nature 410, 220-223 (2001). [Online Journal]

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