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Farnesylation mediates brassinosteroid biosynthesis to regulate abscisic acid responses


Protein farnesylation is a post-translational modification involving the addition of a 15-carbon farnesyl isoprenoid to the carboxy terminus of select proteins1–3. Although the roles of this lipid modification are clear in both fungal and animal signalling, many of the mechanistic functions of farnesylation in plant signalling are still unknown. Here, we show that CYP85A2, the cytochrome P450 enzyme that performs the last step in brassinosteroid biosynthesis (conversion of castasterone to brassinolide)4, must be farnesylated to function in Arabidopsis. Loss of either CYP85A2 or CYP85A2 farnesylation results in reduced brassinolide accumulation and increased plant responsiveness to the hormone abscisic acid (ABA) and overall drought tolerance, explaining previous observations5. This result not only directly links farnesylation to brassinosteroid biosynthesis but also suggests new strategies to maintain crop yield under challenging climatic conditions.

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Figure 1: cyp85a2-2 and era1-2 mutants have overlapping phenotypes.
Figure 2: Lack of ERA1 results in reduced brassinolide accumulation.
Figure 3: Farnesylation is required for CYP85A2 function.
Figure 4: Farnesylation of CYP85A2 is required for ER localization.


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This work was supported by Natural Sciences and Engineering Research Council of Canada funding for P.M. and M.A.S. We thank S. Urquhart (University of Tasmania) for assistance with hormone extraction and D. Nichols and N. Davies (University of Tasmania) for assistance with hormone quantification. We thank D. K. Ro (University of Calgary) for helpful discussions on cytochrome p450 enzymes and their functions.

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Authors and Affiliations



J.N., P.M. and M.A.S. initiated the project. J.N., S.L., P.M. and M.A.S. designed the research; J.N., S.L., M.J., S.D. and M.A.S. performed all the experiments; E.F. and J.B.R. undertook brassinosteroid quantifications and analysis; J.N., S.L. and M.A.S. analysed data; and P.M. and M.A.S. wrote the manuscript. All authors discussed the results and commented on the manuscript.

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Correspondence to Peter McCourt or Marcus A. Samuel.

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The authors declare no competing financial interests.

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Supplementary Methods, Supplementary References, Supplementary Tables 1-3 and Supplementary Figs 1-7. (PDF 1950 kb)

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Northey, J., Liang, S., Jamshed, M. et al. Farnesylation mediates brassinosteroid biosynthesis to regulate abscisic acid responses. Nature Plants 2, 16114 (2016).

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