Better explicating the strengths and shortcomings of these models will help refine projections and improve transparency in the years ahead.
Image credit: Witsawat.S.
Contributed by Chris R. Somerville, February 12, 2017 (sent for review September 7, 2016; reviewed by Steve C. Huber and Simon R. Turner)
Significance
Cellulose is the most abundant biopolymer on Earth and is a critical component for plants to grow and develop. Cellulose is synthesized by large cellulose synthase complexes containing multiple cellulose synthase A (CESA) subunits; however, how cellulose synthesis is regulated remains unclear. In this study, we identify BRASSINOSTEROID INSENSITIVE2 (BIN2) as a protein kinase that directly phosphorylates Arabidopsis CESA1 and further demonstrate that this phosphorylation event negatively regulates CESA activity, and thus cellulose biosynthesis, in Arabidopsis. Therefore, this study provides a clear link between cell wall biosynthesis and hormonal signal transduction pathways that regulate plant growth and development.
Abstract
The deposition of cellulose is a defining aspect of plant growth and development, but regulation of this process is poorly understood. Here, we demonstrate that the protein kinase BRASSINOSTEROID INSENSITIVE2 (BIN2), a key negative regulator of brassinosteroid (BR) signaling, can phosphorylate Arabidopsis cellulose synthase A1 (CESA1), a subunit of the primary cell wall cellulose synthase complex, and thereby negatively regulate cellulose biosynthesis. Accordingly, point mutations of the BIN2-mediated CESA1 phosphorylation site abolished BIN2-dependent regulation of cellulose synthase activity. Hence, we have uncovered a mechanism for how BR signaling can modulate cellulose synthesis in plants.
Footnotes
↵1C.S.-R. and K.K. contributed equally to this work.
- ↵2To whom correspondence may be addressed. Email: crs{at}berkeley.edu, staffan.persson{at}unimelb.edu.au, or iwallace{at}unr.edu.
↵3S.P. and I.S.W. contributed equally to this work.
Author contributions: C.S.-R., R.S., C.R.S., S.P., and I.S.W. designed research; C.S.-R., K.K., R.S., J.A.V., and I.S.W. performed research; I.S.W. contributed new reagents/analytic tools; C.S.-R., K.K., R.S., J.A.V., C.R.S., S.P., and I.S.W. analyzed data; and C.S.-R., K.K., R.S., C.R.S., S.P., and I.S.W. wrote the paper.
Reviewers: S.C.H., University of Illinois; and S.R.T., University of Manchester.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1615005114/-/DCSupplemental.
BIN2 regulates cellulose synthase
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- Plant Biology
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