Cytokinins initiate secondary growth in the Arabidopsis root through a set of LBD genes

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Ye , L , Wang , X , Lyu , M , Siligato , R , Eswaran , G , Vainio , L , Blomster , T , Zhang , J & Mähönen , A P 2021 , ' Cytokinins initiate secondary growth in the Arabidopsis root through a set of LBD genes ' , Current Biology , vol. 31 , no. 15 , pp. 3365-3373 . https://doi.org/10.1016/j.cub.2021.05.036

Title: Cytokinins initiate secondary growth in the Arabidopsis root through a set of LBD genes
Author: Ye, Lingling; Wang, Xin; Lyu, Munan; Siligato, Riccardo; Eswaran, Gugan; Vainio, Leo; Blomster, Tiina; Zhang, Jing; Mähönen, Ari Pekka
Contributor: University of Helsinki, Helsinki Institute of Life Science HiLIFE
University of Helsinki, Helsinki Institute of Life Science HiLIFE
University of Helsinki, Helsinki Institute of Life Science HiLIFE
University of Helsinki, Biosciences
University of Helsinki, Helsinki Institute of Life Science HiLIFE
University of Helsinki, Helsinki Institute of Life Science HiLIFE
University of Helsinki, Institute of Biotechnology
University of Helsinki, Helsinki Institute of Life Science HiLIFE
University of Helsinki, Helsinki Institute of Life Science HiLIFE
Date: 2021-08-09
Language: eng
Number of pages: 17
Belongs to series: Current Biology
ISSN: 0960-9822
URI: http://hdl.handle.net/10138/333920
Abstract: During primary growth, plant tissues increase their length, and as these tissues mature, they initiate secondary growth to increase thickness.(1) It is not known what activates this transition to secondary growth. Cytokinins are key plant hormones regulating vascular development during both primary and secondary growth. During primary growth of Arabidopsis roots, cytokinins promote procambial cell proliferation(2,3) and vascular patterning together with the hormone auxin.(4-7) In the absence of cytokinins, secondary growth fails to initiate.(8) Enhanced cytokinin levels, in turn, promote secondary growth.(8,9) Despite the importance of cytokinins, little is known about the downstream signaling events in this process. Here, we show that cytokinins and a few downstream LATERAL ORGAN BOUNDARIES DOMAIN (LBD) family of transcription factors are rate limiting components in activating and further promoting secondary growth in Arabidopsis roots. Cytokinins directly activate transcription of two homologous LBD genes, LBD3 and LBD4. Two other homologous LBDs, LBD1 and LBD11, are induced only after prolonged cytokinin treatment. Our genetic studies revealed a two stage mechanism downstream of cytokinin signaling: while LBD3 and LBD4 regulate activation of secondary growth, LBD1, LBD3, LBD4, and LBD11 together promote further radial growth and maintenance of cambial stem cells. LBD overexpression promoted rapid cell growth followed by accelerated cell divisions, thus leading to enhanced secondary growth. Finally, we show that LBDs rapidly inhibit cytokinin signaling. Together, our data suggest that the cambium-promoting LBDs negatively feed back into cytokinin signaling to keep root secondary growth in balance.
Subject: FAMILY
REGULATORS
EXPRESSION
PROTEINS
NETWORK
BINDING
SYSTEM
ROBUST
ROLES
11831 Plant biology
1182 Biochemistry, cell and molecular biology
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