The Asymmetric Expression of SAUR Genes Mediated by ARF7/19 Promotes the Gravitropism and Phototropism of Plant Hypocotyls

Xiaoyi Wang,Renbo Yu,Jiajun Wang,Zechuan Lin,Xue Han,Zhaoguo Deng,Liumin Fan,Hang He,Xing Wang Deng,Haodong Chen

doi:10.1016/j.celrep.2020.107529

Xiaoyi Wang, Renbo Yu + Show 8 more

Open Access

https://doi.org/10.1016/j.celrep.2020.107529

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Journal: Cell Reports	Publication Date: Apr 1, 2020
Citations: 36	License type: cc-by

Affiliation: Center for Life Sciences, Peking University

Abstract

The asymmetric distribution of auxin leads to the bending growth of hypocotyls during gravitropic and phototropic responses, but the signaling events downstream of auxin remain unclear. Here, we identify many SAUR genes showing asymmetric expression in soybean hypocotyls during gravistimulation and then study their homologs in Arabidopsis. SAUR19 subfamily genes have asymmetric expression in Arabidopsis hypocotyls during gravitropic and phototropic responses, induced by the lateral redistribution of auxin. Both the mutation of SAUR19 subfamily genes and the ectopic expression of SAUR19 weaken these tropic responses, indicating the critical role of their asymmetric expression. The auxin-responsive transcription factor ARF7 may directly bind the SAUR19 promoter and activate SAUR19 expression asymmetrically in tropic responses. Taken together, our results reveal that a gravity- or light-triggered asymmetric auxin distribution induces the asymmetric expression of SAUR19 subfamily genes by ARF7 and ARF19 in the hypocotyls, which leads to bending growth during gravitropic and phototropic responses.

Highlights

Gravity and light are two of the most important environmental factors affecting the growth and development of plants at multiple stages (Morita and Tasaka, 2005; Whippo and Hangarter, 2006)
We further studied the SAUR19 subfamily genes of Arabidopsis, which are homologs of the SAURs identified in soybean, and revealed important roles of these genes in both the gravitropic and phototropic responses of hypocotyls under the control of ARF7 and ARF19
Because our study and other previous studies have shown that the SAUR19 subfamily genes are mainly expressed in the hypocotyls and promote hypocotyl elongation (Spartz et al, 2012; Sun et al, 2016), we selected Arabidopsis SAUR19 subfamily genes for further study

Summary

Introduction

Gravity and light are two of the most important environmental factors affecting the growth and development of plants at multiple stages (Morita and Tasaka, 2005; Whippo and Hangarter, 2006). A typical example of this environmental adaptability is bending growth to react to changes in the direction of gravity (gravitropism) or light (phototropism) (Fankhauser and Christie, 2015; Holland et al, 2009; Masson et al, 2002; Vandenbrink et al, 2014; Whippo and Hangarter, 2006). In Arabidopsis, several components of the auxin signaling pathway have been shown to play roles in tropism, including ARF7, ARF19, IAA19, and IAA29 (Okushima et al, 2005; Sun et al, 2013). The target genes of ARF7/19 may play roles in organ-specific tropic responses

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