Germin-like protein 1 interacts with proteasome regulator 1 to regulate auxin signaling by controlling Aux/IAA homeostasis
Faqing Xu,
Yongqiang Yu,
Bin Guan,
Tongda Xu,
Zhihong Xu,
Hongwei Xue
Affiliations
Faqing Xu
National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China
Yongqiang Yu
Horticulture and Metabolic Biology Center, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
Bin Guan
Shanghai Collaborative Innovation Center of Agri-Seeds, Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China; Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
Tongda Xu
Horticulture and Metabolic Biology Center, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
Zhihong Xu
National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China
Hongwei Xue
Shanghai Collaborative Innovation Center of Agri-Seeds, Joint Center for Single Cell Biology, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China; Guangdong Laboratory for Lingnan Modern Agriculture, Guangdong Basic Research Center of Excellence for Precise Breeding of Future Crops, College of Agriculture, South China Agricultural University, Guangzhou 510642, China; Corresponding author
Summary: Auxin regulates various aspects of plant growth and development by modulating the transcription of target genes through the degradation of auxin/indole-3-acetic acid (Aux/IAA) repressors via the 26S proteasome. Proteasome regulator 1 (PTRE1), a positive regulator of proteasome activity, has been implicated in auxin-mediated proteasome suppression; however, the mechanism by which auxin modulates PTRE1 function remains unclear. Here, we demonstrate that auxin promotes the interaction between germin-like protein 1 (GLP1) and PTRE1, facilitating PTRE1 retention at the plasma membrane. The relocation of PTRE1 results in reduced nuclear 26S proteasome activity, and thus the attenuated Aux/IAA degradation and altered Aux/IAA homeostasis, ultimately resulting in suppressed auxin-mediated transcriptional regulation. Our findings uncover a previously uncharacterized regulatory axis in auxin signaling that controls Aux/IAA protein stability, functioning alongside the TIR1- and TRANSMEMBRANE KINASE 1 (TMK1)-mediated pathways, and highlight the coordination of auxin signaling from the cell surface to the nucleus via auxin-induced PTRE1 relocation, which fine-tunes Aux/IAA protein homeostasis and auxin responses.
