DRIF1 and SORTING NEXIN 1 regulate membrane protein homeostasis in Arabidopsis

Zhu et al. explored the function of DRIF1 as a FREE1 suppressor in Arabidopsis. The Plant Cell (2023).

https://doi.org/10.1093/plcell/koad227

By Ying Zhu¹, Jinbo Shen⁴ and Liwen Jiang^1,2,3

¹School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China.

²Institute of Plant Molecular Biology and Agricultural Biotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, China.

³CUHK Shenzhen Research Institute, Shenzhen 518057, China.

⁴State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Hangzhou 311300, China.

Background: Cells maintain the balance and stability of membrane proteins through vacuolar degradation and recycling, which is crucial for plant growth and interactions with the environment. Previously we characterized an endosomal sorting complex required for transport (ESCRT) protein called FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1) in Arabidopsis thaliana. FREE1 performs multiple functions in plant cells, such as regulation of organelle biogenesis and vacuolar degradation of membrane proteins. Via a forward genetic screening approach using the FREE1-RNAi mutant line, we recently identified and characterized two suppressor of free1 (sof) mutants with causal genes called BRO1-DOMAIN PROTEIN AS FREE1 SUPPRESSOR (BRAF) and RESURRECTION1 (RST1).

Questions: What are the underlying mechanisms and regulators of FREE1-mediated functions in plants?

Findings: In this genetic screen, we further identified two sof mutants, sof10 and sof641. These mutants had mutations in a protein called DEAH AND RING DOMAIN-CONTAINING PROTEIN AS FREE1 SUPPRESSOR 1 (DRIF1). We showed that DRIF1 has a close homolog, DRIF2, in the Arabidopsis genome. The embryos of drif1 drif2 double mutants arrested at the globular stage and formed enlarged multivesicular bodies with increased numbers of intraluminal vesicles. DRIF1 coordinates with SORTING NEXIN 1 to regulate PIN-FORMED2 recycling to the plasma membrane. Overall, through a combination of cellular, biochemical, and genetic approaches, our study revealed DRIF1 functions in orchestrating FREE1-mediated intraluminal vesicle formation of multivesicular bodies and vacuolar sorting of membrane proteins for degradation in plants.Next steps: Future studies will aim to understand the mechanisms underlying the formation of enlarged multivesicular bodies with increased intraluminal vesicles in drif1 drif2 double mutants, and how DRIF regulate SORTING NEXIN 1-dependent membrane protein recycling to the plasma membrane in response to multiple environmental cues.

Reference:

Ying Zhu, Qiong Zhao, Wenhan Cao, Shuxian Huang, Changyang Ji, Wenxin Zhang, Marco Trujillo, Jinbo Shen, Liwen Jiang. (2023). The plant-unique DRIF1 regulates membrane protein homeostasis in coordination with SNX1. https://doi.org/10.1093/plcell/koad227