Biology subjects

Lung, H.-F.

Publications and source records attributed to Lung, H.-F..

3 recordsLinked to original sources

bioRxiv2025

Involvement of PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1 in COPII assembly by interacting with SAR1 GTPase

Inorganic phosphate (Pi) uptake and translocation are crucial for plant growth and development, relying on plasma membrane targeting of PHOSPHATE TRANSPORTER1 (PHT1) transporters. The plant-specific endoplasmic reticulum (ER)-resident PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1 (PHF1) is structurally related to SEC12, which initiates the coat protein complex II (COPII) assembly as a guanine nucleotide exchange factor (GEF) by activating the small GTPase SAR1. In contrast, PHF1 loses the conserved catalytic residues critical for GEF activity and specifically assists the ER exit of the PHT1 transporters. However, the underlying molecular mechanism remains unknown. In this study, we showed that overexpression of Arabidopsis thaliana PHT1;1 (AtPHT1;1) in the tobacco transient expression system caused a portion of AtPHF1 distribution into AtSAR1b- and AtSEC24a-labeled ER exit sites. We demonstrated that AtPHF1 interacts with AtSAR1b and AtSAR1c based on the tripartite split-GFP association in agro-infiltrated tobacco leaves and verified this interaction using miniTurbo-based proximity labeling. We also confirmed its physiological relevance by co-immunoprecipitation of the endogenous AtPHF1 with AtSAR1c-GFP in Arabidopsis transgenic lines. Importantly, AtPHF1 preferentially interacts with the GDP-locked AtSAR1. Therefore, we propose that AtPHF1 or the AtPHT1;1-AtPHF1 complex interacts with the SAR1 GTPase to participate in the early step of COPII recruitment for the ER export of PHT1 transporters.

plant biology↗

bioRxiv2024

CORNICHON HOMOLOG 5-dependent ER export of membrane cargoes in phosphate-starved Arabidopsis root as revealed by membrane proteomic analysis

Developing plants tolerant of low phosphate (Pi) availability is essential to reduce reliance on fertilizers and achieve agricultural sustainability. One strategy is to enhance the endoplasmic reticulum (ER) export of cargoes associated with Pi starvation and their trafficking to final destinations. However, the mechanisms underlying this process are underexplored. We recently discovered that Arabidopsis thaliana CORNICHON HOMOLOG 5 (AtCNIH5) encodes a Pi deficiency-induced ER cargo receptor that regulates Pi homeostasis. To find potential membrane cargoes of AtCNIH5, we applied the UV-cleavable 4-hexylphenylazosulfonate (Azo)-solubilized microsomal protein extraction for iTRAQ-based proteomic analysis. We identified 4,317 proteins in Pi-limited Arabidopsis roots, with 372 upregulated and 106 downregulated proteins in cnih5. Besides PHOSPHATE TRANSPORTER 1 proteins (PHT1s), downregulation of the biosynthetic or modifying enzymes for cell wall polysaccharides, very long-chain fatty acids, and their derivative extracellular aliphatic compounds is over-represented. Using the yeast split-ubiquitin and the in-planta tripartite split-GFP assays, we verified the interaction of AtCNIH5 with various downregulated transporters in cnih5, including AtPHT1s, AtOCT1, AtURGT6, AtDTX21, and AtDTX35. In addition, we demonstrated that the C-terminal acidic residue of AtCNIH5 is required for interaction with AtOCT1 but not with AtPHT1;1 or AtDTX21, indicating distinct cargo selection mechanisms. More importantly, enhancing in-situ AtCNIH5 expression/activity enhances plant growth. By analogy with transcriptional factors that govern gene expression, we propose that AtCNIH5 acts as a low Pi-responsive hub to facilitate ER export of specific membrane cargoes, providing a potential engineering strategy to improve plant fitness under suboptimal Pi supply.

plant biology↗

bioRxiv2024

Phosphate Starvation-Induced CORNICHON HOMOLOG 5 as Endoplasmic Reticulum Cargo Receptor for PHT1 Transporters in Arabidopsis

Inorganic phosphate (Pi) is essential for plant growth and is acquired and distributed by the plasma membrane PHOSPHATE TRANSPORTER 1 proteins (PHT1s). Enhancing the abundance of PHT1s at the cell surface thus ensures plant productivity and sustainable agriculture. CORNICHON HOMOLOG proteins (CNIHs) are conserved eukaryotic cargo receptors that mediate the selective endoplasmic reticulum (ER) export of membrane proteins. In this study, we identified the Arabidopsis thaliana CNIH5 (AtCNIH5) as a Pi starvation-inducible gene, preferentially expressed in vascular tissues and outer root cell layers above the meristem. AtCNIH5 co-localizes to the AtSAR1A/AtSEC16A/AtSEC24A-labeled ER exit sites and interacts with AtPHT1;1. Loss of AtCNIH5 confers reduced shoot Pi levels under Pi sufficiency due to the reduced translocation of Pi from roots to shoots, as well as decreased Pi uptake under Pi deficiency. The cnih5 mutant exhibits decreased abundance of AtPHT1s but increased PHOSPHATE TRANSPORTER TRAFFIC FACILITATOR1 (AtPHF1), which enables the ER exit of PHT1s. The cnih5 mutant also shows a lower plasma membrane targeting efficiency of split-GFP tagged-AtPHT1;1 in the root hair and the epidermis within the root transition/elongation zone. Consistently, dysfunctional AtCNIH5 exerts a suppressive effect on the growth of phf1 and alleviates Pi toxicity in the Pi overaccumulator pho2. However, the in vivo protein-protein interaction and degradation assays indicated that AtCNIH5 is not a direct target of AtPHO2. Our findings unveil that AtCNIH5 is a low Pi-responsive ER cargo receptor that interplays with AtPHF1 to promote the plasma membrane targeting of AtPHT1s in a cell-type-dependent manner.

plant biology↗