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Scientists find essential roles of VPS28 in auxin-mediated plant development
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The highly conserved ESCRT pathway plays critical roles in endosomal sorting of ubiquitinated plasma membrane proteins for degradation. However, the functions of many components of the ESCRT machinery in plants remain unsolved. Recently, Youfa Cheng’s group at the Institute of Botany, Chinese Academy of Sciences (IBCAS) show that the ESCRT-I subunits VPS28A and VPS28B are functionally redundant and required for embryo development in Arabidopsis.

The scientists conducted a genetic screen and isolated pid ncp104 double mutants, which failed to develop cotyledons. They further identified that mutations in PID and VPS28A caused the phenotypes. In the ncp104 mutant, the Glu194 of the ESCRT-I subunit VPS28A changed to Lys (VPS28AE194K). Surprisingly, the loss-of-function vps28a mutant plants were similar to wild type plants. The researchers discovered that ncp104 was a rare recessive gain-of-function allele of vps28a. Similar recessive gain-of-function mutant behavior was observed in the u506 allele of the C. elegans deg-1 gene. deg-1 encodes a subunit of a sodium channel.

They further found that single vps28a and vps28b loss-of-function mutants did not display obvious developmental defects, but the double mutants showed abnormal cell division patterns and were arrested at the globular embryo stage. The vps28a vps28b double mutants showed altered auxin responses, disrupted PIN1-GFP expression patterns and abnormal PIN1-GFP accumulation in small aberrant vacuoles. The ncp104 mutation may cause the VPS28A protein unstable and/or toxic. The results demonstrate that the ESCRT-I components VPS28A and VPS28B redundantly play essential roles in vacuole formation, endosomal sorting of plasma membrane proteins and auxin-mediated plant development.

The work provides new insights for understanding the functions of VPS28 in plants, and a unique and rare material. It was supported by the funds from the National Natural Science Foundation of China and the Ministry of Science and Technology of China.

The paper was online published in The Plant Journal on October 15th, 2020, entitled “The ESCRT-I components VPS28A and VPS28B are essential for auxin-mediated plant development”. The graduate students Jianyang Liu and Yanning Wang are the co-first authors, and Youfa Cheng the corresponding author.

 ncp104 is a rare recessive gain-of-function allele of vps28a.


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