AtNHX5 and AtNHX6 Are Required for the Subcellular Localization of the SNARE Complex That Mediates the Trafficking of Seed Storage Proteins in Arabidopsis.

Xuexia Wu,Kazuo Ebine,Takashi Ueda,Quan-Sheng Qiu

doi:10.1371/journal.pone.0151658

Xuexia Wu, Kazuo Ebine + Show 2 more

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https://doi.org/10.1371/journal.pone.0151658

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Abstract

The SNARE complex composed of VAMP727, SYP22, VTI11 and SYP51 is critical for protein trafficking and PSV biogenesis in Arabidopsis. This SNARE complex directs the fusion between the prevacuolar compartment (PVC) and the vacuole, and thus mediates protein trafficking to the vacuole. In this study, we examined the role of AtNHX5 and AtNHX6 in regulating this SNARE complex and its function in protein trafficking. We found that AtNHX5 and AtNHX6 were required for seed production, protein trafficking and PSV biogenesis. We further found that the nhx5 nhx6 syp22 triple mutant showed severe defects in seedling growth and seed development. The triple mutant had short siliques and reduced seed sets, but larger seeds. In addition, the triple mutant had numerous smaller protein storage vacuoles (PSVs) and accumulated precursors of the seed storage proteins in seeds. The PVC localization of SYP22 and VAMP727 was repressed in nhx5 nhx6, while a significant amount of SYP22 and VAMP727 was trapped in the Golgi or TGN in nhx5 nhx6. AtNHX5 and AtNHX6 were co-localized with SYP22 and VAMP727. Three conserved acidic residues, D164, E188, and D193 in AtNHX5 and D165, E189, and D194 in AtNHX6, were essential for the transport of the storage proteins, indicating the importance of exchange activity in protein transport. AtNHX5 or AtNHX6 did not interact physically with the SNARE complex. Taken together, AtNHX5 and AtNHX6 are required for the PVC localization of the SNARE complex and hence its function in protein transport. AtNHX5 and AtNHX6 may regulate the subcellular localization of the SNARE complex by their transport activity.

Highlights

Seeds of crop plants are the principle source of proteins for humans and livestock [1,2,3]
These results indicate that AtNHX5 and AtNHX6 are involved in seed production, protein trafficking and protein storage vacuoles (PSVs) biogenesis, which are similar to what Reguera et al (2015) had reported [39]
Both Reguera et al (2015) and our results demonstrate that AtNHX5 and AtNHX6 are required for the transport of the seed storage proteins into the PSVs as well as the biogenesis of the PSVs in Arabidopsis [39]

Summary

Introduction

Seeds of crop plants are the principle source of proteins for humans and livestock [1,2,3]. Seed storage proteins are primarily accumulated in the protein storage vacuoles (PSVs) [4,5,6,7]. AtNHX5 and AtNHX6 and Seed Storage Protein Trafficking. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

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