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OsNHX5-mediated pH homeostasis is required for post-Golgi trafficking of seed storage proteins in rice endosperm cells.

ABSTRACT: BACKGROUND:As the major storage protein in rice seeds, glutelins are synthesized at the endoplasmic reticulum (ER) as proglutelins and transported to protein storage vacuoles (PSVs) called PBIIs (Protein body IIs), where they are cleaved into mature forms by the vacuolar processing enzymes. However, the molecular mechanisms underlying glutelin trafficking are largely unknown. RESULTS:In this study, we report a rice mutant, named glutelin precursor accumulation6 (gpa6), which abnormally accumulates massive proglutelins. Cytological analyses revealed that in gpa6 endosperm cells, proglutelins were mis-sorted, leading to the presence of dense vesicles (DVs) and the formation paramural bodies (PMBs) at the apoplast, consequently, smaller PBII were observed. Mutated gene in gpa6 was found to encode a Na+/H+ antiporter, OsNHX5. OsNHX5 is expressed in all tissues analyzed, and its expression level is much higher than its closest paralog OsNHX6. The OsNHX5 protein colocalizes to the Golgi, the trans-Golgi network (TGN) and the pre-vacuolar compartment (PVC) in tobacco leaf epidermal cells. In vivo pH measurements indicated that the lumens of Golgi, TGN and PVC became more acidic in gpa6. CONCLUSIONS:Our results demonstrated an important role of OsNHX5 in regulating endomembrane luminal pH, which is essential for seed storage protein trafficking in rice.

SUBMITTER: Zhu J

PROVIDER: S-EPMC6612104 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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OsNHX5-mediated pH homeostasis is required for post-Golgi trafficking of seed storage proteins in rice endosperm cells.

Zhu Jianping J Ren Yulong Y Wang Yunlong Y Liu Feng F Teng Xuan X Zhang Yuanyan Y Duan Erchao E Wu Mingming M Zhong Mingsheng M Hao Yuanyuan Y Zhu Xiaopin X Lei Jie J Wang Yongfei Y Yu Yanfang Y Pan Tian T Bao Yiqun Y Wang Yihua Y Wan Jianmin J

BMC plant biology 20190705 1

<h4>Background</h4>As the major storage protein in rice seeds, glutelins are synthesized at the endoplasmic reticulum (ER) as proglutelins and transported to protein storage vacuoles (PSVs) called PBIIs (Protein body IIs), where they are cleaved into mature forms by the vacuolar processing enzymes. However, the molecular mechanisms underlying glutelin trafficking are largely unknown.<h4>Results</h4>In this study, we report a rice mutant, named glutelin precursor accumulation6 (gpa6), which abnor ...[more]

PMID: 31277576

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Project description:BackgroundRice is not only an essential food but also a source of high quality protein. Polyploidy is an evolutionary trajectory in plants, and enhancing glutelin by polyploidization is an attractive strategy for improving the nutritional value of rice seeds and presents a great potential for enhancing the commercial value of rice. Elucidating the mechanisms underlying glutelin synthesis and accumulation in tetraploid rice is of great significance.ResultsTo enhance the nutritional value of rice, we developed tetraploid rice and evaluated the contents of various nutrient elements in mature seeds. The results revealed a significant increase in protein contents, including the total seed storage proteins, glutelins, and amino acids in tetraploid rice when compared with those in diploid rice. Tandem mass tag-based quantitative proteomic analyses of seeds revealed that glutelins regulated by several glutelin genes in 9311-4x were significantly up-regulated (≥1.5-fold), which was further verified by immunoblot analyses. In addition, temporal expression patterns of various glutelin subunits in different rice lines were investigated. The results revealed significant differences in the expression patterns between diploid and tetraploid rice seeds. Cytohistological analyses results revealed that the thickness of aleurone cell layers increased significantly by 32% in tetraploid rice, the structures of protein storage vacuoles (PSVs) in sub-aleurone cells were more diverse and abundant than those of diploid rice. Temporal expression and proteomic analyses results revealed that protein disulfide isomerase-like 1-1 expression levels were higher in tetraploid rice than in diploid rice, and that the gene responded to oxidative folding with increased levels of proglutelin and appropriate distribution of seed glutelins in tetraploid rice.ConclusionThe results of the present study revealed that polyploidization increased glutelin content by influencing glutelin biosynthesis, transport, and deposition, while variations in glutelin accumulation between tetraploid and diploid rice were largely manifested in the initial time, duration, and relative levels of various glutelin gene expressions during seed filling stages. These findings provide novel insights into improving the protein quality and nutritional value of rice seeds by polyploid breeding.

Dataset Information

OsNHX5-mediated pH homeostasis is required for post-Golgi trafficking of seed storage proteins in rice endosperm cells.

Publications

OsNHX5-mediated pH homeostasis is required for post-Golgi trafficking of seed storage proteins in rice endosperm cells.

Similar Datasets

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