Plastidial Starch Phosphorylase in Sweet Potato Roots Is Proteolytically Modified by Protein-Protein Interaction with the 20S Proteasome

Lin, Yichen; Chen, Han-Min; Chou, I-Min; Chen, An-Na; Chen, Chia-Pei; Young, Guang-Huar; Lin, Chi‐Tsai; Cheng, Chiung-Hsiang; Chang, Shih‐Chung; Juang, Rong-Huay

doi:10.1371/journal.pone.0035336

Cited by 16 publications

(18 citation statements)

References 65 publications

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“…The 20S core particle was shown to have basal proteolytic activity toward unstructured or oxidized proteins (60). It is also implicated in maturation and specific cleavage of various proteins, which gain access to the proteolytic chamber through an interaction with N termini of the ␣-subunits (8,49). In the PPC of heterokontophytes, we identified proteasomal subunits of the 20S core particle, including proteolytic active subunits.…”

Section: Figmentioning

confidence: 94%

Distribution of the SELMA Translocon in Secondary Plastids of Red Algal Origin and Predicted Uncoupling of Ubiquitin-Dependent Translocation from Degradation

et al. 2012

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cProtein import into complex plastids of red algal origin is a multistep process including translocons of different evolutionary origins. The symbiont-derived ERAD-like machinery (SELMA), shown to be of red algal origin, is proposed to be the transport system for preprotein import across the periplastidal membrane of heterokontophytes, haptophytes, cryptophytes, and apicomplexans. In contrast to the canonical endoplasmic reticulum-associated degradation (ERAD) system, SELMA translocation is suggested to be uncoupled from proteasomal degradation. We investigated the distribution of known and newly identified SELMA components in organisms with complex plastids of red algal origin by intensive data mining, thereby defining a set of core components present in all examined organisms. These include putative pore-forming components, a ubiquitylation machinery, as well as a Cdc48 complex. Furthermore, the set of known 20S proteasomal components in the periplastidal compartment (PPC) of diatoms was expanded. These newly identified putative SELMA components, as well as proteasomal subunits, were in vivo localized as PPC proteins in the diatom Phaeodactylum tricornutum. The presented data allow us to speculate about the specific features of SELMA translocation in contrast to the canonical ERAD system, especially the uncoupling of translocation from degradation.O rganelles such as plastids, including those of secondary origin, almost completely rely on protein import from the host cytosol (46, 65). The structure of complex plastids, surrounded by three or four membranes required, in contrast to primary plastids, the evolution of several additional protein transport mechanisms. Complex plastids arose through secondary endosymbiosis, a process which describes the engulfment of a former free-living eukaryotic alga into a eukaryotic host cell (32, 33). During evolution, the symbiont was subsequently reduced in terms of compartmentalization and genome size to an organelle strictly dependent on the host cell (16,32). Different types of secondary plastids exist in a very broad range of algae and protists, which can be distinguished based on their evolutionary origin (e.g., a red or green alga derived symbiont), as well as on the amount of cellular reduction inside the host cell. Our understanding of the evolution of organisms harboring a secondary plastid of red algal origin has changed in the last few years. According to the chromalveolate hypothesis, six major lineages were grouped together to be of monophyletic origin: cryptophytes, haptophytes, heterokontophytes, peridinincontaining dinoflagellates, apicomplexans, and the non-plastidcontaining ciliates, as well as several smaller lineages related to some chromalveolate members (15, 41). However, recent phylogenetic analyses have given rise to extended theories about the evolution of the lineages with a red algal endosymbiont, including serial endosymbiotic events with secondary, as well as tertiary, endosymbioses (21,22,26,27,56,61,71,75).It has been shown that the lineages wi...

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Section: Figmentioning

confidence: 94%

Distribution of the SELMA Translocon in Secondary Plastids of Red Algal Origin and Predicted Uncoupling of Ubiquitin-Dependent Translocation from Degradation

et al. 2012

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“…It has also been suggested that L80 is not important for regulation of the enzyme but, instead, protects the OsPho1 protein under heat stress conditions (4). In sweet potato roots, high molecular weight complexes showing Pho1 activity contained the 20S proteasome that interacts with the L78 region of Pho1 and degrades the Pho1 protein under heat stress (10). In addition, like the L80 of OsPho1 the L78 of sweet potato, Pho1 has a number of charged amino acids that have been suggested to be potential targets for protein kinase activity (11).…”

mentioning

confidence: 99%

Rice Endosperm Starch Phosphorylase (Pho1) Assembles with Disproportionating Enzyme (Dpe1) to Form a Protein Complex That Enhances Synthesis of Malto-oligosaccharides

Hwang

Koper

Satoh

et al. 2016

Journal of Biological Chemistry

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Starch synthesis in cereal grain endosperm is dependent on the concerted actions of many enzymes. The starch plastidial phosphorylase (Pho1) plays an important role in the initiation of starch synthesis and in the maturation of starch granule in developing rice seeds. Prior evidence has suggested that the rice enzyme, OsPho1, may have a physical/functional interaction with other starch biosynthetic enzymes. Pulldown experiments showed that OsPho1 as well as OsPho1 devoid of its L80 region, a peptide unique to higher plant phosphorylases, captures disproportionating enzyme (OsDpe1). Interaction of the latter enzyme form with OsDpe1 indicates that the putative regulatory L80 is not responsible for multienzyme assembly. This heterotypic enzyme complex, determined at a molar ratio of 1:1, was validated by reciprocal co-immunoprecipitation studies of native seed proteins and by co-elution chromatographic and comigration electrophoretic patterns of these enzymes in rice seed extracts. The OsPho1-OsDpe1 complex utilized a broader range of substrates for enhanced synthesis of larger maltooligosaccharides than each individual enzyme and significantly elevated the substrate affinities of OsPho1 at 30°C. Moreover, the assembly with OsDpe1 enables OsPho1 to utilize products of transglycosylation reactions involving G1 and G3, sugars that it cannot catalyze directly.

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“…This insert is believed to have evolved from an intron (Camirand et al, 1990), and it sterically prevents the binding of plastidial phosphorylases to large, highly branched polysaccharides (Young et al, 2006). Research in sweetpotato roots has showed that the 20S proteasome interacted with plastidial phosphorylase through its L78 insert and further degraded the plastidial phosphorylase under heat stress conditions (Lin et al, 2012), indicating that the L78 insert acts as a regulatory element for phosphorylase activity.…”

Section: Resultsmentioning

confidence: 99%

Phylogenetic Analysis and Expression Profiles of Starch Phosphorylase Family Genes in Cassava under Diverse Environments

et al. 2018

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Starch phosphorylase (Pho), especially the plastidial type, plays an important role in starch biosynthesis. The availability of a complete cassava (Manihot esculenta Crantz) genome database allowed the identification of five Pho family members, which could be grouped into the plastidial type (MePho1a, MePho1b, and MePho1c) and cytosolic type (MePho2 and MePho3) on the basis of phylogenetic analysis. Spatial gene expression analysis of various cassava tissues revealed that plastidial MePho1b had the highest transcriptional activity in root stele, whereas the cytosolic MePho2 was expressed with higher levels in leaves and petiole. Spatial expression analysis showed that MePho1b was strongly expressed in the tuber during root development process, especially at 70 and 180 d after planting, whereas MePho1a had highest expression in leaves at 180 d after planting. Expression of MePho1b and MePho2 could be induced by salt, drought, exogenous abscisic acid, methyl jasmonate, and salicylic acid signal in the leaves of abiotic stress‐treated plantlets. In addition, the expression profiles of MePho1b and starch branching enzyme gene member MeSBE2.2 exhibited significant correlation under diverse stress environments, indicating that they may have coordinated functions.

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Plastidial Starch Phosphorylase in Sweet Potato Roots Is Proteolytically Modified by Protein-Protein Interaction with the 20S Proteasome

Cited by 16 publications

References 65 publications

Distribution of the SELMA Translocon in Secondary Plastids of Red Algal Origin and Predicted Uncoupling of Ubiquitin-Dependent Translocation from Degradation

Distribution of the SELMA Translocon in Secondary Plastids of Red Algal Origin and Predicted Uncoupling of Ubiquitin-Dependent Translocation from Degradation

Rice Endosperm Starch Phosphorylase (Pho1) Assembles with Disproportionating Enzyme (Dpe1) to Form a Protein Complex That Enhances Synthesis of Malto-oligosaccharides

Phylogenetic Analysis and Expression Profiles of Starch Phosphorylase Family Genes in Cassava under Diverse Environments

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