Phytochelatin Synthase has Contrasting Effects on Cadmium and Arsenic Accumulation in Rice Grains

Uraguchi, Shimpei; Tanaka, Nobuhiro; Hofmann, Christian; Abiko, Kaho; Ohkama‐Ohtsu, Naoko; Weber, Michael; Kamiya, Takehiro; Sone, Yuka; Nakamura, Ryosuke; Takanezawa, Yasukazu; Kiyono, Masako; Fujiwara, Toru; Clemens, Stephan

doi:10.1093/pcp/pcx114

Cited by 91 publications

(50 citation statements)

References 56 publications

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“…2), which are known to play a critical role in the detoxification of Cd via complexation of the toxic ion (Cobbett & Goldsbrough, 2002). Mutation of PC synthase genes in Arabidopsis and rice leads to hypersensitivity to Cd (Howden et al, 1995b;Uraguchi et al, 2017), whereas overexpression of PC synthase genes or the activation of the GSH-dependent pathway can enhance Cd tolerance (Brunetti et al, 2011;Chen et al, 2015Chen et al, , 2016. Increased Cd accumulation in the roots of cadt1 (Fig.…”

Section: Discussionmentioning

confidence: 99%

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Mutation in OsCADT1 enhances cadmium tolerance and enriches selenium in rice grain

et al. 2020

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Summary How cadmium (Cd) tolerance in rice is regulated remains poorly understood. We used a forward genetic approach to investigate Cd tolerance in rice. Using a root elongation assay, we isolated a rice mutant with enhanced Cd tolerance, cadt1, from an ethyl methanesulphonate (EMS)‐mutagenized population of a widely grown Indica cultivar. The mutant accumulated more Cd in roots but not in shoots and grains. Using genomic resequencing and complementation, we identified OsCADT1 as the causal gene for the mutant phenotype, which encodes a putative serine hydroxymethyltransferase. OsCADT1 protein was localized to the nucleus and the OsCADT1 gene was expressed in both roots and shoots. OsCADT1 mutation resulted in higher sulphur and selenium accumulation in the shoots and grains. Selenate influx in cadt1 was 2.4 times that of the wild‐type. The mutant showed higher expression of the sulphate/selenate transporter gene OsSULTR1;1 and the sulphur‐deficiency‐inducible gene OsSDI1. Thiol compounds including cysteine, glutathione and phytochelatins were significantly increased in the mutant, underlying its increased Cd tolerance. Growth and grain biomass were little affected. The results suggest that OsCADT1 acts as a negative regulator of sulphate/selenate uptake and assimilation. OsCADT1 mutation increases Cd tolerance and enriches selenium in rice grains, providing a novel solution for selenium biofortification.

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Section: Discussionmentioning

confidence: 99%

“…Both the Arabidopsis thaliana GSH‐ and PC‐deficient mutants are highly sensitive to Cd (Howden et al , 1995a,b). The rice PCS1 mutants are also more sensitive to Cd (Uraguchi et al , ). Treatments of plant roots with buthionine‐sulphoximine, an inhibitor of GSH synthesis, also caused Cd sensitivity (Cobbett et al , ).…”

Section: Introductionmentioning

confidence: 99%

Mutation in OsCADT1 enhances cadmium tolerance and enriches selenium in rice grain

et al. 2020

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“…In a recent study, Uraguchi et al. () also isolated additional OsPCS2 variants, which were designated as OsPCS1 variants in their article, having a different transcription start site, and they reported that the longest OsPCS2 variant, OsPCS1full , showed the highest abundance among OsPCS transcripts. In contrast, Das et al.…”

Section: Discussionmentioning

confidence: 99%

“…Similar phenotypes were observed for other mutants involved in PC synthesis and transport. Recently, it was reported that the T‐DNA mutant of OsPCS2 showed a weak phenotype under Cd stress, in contrast to a clear decrease in As tolerance (Uraguchi et al., ). In addition, the knockout of OsABCC1 did not affect Cd toxicity in rice (Song et al., ), in contrast to Arabidopsis atabcc1 atabcc2 mutant showing high sensitivity to As and Cd (Park et al., ; Song et al., ).…”

Section: Discussionmentioning

confidence: 99%

Rice phytochelatin synthases OsPCS1 and OsPCS2 make different contributions to cadmium and arsenic tolerance

et al. 2018

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Cadmium (Cd) and arsenic (As) pollution in paddy soil and their accumulation in rice (Oryza sativa) pose serious threats to human health. Rice internally detoxifies these toxic metal and metalloid to some extent, resulting in their accumulation within the edible parts. However, the mechanisms of Cd and As detoxification in rice have been poorly elucidated. Plants synthesize thiol-rich metal-chelating peptides, termed phytochelatins (PCs). We characterized rice PC synthase (PCS) and investigated its contribution to Cd and As tolerance in rice. We identified two PCS homolog genes, OsPCS1 and OsPCS2, in the rice genome. The expression of OsPCS1 was upregulated by As(III) stress in the roots but that of OsPCS2 was not significantly affected.The expression level of OsPCS2 was higher than that of OsPCS1 in the shoots and roots. Recombinant OsPCS1 and OsPCS2 proteins differed in their metal activation.OsPCS1 was more strongly activated by As(III) than by Cd; however, OsPCS2 was more strongly activated by Cd than by As(III). Genetically engineered plants having their OsPCS2 expression silenced via RNA interference (OsPCS2 RNAi) contained less PCs and more glutathione (GSH), a substrate of PC synthesis, than wild-type plants, although there was no significant difference in OsPCS1 RNAi plants. OsPCS2 RNAi plants were sensitive to As(III) stress, but Cd tolerance was little affected. On the other hand, treatment with buthionine sulfoximine, an inhibitor of GSH biosynthesis, significantly decreased Cd and As tolerance of rice seedlings. These findings indicate that OsPCS2 is a major isozyme controlling PC synthesis, and that PCs are important for As tolerance in rice. However, PC synthesis may make a smaller contribution to Cd tolerance in rice, and GSH plays crucial roles, not only as a substrate of PC synthesis.

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“…A recent study reported alternatively spliced transcripts of rice OsPCS2 gene to be involved in alleviation of Cd and As stresses in a tissue-specific way [62]. In another recent work, four rice OsPCS1 transcript variants and one OsPCS2 were isolated and their expression in PCS-deficient Arabidopsis and Schizosaccharomyces pombe mutants revealed PCS activity in response to Cd and As in the longest PCS1 variant, OsPCS1full [63]. In this regard, it was quite possible that the evolutionary forces could attribute exon-intron variations between monocot and dicot species.…”

Section: Sequence Analysis Of Pcssmentioning

confidence: 97%

Comparative analyses of phytochelatin synthase (PCS) genes in higher plants

Filiz

Saracoglu

Özyiğit

et al. 2019

Biotechnology & Biotechnological Equipment

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Plants employ various defence strategies to ameliorate the effects of heavy metal exposures, leading to re-establishment of metal homeostasis. One of the strategies includes the biosynthesis of main heavy metal detoxifying peptides phytochelatins (PCs) by phytochelatin synthase (PCS). In the present study, 14 PCS homologues were identified in the genomes of 10 selected plants. The size of these PCSs was 452-545 amino acid residues, with characteristic phytochelatin and phytochelatin_C domains. The N-terminal site of the proteins is highly conserved, whereas the C-terminal site is less conserved. Further, the present study also identified fully conserved Cys residues involved in heavy metal binding reported earlier. In addition, other preserved cysteines, with minor substitutions Cys(C)!Ser(S) or Tyr(Y) or Trp(W), were also identified in the PCS sequences that might be associated with metal binding. The reported catalytic triad residues from Arabidopsis, Cys56, His162 and Asp180, are all conserved at the respective sites of PCSs. A clear monocot/dicot separation was revealed by phylogenetic analysis and was further corroborated by the exon-intron organisations of the PCS genes. Moreover, gene ontology terms, coexpression network, cis-regulatory motif and miRNA analyses indicated that the complex as well as dynamic regulation of PCSs has significant involvement in different metabolic pathways associated with signalling, defence, stress and phytohormone, in addition to metal detoxification. Moreover, variations in protein structure are suggested to confer the functional divergence in PCS proteins.

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Phytochelatin Synthase has Contrasting Effects on Cadmium and Arsenic Accumulation in Rice Grains

Cited by 91 publications

References 56 publications

Mutation in OsCADT1 enhances cadmium tolerance and enriches selenium in rice grain

Mutation in OsCADT1 enhances cadmium tolerance and enriches selenium in rice grain

Rice phytochelatin synthases OsPCS1 and OsPCS2 make different contributions to cadmium and arsenic tolerance

Comparative analyses of phytochelatin synthase (PCS) genes in higher plants

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