Increased salt and drought tolerance by D-pinitol production in transgenic Arabidopsis thaliana

Ahn, Curie; Park, Uhnmee; Park, Phun Bum

doi:10.1016/j.bbrc.2018.08.183

Cited by 34 publications

(23 citation statements)

References 31 publications

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“…The reaction mechanism presented here is analogous to the one described by Ruis and Hoffmann‐Ostenhof () for the epimerase from Trifolium incarnatum and is different to that demonstrated for the epimerase identified by Ahn et al . () in soybean. Therefore, it appears that two different pathways for epimerization of d ‐ononitol to d ‐pinitol may exist in legumes.…”

Section: Discussionmentioning

confidence: 99%

“…By searching Soybase and NCBI EST databases for drought‐induced epimerases in soybean, Ahn et al . () identified a single NAD + ‐dependent epimerase that catalyzed the epimerization of d ‐ononitol to d ‐pinitol in vitro . In this work, we used a different approach for the identification of d ‐ononitol epimerase in Medicago truncatula : first, we identified the gene encoding myo ‐inositol O ‐methyltransferase ( MtIMT ), the enzyme which synthesizes the direct precursor of d ‐pinitol, d ‐ononitol, and subsequently analyzed publicly available microarray data from drought‐stressed plants in order to find genes encoding NAD(P)(H)‐dependent enzymes with expression profile similar to the MtIMT gene.…”

Section: Discussionmentioning

confidence: 99%

“…It was also found that the identified dehydrogenases catalyze epimerization of d ‐ononitol to d ‐pinitol in a two‐step manner similar to the one described by Ruis and Hoffmann‐Ostenhof (), albeit different from the single‐enzyme catalysis reported by Ahn et al . (). We also transformed tobacco plants with MtIMT gene and obtained transformants which produced d ‐ononitol.…”

Section: Introductionmentioning

confidence: 97%

“…Recently, Ahn et al . () showed that epimerization of d ‐ononitol to d ‐pinitol in soybean can be catalyzed by a single 43 kDa NAD + ‐dependent epimerase without the requirement for NADPH, which indicated that there may exist two different pathways for epimerization of d ‐ononitol to d ‐pinitol in legumes.…”

Section: Introductionmentioning

confidence: 99%

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Two‐step d‐ononitol epimerization pathway in Medicago truncatula

2019

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Methylated inositol, D-pinitol (3-O-methyl-D-chiro-inositol), is a common constituent in legumes. It is synthesized from myo-inositol in two reactions: the first reaction, catalyzed by myo-inositol-O-methyltransferase (IMT), consists of a transfer of a methyl group from S-adenosylmethionine to myo-inositol with the formation of D-ononitol, while the second reaction, catalyzed by D-ononitol epimerase (OEP), involves epimerization of D-ononitol to D-pinitol. To identify the genes involved in D-pinitol biosynthesis in a model legume Medicago truncatula, we conducted a BLAST search on its genome using soybean IMT cDNA as a query and found putative IMT (MtIMT) gene. Subsequent co-expression analysis performed on publicly available microarray data revealed two potential OEP genes: MtOEPA, encoding an aldo-keto reductase and MtOEPB, encoding a short-chain dehydrogenase. cDNAs of all three genes were cloned and expressed as recombinant proteins in E. coli. In vitro assays confirmed that putative MtIMT enzyme catalyzes methylation of myo-inositol to D-ononitol and showed that MtOEPA enzyme has NAD + -dependent D-ononitol dehydrogenase activity, while MtOEPB enzyme has NADP + -dependent D-pinitol dehydrogenase activity. Both enzymes are required for epimerization of D-ononitol to D-pinitol, which occurs in the presence of NAD + and NADPH. Introduction of MtIMT, MtOEPA, and MtOEPB genes into tobacco plants resulted in production of D-ononitol and D-pinitol in transformants. As this two-step pathway of D-ononitol epimerization is coupled with a transfer of reducing equivalents from NADPH to NAD + , we speculate that one of the functions of this pathway might be regeneration of NADP + during drought stress.Keywords: carbohydrate metabolism, drought, legumes, Medicago truncatula, metabolic adaptation to stress, metabolic pathways. D-pinitol and drought resistance was also found by Guo and Oosterhuis (1997), who reported that soybean cultivars that showed increased resistance to soil drought accumulated larger quantities of D-pinitol than sensitive varieties.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Two‐step d‐ononitol epimerization pathway in Medicago truncatula

2019

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“…Pinitol has been reported to be involved in plant osmotic adjustment to maintain the metabolic activity under drought stress [38]. Transgenic Arabidopsis overexpressing a biosynthetic enzyme of the pinitol pathway demonstrated enhanced drought and salinity tolerance compared with the wild type [39]. It has been suggested that polyols could prevent oxidative damage, defend membrane integrity, and maintain enzyme activities [12,40].…”

Section: Osmoprotectants In Leavesmentioning

confidence: 99%

Physiological and Biochemical Responses to Salt Stress of Alfalfa Populations Selected for Salinity Tolerance and Grown in Symbiosis with Salt-Tolerant Rhizobium

et al. 2020

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Alfalfa and its rhizobial symbiont are sensitive to salinity. We compared the physiological responses of alfalfa populations inoculated with a salt-tolerant rhizobium strain, exposed to five NaCl concentrations (0, 20, 40, 80, or 160 mM NaCl). Two initial cultivars, Halo (H-TS0) and Bridgeview (B-TS0), and two populations obtained after three cycles of recurrent selection for salt tolerance (H-TS3 and B-TS3) were compared. Biomass, relative water content, carbohydrates, and amino acids concentrations in leaves and nodules were measured. The higher yield of TS3-populations than initial cultivars under salt stress showed the effectiveness of our selection method to improve salinity tolerance. Higher relative root water content in TS3 populations suggests that root osmotic adjustment is one of the mechanisms of salt tolerance. Higher concentrations of sucrose, pinitol, and amino acid in leaves and nodules under salt stress contributed to the osmotic adjustment in alfalfa. Cultivars differed in their response to recurrent selection: under a 160 mM NaCl-stress, aromatic amino acids and branched-chain amino acids (BCAAs) increased in nodules of B-ST3 as compared with B-TS0, while these accumulations were not observed in H-TS3. BCAAs are known to control bacteroid development and their accumulation under severe stress could have contributed to the high nodulation of B-TS3.

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