Inositol Phosphates and Their Metabolism in Plants

Murthy, Pushpalatha P. N.

doi:10.1007/978-1-4613-0343-5_8

Cited by 10 publications

(4 citation statements)

References 72 publications

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“…Disruption of the myo -inositol metabolic pathway may have a negative effect on seed viability due to myo -inositol’s multifunctional nature in plant metabolism. In fact, several such effects that were found in this study are in accordance with the roles of myo -inositol ( Loewus et al, 1973 ; Murthy, 1996 ; Obendorf, 1997 ; Peterbauer et al, 1998 ; Peterbauer and Richter, 1998 ; Slovin et al, 1999 ; Loewus and Murthy, 2000 ). For example, significant enrichment was found for genes functioning in the auxin pathway, cell death, cell wall metabolism, stress processes, and other carbohydrate metabolic pathways requiring myo -inositol as a precursor.…”

Section: Discussionsupporting

confidence: 91%

Network Inference of Transcriptional Regulation in Germinating Low Phytic Acid Soybean Seeds

et al. 2021

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The low phytic acid (lpa) trait in soybeans can be conferred by loss-of-function mutations in genes encoding myo-inositol phosphate synthase and two epistatically interacting genes encoding multidrug-resistance protein ATP-binding cassette (ABC) transporters. However, perturbations in phytic acid biosynthesis are associated with poor seed vigor. Since the benefits of the lpa trait, in terms of end-use quality and sustainability, far outweigh the negatives associated with poor seed performance, a fuller understanding of the molecular basis behind the negatives will assist crop breeders and engineers in producing variates with lpa and better germination rate. The gene regulatory network (GRN) for developing low and normal phytic acid soybean seeds was previously constructed, with genes modulating a variety of processes pertinent to phytic acid metabolism and seed viability being identified. In this study, a comparative time series analysis of low and normal phytic acid soybeans was carried out to investigate the transcriptional regulatory elements governing the transitional dynamics from dry seed to germinated seed. GRNs were reverse engineered from time series transcriptomic data of three distinct genotypic subsets composed of lpa soybean lines and their normal phytic acid sibling lines. Using a robust unsupervised network inference scheme, putative regulatory interactions were inferred for each subset of genotypes. These interactions were further validated by published regulatory interactions found in Arabidopsis thaliana and motif sequence analysis. Results indicate that lpa seeds have increased sensitivity to stress, which could be due to changes in phytic acid levels, disrupted inositol phosphate signaling, disrupted phosphate ion (Pi) homeostasis, and altered myo-inositol metabolism. Putative regulatory interactions were identified for the latter two processes. Changes in abscisic acid (ABA) signaling candidate transcription factors (TFs) putatively regulating genes in this process were identified as well. Analysis of the GRNs reveal altered regulation in processes that may be affecting the germination of lpa soybean seeds. Therefore, this work contributes to the ongoing effort to elucidate molecular mechanisms underlying altered seed viability, germination and field emergence of lpa crops, understanding of which is necessary in order to mitigate these problems.

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Section: Discussionsupporting

confidence: 91%

Network Inference of Transcriptional Regulation in Germinating Low Phytic Acid Soybean Seeds

et al. 2021

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“…Its importance to plant metabolism is evidenced in a recent volume dedicated to myo-inositol phosphates (Biswas et al, 1996). In addition to galactinol biosynthesis (discussed above), myo-inositol is a precursor to other cyclitols, O-methyl inositols, phytic acid and phytin, other inositol phosphates, phosphoinositides and membrane-protein anchors, glucuronic acid and pentoses (arabinose and xylose) for cell wall biosynthesis, and indole esters (Loewus et at, 1990;Murthy, 1996;Raboy and Gerbasi, 1996). Myo-inositol-1phosphate synthase (INPS 1; EC 5.5.1.4) converts a-D-glucopyranosyl-6-phosphate to lL-myo-inositol-1phosphate (a.k.a.…”

Section: Myo-inositol Biosynthesismentioning

confidence: 99%

Oligosaccharides and galactosyl cyclitols in seed desiccation tolerance

1997

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Soluble carbohydrates are one of multiple components required for the acquisition of desiccation tolerance during seed development and maturation. Sucrose and the raffinose series of oligosaccharides have been extensively studied in relation to seed desiccation tolerance. These galactosyl sucrose oligosaccharides are present in viable tissues of many edible seeds, especially the legumes, and contribute to flatulence after ingestion. A reduction in oligosaccharides of the raffinose series is desired by nutritionists but, if present at less than a threshold level, this this may result in reduced desiccation tolerance and storability of seeds. Some seeds that have very low amounts of raffinose and stachyose accumulate galactosyl cyclitols and small amounts of free cyclitols. Galactosyl cyclitols present in various seeds include galactosyl or methyl derivatives of myo-inositol, D-pinitol, D-chiro-inositol, D-ononitol, and scyllo-inositol. Castor bean seeds accumulate galactinol and buck-wheat seeds accumulate fagopyritol in addition to sucrose. Fagopyritol accumulation is associated with the acquisition of desiccation tolerance in buckwheat seeds. The galactosyl sucrose and galactosyl cyclitol soluble carbohydrates in maturing seeds have been proposed to have various roles in desiccation tolerance including non-toxic and non-reducing forms of seed storage products and intracellular osmotic agents contributing to the structural stability of organelles, membranes, enzymes and proteins, other macromolecules, and the glassy state. Ether derivatives of cyclitols may form liquid crystals. Methyl ether derivatives of cyclitols may have roles as cryoprotectants, desiccation protectants, and hydroxyl radical scavengers.

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“…The hatched box shows a representative area for data collection, which is averaged and represented in graphs hydrolyzed by plant extracts to inositol bisphosphates, Ins(1,4)P 2 and Ins(4,5)P 2 , inositol monophosphates Ins(1)P 1 and Ins(4)P 1 and ®nally to inositol (Murthy 1996). The ratios of intermediate inositol monophosphates and bisphosphates varied with the tissues being studied, as did pH optima and sensitivity to ions such as Mg 2+ , Li + , and Ca 2+ (Murthy 1996). Since these studies were conducted in cell lysates, the preferred pathways of Ins(1,4,5)P 3 catabolism in the cytosol of the living cell have remained unclear.…”

Section: Discussionmentioning

confidence: 99%

Inositol 1,4,5 trisphosphate is inactivated by a 5-phosphatase in stamen hair cells of Tradescantia

DePass

Crain

Hepler

2001

Planta

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Inositol 1,4,5 trisphosphate [Ins(1,4,5)P3] is produced from the hydrolysis of phosphatidylinositol 4,5 bisphosphate, and as part of a second-messenger signal transduction mechanism, induces release of Ca2+ from internal stores in both plant and animal systems. It is less well established how the active Ins(1,4,5)P3 is inactivated. Studies in animal cells have demonstrated two separate metabolic pathways. Ins(1,4,5)P3 can be hydrolyzed by a 5-phosphatase or phosphorylated by a 3-kinase, resulting in the formation of Ins(1,4)P2 and Ins(1,3,4,5)P4, respectively, neither of which is able to mobilize intracellular Ca2+. Plant cell extracts have been reported to have hydrolytic and kinase activities that produce Ins(1,4)P2, and Ins(4,5)P2 and Ins(1,4,5,6)P4 from Ins(1,4,5)P3. These results offer little insight into the enzyme activities in the intact plant cell since the observed activities might be confined to intracellular compartments that have little if any impact on the signaling events within the cytosol that require Ins(1,4,5)P3. To resolve the mechanism of Ins(1,4,5)P3 inactivation, we microinjected stamen hair cells of Tradescantia virginiana L. with nonhydrolysable analogs of Ins(1,4,5)P3 that have been previously shown to cause Ca2+ release from intracellular stores. Our results indicate a sustained cytosolic [Ca2+] increase when cells were injected with the 5-phosphatase-insensitive 5-monophosphorothioate derivative of Ins(1,4,5)P3, in contrast to a brief transient when injected with the 3-kinase-insensitive 3-fluoro-3-deoxy Ins(1,4,5)P3 analog. We conclude that the 5-phosphatase pathway is the preferred pathway for Ins(1,4,5)P3 inactivation in the stamen hair cells of Tradescantia.

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Inositol Phosphates and Their Metabolism in Plants

Cited by 10 publications

References 72 publications

Network Inference of Transcriptional Regulation in Germinating Low Phytic Acid Soybean Seeds

Network Inference of Transcriptional Regulation in Germinating Low Phytic Acid Soybean Seeds

Oligosaccharides and galactosyl cyclitols in seed desiccation tolerance

Inositol 1,4,5 trisphosphate is inactivated by a 5-phosphatase in stamen hair cells of Tradescantia

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