A Fungal Endoglucanase with Plant Cell Wall Extension Activity

Yuan, Sheng; Wu, Yajun; Cosgrove, Daniel J.

doi:10.1104/pp.127.1.324

Cited by 109 publications

(110 citation statements)

References 42 publications

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“…One enzyme was XEG, the XyG-specific endoglucanase, or "xyloglucanase," from Aspergillus aculeatus used by Pauly et al (1999) to define the enzyme-accessible tethers, loops, and free strands of XyG between cellulose microfibrils. The second enzyme, Cel12A from Hypocrea jecorina, digests both XyG and cellulose (Yuan et al, 2001;Karlsson et al, 2002). The third enzyme, CEG from Aspergillus niger, is a cellulose-specific endoglucanase, or "cellulase," according to the supplier (www.megazyme.org).…”

Section: Distinctive Actions Of Family-12 Endoglucanasesmentioning

confidence: 99%

A Revised Architecture of Primary Cell Walls Based on Biomechanical Changes Induced by Substrate-Specific Endoglucanases

2012

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Xyloglucan is widely believed to function as a tether between cellulose microfibrils in the primary cell wall, limiting cell enlargement by restricting the ability of microfibrils to separate laterally. To test the biomechanical predictions of this “tethered network” model, we assessed the ability of cucumber (Cucumis sativus) hypocotyl walls to undergo creep (long-term, irreversible extension) in response to three family-12 endo-β-1,4-glucanases that can specifically hydrolyze xyloglucan, cellulose, or both. Xyloglucan-specific endoglucanase (XEG from Aspergillus aculeatus) failed to induce cell wall creep, whereas an endoglucanase that hydrolyzes both xyloglucan and cellulose (Cel12A from Hypocrea jecorina) induced a high creep rate. A cellulose-specific endoglucanase (CEG from Aspergillus niger) did not cause cell wall creep, either by itself or in combination with XEG. Tests with additional enzymes, including a family-5 endoglucanase, confirmed the conclusion that to cause creep, endoglucanases must cut both xyloglucan and cellulose. Similar results were obtained with measurements of elastic and plastic compliance. Both XEG and Cel12A hydrolyzed xyloglucan in intact walls, but Cel12A could hydrolyze a minor xyloglucan compartment recalcitrant to XEG digestion. Xyloglucan involvement in these enzyme responses was confirmed by experiments with Arabidopsis (Arabidopsis thaliana) hypocotyls, where Cel12A induced creep in wild-type but not in xyloglucan-deficient (xxt1/xxt2) walls. Our results are incompatible with the common depiction of xyloglucan as a load-bearing tether spanning the 20- to 40-nm spacing between cellulose microfibrils, but they do implicate a minor xyloglucan component in wall mechanics. The structurally important xyloglucan may be located in limited regions of tight contact between microfibrils.

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Section: Distinctive Actions Of Family-12 Endoglucanasesmentioning

confidence: 99%

A Revised Architecture of Primary Cell Walls Based on Biomechanical Changes Induced by Substrate-Specific Endoglucanases

2012

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“…It is expected that they could be associated to a genetic variability of the rheological char-acteristics of cell walls, depending, for instance, on genes that code for expansins (Cosgrove, 2000), endoglucanases (Yuan et al, 2001), or xyloglucan endotransglycosylase (Reidy et al, 2001).…”

Section: Interpretation Of Qtls Of Responses To Environmental Conditionsmentioning

confidence: 99%

Combining Quantitative Trait Loci Analysis and an Ecophysiological Model to Analyze the Genetic Variability of the Responses of Maize Leaf Growth to Temperature and Water Deficit

et al. 2003

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Ecophysiological models predict quantitative traits of one genotype in any environment, whereas quantitative trait locus (QTL) models predict the contribution of alleles to quantitative traits under a limited number of environments. We have combined both approaches by dissecting into effects of QTLs the parameters of a model of maize (Zea mays) leaf elongation rate (LER; H. Ben Haj Salah, F. Tardieu [1997] Plant Physiol 114: 893-900). Response curves of LER to meristem temperature, water vapor pressure difference, and soil water status were established in 100 recombinant inbred lines (RILs) of maize in six experiments carried out in the field or in the greenhouse. All responses were linear and common to different experiments, consistent with the model. A QTL analysis was carried out on the slopes of these responses by composite interval mapping confirmed by bootstrap analysis. Most QTLs were specific of one response only. QTLs of abscisic acid concentration in the xylem sap colocalized with QTLs of response to soil water deficit and conferred a low response. Each parameter of the ecophysiological model was computed as the sum of QTL effects, allowing calculation of parameters for 11 new RILs and two parental lines. LERs were simulated and compared with measurements in a growth chamber experiment. The combined model accounted for 74% of the variability of LER, suggesting that it has a general value for any RIL under any environment.In an agricultural context, a plant that tolerates water deficit can produce a maximum harvested biomass under moderate water deficits. Involved mechanisms are not necessarily common with those underlying the ability of cells to survive tissue dehydration (e.g. Cushman and Bohnert, 2000; Seki et al., 2001). In maize (Zea mays), moderate water deficits usually cause no appreciable decrease in leaf water status because of an efficient stomatal control combining hydraulic and chemical messages (Tardieu and Davies, 1993;Wilkinson et al., 1998). A similar combination of messages allows maize plants to dramatically reduce leaf elongation rate (LER) under moderate water deficits sensed either in the soil or in the air, before that leaf water status is appreciably altered (Sharp et al., 2000;Tardieu et al., 2000). Reductions in stomatal conductance and in leaf expansion decrease transpiration rate, thereby saving soil water and maintaining leaf water potential at high values. They also reduce photosynthesis, growth, and yield, so optimum tolerance strategies cannot be common to different climatic scenarios. Plants with steepest responses might be most adapted to scenarios with most severe water deficits, whereas maintenance of growth and photosynthesis under deficit might be appropriate for scenarios with milder deficits. Therefore, identification of sources of variability in the responses to water deficit is necessary for designing plants adapted to a given climatic scenario.We aimed to identify and analyze the genetic variability of responses of leaf elongation to water deficits caused eit...

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“…Yet another variant on the optically thin RIAF model is the luminous hot accretion flow (LHAF) model of Yuan (2001). As we discussed above, unless alpha is large, RIAF's have a maximum accretion rate above which the solutions with advective cool-ing do not exist.…”

Section: Other Variantsmentioning

confidence: 99%

General Overview of Black Hole Accretion Theory

Blaes

2013

Space Sci Rev

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I provide a broad overview of the basic theoretical paradigms of black hole accretion flows. Models that make contact with observations continue to be mostly based on the four decade old alpha stress prescription of Shakura & Sunyaev (1973), and I discuss the properties of both radiatively efficient and inefficient models, including their local properties, their expected stability to secular perturbations, and how they might be tied together in global flow geometries. The alpha stress is a prescription for turbulence, for which the only existing plausible candidate is that which develops from the magnetorotational instability (MRI). I therefore also review what is currently known about the local properties of such turbulence, and the physical issues that have been elucidated and that remain uncertain that are relevant for the various alpha-based black hole accretion flow models.

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A Fungal Endoglucanase with Plant Cell Wall Extension Activity

Cited by 109 publications

References 42 publications

A Revised Architecture of Primary Cell Walls Based on Biomechanical Changes Induced by Substrate-Specific Endoglucanases

A Revised Architecture of Primary Cell Walls Based on Biomechanical Changes Induced by Substrate-Specific Endoglucanases

Combining Quantitative Trait Loci Analysis and an Ecophysiological Model to Analyze the Genetic Variability of the Responses of Maize Leaf Growth to Temperature and Water Deficit

General Overview of Black Hole Accretion Theory

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