Sugar-mediated semidian oscillation of gene expression in the cassava storage root regulates starch synthesis

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Starch branching enzyme (SBE) activity in the cassava storage root exhibited a diurnal fluctuation, dictated by a transcriptional oscillation of the corresponding SBE genes. The peak of SBE activity coincided with the onset of sucrose accumulation in the storage, and we conclude that the oscillatory mechanism keeps the starch synthetic apparatus in the storage root sink in tune with the flux of sucrose from the photosynthetic source. When storage roots were uncoupled from the source, SBE expression could be effectively induced by exogenous sucrose. Turanose, a sucrose isomer that cannot be metabolized by plants, mimicked the effect of sucrose, demonstrating ... continued below

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Jansson, Christer; Baguma, Yona; Sun, Chuanxin; Boren, Mats; Olsson, Helena; Rosenqvist, Sara et al. January 15, 2008.

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Starch branching enzyme (SBE) activity in the cassava storage root exhibited a diurnal fluctuation, dictated by a transcriptional oscillation of the corresponding SBE genes. The peak of SBE activity coincided with the onset of sucrose accumulation in the storage, and we conclude that the oscillatory mechanism keeps the starch synthetic apparatus in the storage root sink in tune with the flux of sucrose from the photosynthetic source. When storage roots were uncoupled from the source, SBE expression could be effectively induced by exogenous sucrose. Turanose, a sucrose isomer that cannot be metabolized by plants, mimicked the effect of sucrose, demonstrating that downstream metabolism of sucrose was not necessary for signal transmission. Also glucose and glucose-1-P induced SBE expression. Interestingly, induction by sucrose, turanose and glucose but not glucose-1-P sustained an overt semidian (12-h) oscillation in SBE expression and was sensitive to the hexokinase (HXK) inhibitor glucosamine. These results suggest a pivotal regulatory role for HXK during starch synthesis. Abscisic acid (ABA) was another potent inducer of SBE expression. Induction by ABA was similar to that of glucose-1-P in that it bypassed the semidian oscillator. Both the sugar and ABA signaling cascades were disrupted by okadaic acid, a protein phosphatase inhibitor. Based on these findings, we propose a model for sugar signaling in regulation of starch synthesis in the cassava storage root.

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  • Journal Name: Plant Signaling&Behavior

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  • Report No.: LBNL-225E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 927890
  • Archival Resource Key: ark:/67531/metadc894515

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • January 15, 2008

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  • Sept. 27, 2016, 1:39 a.m.

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  • Sept. 29, 2017, 5:58 p.m.

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Jansson, Christer; Baguma, Yona; Sun, Chuanxin; Boren, Mats; Olsson, Helena; Rosenqvist, Sara et al. Sugar-mediated semidian oscillation of gene expression in the cassava storage root regulates starch synthesis, article, January 15, 2008; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc894515/: accessed October 22, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.