Structure, expression, and functional analysis of the hexokinase gene family in rice (Oryza sativa L.) |
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Authors: | Jung-Il Cho Nayeon Ryoo Seho Ko Sang-Kyu Lee Junok Lee Ki-Hong Jung Youn-Hyung Lee Seong Hee Bhoo Joris Winderickx Gynheung An Tae-Ryong Hahn Jong-Seong Jeon |
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Affiliation: | (1) Plant Metabolism Research Center & Graduate School of Biotechnology, Kyung Hee University, 449-701 Yongin, Republic of South Korea;(2) Division of Molecular and Life Sciences, Pohang University of Science and Technology, 790-784 Pohang, Republic of South Korea;(3) Functional Biology, Katholieke Universiteit Leuven, Plantkunde en Microbiologie, Kasteelpark Arenberg 31, 3001 Heverlee, Belgium |
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Abstract: | Hexokinase (HXK) is a dual-function enzyme that both phosphorylates hexose to form hexose 6−phosphate and plays an important role in sugar sensing and signaling. To investigate the roles of hexokinases in rice growth and development, we analyzed rice sequence databases and isolated ten rice hexokinase cDNAs, OsHXK1 (Oryza sativa Hexokinase 1) through OsHXK10. With the exception of the single-exon gene OsHXK1, the OsHXKs all have a highly conserved genomic structure consisting of nine exons and eight introns. Gene expression profiling revealed that OsHXK2 through OsHXK9 are expressed ubiquitously in various organs, whereas OsHXK10 expression is pollen-specific. Sugars induced the expression of three OsHXKs, OsHXK2, OsHXK5, and OsHXK6, in excised leaves, while suppressing OsHXK7 expression in excised leaves and immature seeds. The hexokinase activity of the OsHXKs was confirmed by functional complementation of the hexokinase-deficient yeast strain YSH7.4-3C (hxk1, hxk2, glk1). OsHXK4 was able to complement this mutant only after the chloroplast-transit peptide was removed. The subcellular localization of OsHXK4 and OsHXK7, observed with green fluorescent protein (GFP) fusion constructs, indicated that OsHXK4 is a plastid-stroma-targeted hexokinase while OsHXK7 localizes to the cytosol.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. |
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Keywords: | Gene expression Gene structure Hexokinase Oryza Subcellular localization Yeast complementation |
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