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Int. J. Mol. Sci. 2017, 18(5), 1041;

Structure, Expression, and Functional Analysis of the Hexokinase Gene Family in Cassava

College of Agriculture, Hainan University, Haikou 570228, China
Key Laboratory of Biology and Genetic Resources of Tropical Crops, Ministry of Agriculture, Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China
Prisys Biotechnologies Company Limited, Shanghai 201203, China
College of Life Science and Biotechnology, Heilongjiang Bayi Agricultural University, Daqing 163319, China
These authors contributed equally to this work.
Authors to whom correspondence should be addressed.
Academic Editor: Setsuko Komatsu
Received: 9 April 2017 / Revised: 8 May 2017 / Accepted: 8 May 2017 / Published: 12 May 2017
(This article belongs to the Section Molecular Plant Sciences)
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Hexokinase (HXK) proteins play important roles in catalyzing hexose phosphorylation and sugar sensing and signaling. To investigate the roles of HXKs in cassava tuber root development, seven HXK genes (MeHXK1–7) were isolated and analyzed. A phylogenetic analysis revealed that the MeHXK family can be divided into five subfamilies of plant HXKs. MeHXKs were clearly divided into type A (MeHXK1) and type B (MeHXK2–7) based on their N-terminal sequences. MeHXK1–5 all had typical conserved regions and similar protein structures to the HXKs of other plants; while MeHXK6–7 lacked some of the conserved regions. An expression analysis of the MeHXK genes in cassava organs or tissues demonstrated that MeHXK2 is the dominant HXK in all the examined tissues (leaves, stems, fruits, tuber phloems, and tuber xylems). Notably, the expression of MeHXK2 and the enzymatic activity of HXK were higher at the initial and expanding tuber stages, and lower at the mature tuber stage. Furthermore, the HXK activity of MeHXK2 was identified by functional complementation of the HXK-deficient yeast strain YSH7.4-3C (hxk1, hxk2, glk1). The gene expression and enzymatic activity of MeHXK2 suggest that it might be the main enzyme for hexose phosphorylation during cassava tuber root development, which is involved in sucrose metabolism to regulate the accumulation of starch. View Full-Text
Keywords: cassava; hexokinase; gene expression; yeast complementation; enzyme activities cassava; hexokinase; gene expression; yeast complementation; enzyme activities

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Geng, M.-T.; Yao, Y.; Wang, Y.-L.; Wu, X.-H.; Sun, C.; Li, R.-M.; Fu, S.-P.; Duan, R.-J.; Liu, J.; Hu, X.-W.; Guo, J.-C. Structure, Expression, and Functional Analysis of the Hexokinase Gene Family in Cassava. Int. J. Mol. Sci. 2017, 18, 1041.

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