Geng Meng-Ting, Yao Yuan, Wang Yun-Lin, Wu Xiao-Hui, Sun Chong, Li Rui-Mei, Fu Shao-Ping, Duan Rui-Jun, Liu Jiao, Hu Xin-Wen, Guo Jian-Chun
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.
Int J Mol Sci. 2017 May 12;18(5):1041. doi: 10.3390/ijms18051041.
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 genes () 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 genes in cassava organs or tissues demonstrated that is the dominant HXK in all the examined tissues (leaves, stems, fruits, tuber phloems, and tuber xylems). Notably, the expression of 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 (, , ). 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.
己糖激酶（HXK）蛋白在催化己糖磷酸化以及糖感知和信号传导中发挥着重要作用。为了研究HXK在木薯块根发育中的作用，我们分离并分析了七个基因（）。系统发育分析表明，木薯己糖激酶（MeHXK）家族可分为植物己糖激酶的五个亚家族。根据其N端序列，MeHXK可明显分为A 型（MeHXK1）和B型（MeHXK2 - 7）。MeHXK1 - 5均具有典型的保守区域，并且蛋白质结构与其他植物的己糖激酶相似；而MeHXK6 - 7缺少一些保守区域。对木薯器官或组织中这些基因的表达分析表明，[具体基因名称未给出]是所有检测组织（叶片、茎、果实、块根韧皮部和块根木质部）中的主要己糖激酶。值得注意的是，[具体基因名称未给出]的表达以及己糖激酶的酶活性在块根初始和膨大阶段较高，而在成熟块根阶段较低。此外，通过对己糖激酶缺陷型酵母菌株YSH7.4 - 3C（[相关具体信息未给出]）进行功能互补，鉴定了MeHXK2的己糖激酶活性。MeHXK2的基因表达和酶活性表明，它可能是木薯块根发育过程中己糖磷酸化的主要酶，参与蔗糖代谢以调节淀粉的积累。
