Characterisation of the whole-genome wide hexokinase gene family unravels the functional divergence in pear (Pyrus bretschneideri Rehd.)

Hexokinase genes (HXK) encode enzymes that play an important role in fruit quality and plant development because they participate in the first step of the glycolytic pathway for sugar accumulation and metabolism. In this study, the authors conducted analysis of the phylogeny, gene structure, and expression of HXK genes in pear (Pyrus bretschneideri Rehd.), comparing them with 7 other plant species. A total of 10 HXK protein sequences from pear and 33 HXKs from 7 other species were identified and clustered into 4 groups, matching their motif classification. Duplication events and motif structure variation attributed the diversification of HXK genes, supported by differential expression pattern of PbrHXKs from pear fruit transcriptome data and qRT – PCR verification. Combining pear fruit soluble sugar content data and analyses above, PbrHXK1and PbrHXK3 were identified as important candidate genes in sorbitol, fructose, and glucose accumulation during pear fruit development. PbrHXK1and PbrHXK3 were identified as important candidate genes in sorbitol, fructose, and glucose accumulation during pear fruit development. Subsequent research on these highly expressed PbrHXKs will benefit the enhancement of sugar content and quality in pear.

己糖激酶基因（Hexokinase, HXK）编码的酶类在果实品质调控与植物生长发育过程中发挥关键作用，因其参与糖积累与代谢的糖酵解通路的第一步反应。本研究以白梨（*Pyrus bretschneideri* Rehd.）为材料，对其HXK基因开展系统发育、基因结构及表达模式分析，并与其他7种植物的HXK基因进行比较。研究共鉴定得到白梨的10条HXK蛋白序列，以及另外7个物种的33条HXK蛋白序列；所有序列经聚类后分为4个类群，与基序分类结果一致。基因复制事件与基序结构变异是HXK基因家族分化的主要驱动力，该结论得到白梨果实转录组数据中PbrHXKs差异表达模式以及实时定量逆转录聚合酶链式反应（qRT-PCR）验证结果的支持。结合白梨果实可溶性糖含量数据与上述分析结果，PbrHXK1与PbrHXK3被鉴定为调控梨果实发育过程中山梨醇、果糖及葡萄糖积累的重要候选基因。PbrHXK1与PbrHXK3被确定为梨果实发育过程中山梨醇、果糖与葡萄糖积累的关键候选基因。后续针对这些高表达PbrHXK基因的研究，将有助于提升梨果实的糖含量与整体品质。