title: Grape hexokinases are involved in the expression regulation of sucrose synthase- and cell wall invertase-encoding genes by glucose and ABA.
abstract: Hexokinase (HXK, EC 2.7.1.1) is a multifunctional protein that both is involved in catalyzing the first step of glycolysis and plays an important role in sugar signaling. However, the supporting genetic evidence on hexokinases (CsHXKs) from grape (Vitis vinifera L. cv. Cabernet Sauvignon) berries has been lacking. Here, to investigate the role of CsHXK isoforms as glucose (Glc) and abscisic acid (ABA) sensors, we cloned two hexokinase isozymes, CsHXK1 and CsHXK2 with highly conserved genomic structure of nine exons and eight introns. We also found adenosine phosphate binding, substrate recognition and connection sites in their putative proteins. During grape berry development, the expression profiles of two CsHXK isoforms, sucrose synthases (SuSys) and cell wall invertase (CWINV) genes increased concomitantly with high levels of endogenous Glc and ABA. Furthermore, we showed that in wild type grape berry calli (WT), glucose repressed the expression levels of sucrose synthase (SuSy) and cell wall invertase (CWINV) genes, while ABA increased their expression levels. ABA could not only effectively improve the expression levels of SuSy and CWINV, but also block the repression induced by glucose on the expression of both genes. However, after silencing CsHXK1 or CsHXK2 in grape calli, SuSy and CWINV expression were enhanced, and the expressions of the two genes are insensitive in response to Glc treatment. Interestingly, exogenous ABA alone could not or less increase SuSy and CWINV expression in silencing CsHXK1 or CsHXK2 grape calli compared to WT. Meantime, ABA could not block the repression induced by glucose on the expression of SuSy and CWINV in CsHXK1 or CsHXK2 mutants. Therefore, Glc signal transduction depends on the regulation of CsHXK1 or CsHXK2. ABA signal was also disturbed by CsHXK1 or CsHXK2 silencing. The present results provide new insights into the regulatory role of Glc and ABA on the enzymes related to sugar metabolism in grape berry.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Qinghua East Road No 17, Haidian District, Beijing, 100083, China. wangxqbj@163.com.
authors.forename: Xiu-Qin
authors.initials: XQ
authors.lastname: Wang
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Qinghua East Road No 17, Haidian District, Beijing, 100083, China.
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Zheng
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Qinghua East Road No 17, Haidian District, Beijing, 100083, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Lin
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Qinghua East Road No 17, Haidian District, Beijing, 100083, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Yu
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Qinghua East Road No 17, Haidian District, Beijing, 100083, China.
authors.forename: Li-Hui
authors.initials: LH
authors.lastname: Sun
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University, Qinghua East Road No 17, Haidian District, Beijing, 100083, China.
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Li
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000595:Amino Acid Sequence; D002473:Cell Wall / Q000201:enzymology; D005638:Fruit / Q000201:enzymology / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D006593:Hexokinase / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D027843:Vitis / Q000201:enzymology*; D043324:beta-Fructofuranosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D000040:Abscisic Acid; D005964:Glucosyltransferases; C022699:sucrose synthase; D006593:Hexokinase; D043324:beta-Fructofuranosidase; D005947:Glucose
keywords: Abscisic acid; Cell wall invertase; Glucose; Grape (Vitis vinifera L.); Hexokinase; Sucrose synthase