title: Expression of xyloglucan endotransglucosylase/hydrolase (XTH) genes and XET activity in ethylene treated apple and tomato fruits.
abstract: Xyloglucan endotransglucosylase/hydrolase (XTHs: EC 2.4.1.207 and/or EC 3.2.1.151), a xyloglucan modifying enzyme, has been proposed to have a role during tomato and apple fruit ripening by loosening the cell wall. Since the ripening of climacteric fruits is controlled by endogenous ethylene biosynthesis, we wanted to study whether XET activity was ethylene-regulated, and if so, which specific genes encoding ripening-regulated XTH genes were indeed ethylene-regulated. XET specific activity in tomato and apple fruits was significantly increased by the ethylene treatment, as compared with the control fruits, suggesting an increase in the XTH gene expression induced by ethylene. The 25 SlXTH protein sequences of tomato and the 11 sequences MdXTH of apple were phylogenetically analyzed and grouped into three major clades. The SlXTHs genes with highest expression during ripening were SlXTH5 and SlXTH8 from Group III-B, and in apple MdXTH2, from Group II, and MdXTH10, and MdXTH11 from Group III-B. Ethylene was involved in the regulation of the expression of different SlXTH and MdXTH genes during ripening. In tomato fruit fifteen different SlXTH genes showed an increase in expression after ethylene treatment, and the SlXTHs that were ripening associated were also ethylene dependent, and belong to Group III-B (SlXTH5 and SlXTH8). In apple fruit, three MdXTH showed an increase in expression after the ethylene treatment and the only MdXTH that was ripening associated and ethylene dependent was MdXTH10 from Group III-B. The results indicate that XTH may play an important role in fruit ripening and a possible relationship between XTHs from Group III-B and fruit ripening, and ethylene regulation is suggested.
authors.affiliation: Dpto. Biología Vegetal, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100 Burjassot, Valencia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Muñoz-Bertomeu
authors.forename: E
authors.initials: E
authors.lastname: Miedes
authors.forename: E P
authors.initials: EP
authors.lastname: Lorences
mesh_terms: D005030:Ethylenes / Q000378:metabolism*; D005638:Fruit / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D016695:Glycosyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018551:Solanum lycopersicum / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D027845:Malus / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D005030:Ethylenes; D010937:Plant Growth Regulators; C036216:ethylene; D016695:Glycosyltransferases; C473049:xyloglucan - xyloglucosyltransferase
keywords: Cell wall; Fruit ripening; Malus domestica; Solanum lycopersicum; Transglucosylation and xyloglucan; XEH; XET; XTH; xyloglucan endohydrolase; xyloglucan endotransglucosylase; xyloglucan endotransglucosylase/hydrolase