title: Role of glucose-6-phosphate dehydrogenase in freezing-induced freezing resistance of Populus suaveolens.
abstract: To explore the role of glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) in the enhancement of freezing resistance induced by freezing acclimation, G6PDH was purified from the leaves of 8-week-old Populus suaveolens cuttings. The G6PDH activity in the absence or the presence of reduced dithiothreitol (DTT(red)) were determined, and the changes in superoxide dismutase (SOD), peroxides (POD) and cytosolic G6PDH activities, malondial-dehyde (MDA) content as well as freezing resistance (expressed as LT(50)) of P. suaveolens cuttings during freezing acclimation at -20 degrees C were investigated. The results showed that the purified G6PDH was probably located in the cytosol of P. suaveolens. Freezing acclimation increased the activities of SOD, POD and cytosolic G6PDH, and decreased the MDA content and LT(50) of cuttings, while 2 d of de-acclimation at 25 degrees C resulted in a decrease in SOD, POD and cytosolic G6PDH activities, and caused an increase in MDA content and LT(50). The change in cytosolic G6PDH activity was found to be closely correlated to the levels of SOD, POD and MDA, and to the degree of freezing resistance of cuttings during freezing acclimation. It is suggested that the enhancement of freezing resistance of cuttings induced by freezing acclimation is related to the distinct increase in cytosolic G6PDH activity, which may be involved in the activation of SOD and POD, and the induction of freezing resistance of cuttings.
authors.affiliation: Key Laboratory for Genetics and Breeding in Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing 100083, China. linsz2002@163.com
authors.forename: Shan-Zhi
authors.initials: SZ
authors.lastname: Lin
authors.forename: Zhi-Yi
authors.initials: ZY
authors.lastname: Zhang
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liu
authors.forename: Yuan-Zhen
authors.initials: YZ
authors.lastname: Lin
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhang
authors.forename: Bao-Qing
authors.initials: BQ
authors.lastname: Zhu
mesh_terms: D000064:Acclimatization / Q000502:physiology; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D005615:Freezing; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism*; D008315:Malondialdehyde / Q000378:metabolism; D010545:Peroxides / Q000378:metabolism; D032107:Populus / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology*; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D010545:Peroxides; D008315:Malondialdehyde; D005954:Glucosephosphate Dehydrogenase; D013482:Superoxide Dismutase