title: Physiological and biochemical characterisation of watered and drought-stressed barley mutants in the HvDWARF gene encoding C6-oxidase involved in brassinosteroid biosynthesis.
abstract: Brassinosteroids (BR) are plant steroid hormones that were discovered more than thirty years ago, but their physiological function has yet to be fully explained. The aim of the study was to answer the question of whether/how disturbances in the production of BR in barley affects the plant's metabolism and development under conditions of optimal watering and drought. Mutants with an impaired production of BR are one of the best tools in research aimed at understanding the mechanisms of action of these hormones. The study used barley cultivars with a normal BR synthesis (wild type) and semi-dwarf allelic mutants with an impaired activity of C6-oxidase (mutation in HvDWARF), which resulted in a decreased BR synthesis. Half of the plants were subjected to drought stress in the seedling stage and the other half were watered optimally. Plants with impaired BR production were characterised by a lower height and developmental retardation. Under both optimal watering and drought, BR synthesis disorders caused the reduced production of ABA and cytokinins, but not auxins. The BR mutants also produced less osmoprotectant (proline). The optimally watered and drought-stressed mutants accumulated less sucrose, which was accompanied by changes in the production of other soluble sugars. The increased content of fructooligosaccharide (kestose) in optimally watered mutants would suggest that BR is a negative regulator of kestose production. The decreased level of nystose in the drought-stressed mutants also suggests BR involvement in the regulation of the production of this fructooligosaccharide. The accumulation of the transcripts of genes associated with stress response (hsp90) was lower in the watered and drought-stressed BR-deficient mutants. In turn, the lower efficiency of photosystem II and the net photosynthetic rate in mutants was revealed only under drought conditions. The presented research allows for the physiological and biochemical traits of two BR-barley mutants to be characterised, which helps BR function to be understood. The knowledge can also be a good starting point for some breeding companies that are interested in introducing new semi-dwarf barley cultivars.
authors.affiliation: The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239 Krakow, Poland. Electronic address: ania@belanna.strefa.pl.
authors.forename: Anna
authors.initials: A
authors.lastname: Janeczko
authors.affiliation: Department of Genetics, Faculty of Biology and Environment Protection, University of Silesia, Jagiellonska 28, 40-032 Katowice, Poland.
authors.forename: Damian
authors.initials: D
authors.lastname: Gruszka
authors.affiliation: Department of Plant Physiology, University of Agriculture in Krakow, Podłużna 3, 30-239 Krakow, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Pociecha
authors.affiliation: The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239 Krakow, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Dziurka
authors.affiliation: Institute of Biology, Pedagogical University, Podchorążych 2, 30-084 Krakow, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Filek
authors.affiliation: Department of Plant Physiology, University of Agriculture in Krakow, Podłużna 3, 30-239 Krakow, Poland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Jurczyk
authors.affiliation: Department of Plant Physiology, Faculty of Agriculture and Biology, Warsaw Agricultural University WULS-SGGW, Nowoursynowska 159, 02-776 Warsaw, Poland.
authors.forename: Hazem M
authors.initials: HM
authors.lastname: Kalaji
authors.affiliation: Institute of Biology, The Jan Kochanowski University, Świętokrzyska 15, 25-406 Kielce, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Kocurek
authors.affiliation: The Franciszek Górski Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239 Krakow, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Waligórski
mesh_terms: D060406:Brassinosteroids / Q000096:biosynthesis*; D003583:Cytokinins / Q000378:metabolism; D055864:Droughts; D001467:Hordeum / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D010788:Photosynthesis; D014867:Water / Q000378:metabolism*
chemical_list: D060406:Brassinosteroids; D003583:Cytokinins; D014867:Water
keywords: ABA; Barley mutants; Brassinosteroids; Carbohydrates; Cytokinins; Drought; Photosynthesis