title: Induction of drought tolerance in cucumber plants by a consortium of three plant growth-promoting rhizobacterium strains.
abstract: Our previous work showed that a consortium of three plant growth-promoting rhizobacterium (PGPR) strains (Bacillus cereus AR156, Bacillus subtilis SM21, and Serratia sp. XY21), termed as BBS for short, was a promising biocontrol agent. The present study investigated its effect on drought tolerance in cucumber plants. After withholding watering for 13 days, BBS-treated cucumber plants had much darker green leaves and substantially lighter wilt symptoms than control plants. Compared to the control, the BBS treatment decreased the leaf monodehydroascorbate (MDA) content and relative electrical conductivity by 40% and 15%, respectively; increased the leaf proline content and the root recovery intension by 3.45-fold and 50%, respectively; and also maintained the leaf chlorophyll content in cucumber plants under drought stress. Besides, in relation to the control, the BBS treatment significantly enhanced the superoxide dismutase (SOD) activity and mitigated the drought-triggered down-regulation of the expression of the genes cAPX, rbcL, and rbcS encoding cytosolic ascorbate peroxidase, and ribulose-1,5-bisphosphate carboxy/oxygenase (Rubisco) large and small subunits, respectively, in cucumber leaves. However, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity was undetected in none of the culture solutions of three BBS constituent strains. These results indicated that BBS conferred induced systemic tolerance to drought stress in cucumber plants, by protecting plant cells, maintaining photosynthetic efficiency and root vigor and increasing some of antioxidase activities, without involving the action of ACC deaminase to lower plant ethylene levels.
authors.affiliation: Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, and Key Laboratory of Integrated Management of Crop Diseases and Pests, Nanjing Agricultural University, Ministry of Education, Nanjing, China.
authors.forename: Chun-Juan
authors.initials: CJ
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.forename: Chun
authors.initials: C
authors.lastname: Gu
authors.forename: Dong-Dong
authors.initials: DD
authors.lastname: Niu
authors.forename: Hong-Xia
authors.initials: HX
authors.lastname: Liu
authors.forename: Yun-Peng
authors.initials: YP
authors.lastname: Wang
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Guo
mesh_terms: D000222:Adaptation, Physiological; D060387:Ascorbate Peroxidases / Q000378:metabolism; D001409:Bacillus cereus / Q000502:physiology*; D001412:Bacillus subtilis / Q000502:physiology*; D019755:Carbon-Carbon Lyases / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D018553:Cucumis sativus / Q000201:enzymology / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology*; D055864:Droughts; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D008954:Models, Biological; D018515:Plant Leaves / Q000378:metabolism; D012705:Serratia / Q000502:physiology*; D013312:Stress, Physiological / Q000235:genetics; D013482:Superoxide Dismutase / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D002734:Chlorophyll; D060387:Ascorbate Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase; C033634:1-aminocyclopropane-1-carboxylate deaminase; D019755:Carbon-Carbon Lyases