title: Exophiala sp. LHL08 reprograms Cucumis sativus to higher growth under abiotic stresses.
abstract: Endophytic fungi are potential sources of secondary metabolites; however, they are little known for phytohormones secretion and amelioration of plant growth under abiotic stresses. We isolated a novel endophyte from the roots of Cucumis sativus and identified it as a strain of Exophiala sp. by sequencing internal transcribed spacer/large subunit rDNA and phylogenetic analysis. Prior to identification, culture filtrate (CF) of Exophiala sp. has shown significant growth promotion of Waito-C [a gibberellins (GAs)-deficient mutant cultivar] and Dongjin-byeo (normal GAs biosynthesis cultivar) rice seedlings. CF analysis of Exophiala sp. showed the presence of physiologically active GAs (GA₁, GA₃, GA₄ and GA₇) and inactive GAs (GA₅, GA₈, GA₉, GA₁₂ and GA₂₀). Exophiala sp. had higher GAs in its CF than wild-type strain of Gibberella fujikuroi except GA₃. Influence of Exophiala sp. was assessed on cucumber plant's growth and endogenous abscisic acid (ABA), salicylic acid (SA) and bioactive GAs under salinity and drought stresses. Exophiala sp.-treated plants have shown significantly higher growth and rescued the host plants from stress promulgated water deficit, osmotic and cellular damage. The altered levels of stress-responsive ABA showed low level of stress confined to endophyte-applied plants than control. Elevated levels of SA and bioactive GAs (GA₃ and GA₄) in endophyte-associated plants suggest stress-modulating response toward salinity and drought. In conclusion, symbiotic relations between Exophiala and cucumber have reprogrammed the host plant growth under abiotic stresses, thus indicating a possible threshold role of endophytic fungi in stress alleviation. This study could be extended for improving agricultural productivity under extreme environmental conditions.
authors: School of Applied Biosciences, Kyungpook National University, Daegu, Republic of Korea.
authors: Abdul L
authors: AL
authors: Khan
authors: Muhammad
authors: M
authors: Hamayun
authors: Nadeem
authors: N
authors: Ahmad
authors: Muhammad
authors: M
authors: Waqas
authors: Sang-Mo
authors: SM
authors: Kang
authors: Yoon-Ha
authors: YH
authors: Kim
authors: In-Jung
authors: IJ
authors: Lee
mesh_terms: D000040:Abscisic Acid / Q000032:analysis; D018553:Cucumis sativus / Q000254:growth & development* / Q000382:microbiology; D004271:DNA, Fungal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D055864:Droughts; D060026:Endophytes / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005093:Exophiala / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D005875:Gibberellins / Q000096:biosynthesis*; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D018517:Plant Roots / Q000382:microbiology*; D020156:Salicylic Acid / Q000032:analysis; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological
chemical_list: D004271:DNA, Fungal; D004275:DNA, Ribosomal; D005875:Gibberellins; D010937:Plant Growth Regulators; D012965:Sodium Chloride; D000040:Abscisic Acid; D020156:Salicylic Acid