title: Transgenic expression of the Trichoderma harzianum hsp70 gene increases Arabidopsis resistance to heat and other abiotic stresses.
abstract: The ability of some Trichoderma strains, a biological control agent, to overcome extreme environmental conditions has previously been reported and related to heat-shock proteins (HSPs). These proteins are induced environmentally and are involved in important processes, acting as molecular chaperones in all organisms. In a previous study, we demonstrated, by overexpression, that the Trichoderma harzianum hsp70 gene conferred tolerance to heat and other abiotic stresses to this fungus. In this work, we investigate the function of the T. harzianum T34 hsp70 gene in Arabidopsis thaliana. We analyze transgenic plant responses under adverse environmental conditions and the expression levels of a set of seven stress genes, using quantitative RT-PCR. As expected, transgenic plants expressing the T. harzianum hsp70 gene exhibited enhanced tolerance to heat stress. In addition, they did not show growth inhibition and, after heat pre-treatment, transgenic seedlings were more tolerant to osmotic, salt and oxidative stresses with respect to the wild-type behavior. Transgenic lines also had increased transcript levels of the Na(+)/H(+) exchanger 1 (SOS1) and ascorbate peroxidase 1 (APX1) genes, involved in salt and oxidative stress responses, respectively. However, the heat-shock factor (HSF) and four HSP genes tested were down-regulated in 35S:hsp70 plants. Overall, our results indicate that hsp70 confers tolerance to heat and other abiotic stresses and that the fungal HSP70 protein acts as a negative regulator of the HSF transcriptional activity in Arabidopsis.
authors.affiliation: Centro Hispano-Luso de Investigaciones Agrarias (CIALE), Departamento de Microbiología y Genética, Universidad de Salamanca, Río Duero 12, 37185 Villamayor, Salamanca, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Montero-Barrientos
authors.forename: Rosa
authors.initials: R
authors.lastname: Hermosa
authors.forename: Rosa E
authors.initials: RE
authors.lastname: Cardoza
authors.forename: Santiago
authors.initials: S
authors.lastname: Gutiérrez
authors.forename: Carlos
authors.initials: C
authors.lastname: Nicolás
authors.forename: Enrique
authors.initials: E
authors.lastname: Monte
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D018525:Germination; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics; D006358:Hot Temperature; D018546:Hypocotyl / Q000254:growth & development; D009997:Osmotic Pressure; D018384:Oxidative Stress / Q000235:genetics; D010641:Phenotype; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological; D014242:Trichoderma / Q000235:genetics*
chemical_list: D029681:Arabidopsis Proteins; D018840:HSP70 Heat-Shock Proteins