title: Gene expression analyses in tomato near isogenic lines provide evidence for ethylene and abscisic acid biosynthesis fine-tuning during arbuscular mycorrhiza development.
abstract: Plant responses to the environment and microorganisms, including arbuscular mycorrhizal fungi, involve complex hormonal interactions. It is known that abscisic acid (ABA) and ethylene may be involved in the regulation of arbuscular mycorrhiza (AM) and that part of the detrimental effects of ABA deficiency in plants is due to ethylene overproduction. In this study, we aimed to determine whether the low susceptibility to mycorrhizal colonization in ABA-deficient mutants is due to high levels of ethylene and whether AM development is associated with changes in the steady-state levels of transcripts of genes involved in the biosynthesis of ethylene and ABA. For that, tomato (Solanum lycopersicum) ethylene overproducer epinastic (epi) mutant and the ABA-deficient notabilis (not) and sitiens (sit) mutants, in the same Micro-Tom (MT) genetic background, were inoculated with Rhizophagus clarus, and treated with the ethylene biosynthesis inhibitor aminoethoxyvinylglycine (AVG). The development of AM, as well as the steady-state levels of transcripts involved in ethylene (LeACS2, LeACO1 and LeACO4) and ABA (LeNCED) biosynthesis, was determined. The intraradical colonization in epi, not and sit mutants was significantly reduced compared to MT. The epi mutant completely restored the mycorrhizal colonization to the levels of MT with the application of 10 µM of AVG, probably due to the inhibition of the ACC synthase gene expression. The steady-state levels of LeACS2 and LeACO4 transcripts were induced in mycorrhizal roots of MT, whereas the steady-state levels of LeACO1 and LeACO4 transcripts were significantly induced in sit, and the steady-state levels of LeNCED transcripts were significantly induced in all genotypes and in mycorrhizal roots of epi mutants treated with AVG. The reduced mycorrhizal colonization in sit mutants seems not to be limited by ethylene production via ACC oxidase regulation. Both ethylene overproduction and ABA deficiency impaired AM fungal colonization in tomato roots, indicating that, besides hormonal interactions, a fine-tuning of each hormone level is required for AM development.
authors.affiliation: Departamento de Agronomia, Universidade Federal Rural de Pernambuco, Rua Dom Manoel de Medeiros, s/n, Dois Irmãos, Recife, Pernambuco, 52171-900, Brazil.|Departamento de Ciência do Solo, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, Piracicaba, São Paulo, 13418-900, Brazil.
authors.forename: Giselle Gomes Monteiro
authors.initials: GGM
authors.lastname: Fracetto
authors.affiliation: Laboratório de Controle Hormonal do Desenvolvimento Vegetal, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, Piracicaba, São Paulo, 13418-900, Brazil.
authors.forename: Lázaro Eustáquio Pereira
authors.initials: LEP
authors.lastname: Peres
authors.affiliation: Departamento de Ciência do Solo, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Av. Pádua Dias, 11, Piracicaba, São Paulo, 13418-900, Brazil. mlambais@usp.br.
authors.forename: Marcio Rodrigues
authors.identifier: http://orcid.org/0000-0002-7218-3665
authors.initials: MR
authors.lastname: Lambais
mesh_terms: D000040:Abscisic Acid / Q000096:biosynthesis / Q000378:metabolism*; D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D005030:Ethylenes / Q000096:biosynthesis / Q000378:metabolism*; D005658:Fungi / Q000254:growth & development*; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D008190:Lyases / Q000037:antagonists & inhibitors; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D038821:Mycorrhizae / Q000254:growth & development* / Q000378:metabolism; D018517:Plant Roots / Q000382:microbiology
chemical_list: D005030:Ethylenes; D000040:Abscisic Acid; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase; C088137:aminoethoxyvinylglycine; D005998:Glycine
keywords: 9-Cis-epoxycarotenoid dioxygenase; ACC oxidase; ACC synthase; Arbuscular mycorrhiza; Micro-Tom