title: Ethylene suppresses tomato (Solanum lycopersicum) fruit set through modification of gibberellin metabolism.
abstract: Fruit set in angiosperms marks the transition from flowering to fruit production and a commitment to seed dispersal. Studies with Solanum lycopersicum (tomato) fruit have shown that pollination and subsequent fertilization induce the biosynthesis of several hormones, including auxin and gibberellins (GAs), which stimulate fruit set. Circumstantial evidence suggests that the gaseous hormone ethylene may also influence fruit set, but this has yet to be substantiated with molecular or mechanistic data. Here, we examined fruit set at the biochemical and genetic levels, using hormone and inhibitor treatments, and mutants that affect auxin or ethylene signaling. The expression of system-1 ethylene biosynthetic genes and the production of ethylene decreased during pollination-dependent fruit set in wild-type tomato and during pollination-independent fruit set in the auxin hypersensitive mutant iaa9-3. Blocking ethylene perception in emasculated flowers, using either the ethylene-insensitive Sletr1-1 mutation or 1-methylcyclopropene (1-MCP), resulted in elongated parthenocarpic fruit and increased cell expansion, whereas simultaneous treatment with the GA biosynthesis inhibitor paclobutrazol (PAC) inhibited parthenocarpy. Additionally, the application of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) to pollinated ovaries reduced fruit set. Furthermore, Sletr1-1 parthenocarpic fruits did not exhibit increased auxin accumulation, but rather had elevated levels of bioactive GAs, most likely reflecting an increase in transcripts encoding the GA-biosynthetic enzyme SlGA20ox3, as well as a reduction in the levels of transcripts encoding the GA-inactivating enzymes SlGA2ox4 and SlGA2ox5. Taken together, our results suggest that ethylene plays a role in tomato fruit set by suppressing GA metabolism.
authors.affiliation: Graduate School of Environmental Sciences, Gene Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Shinozaki
authors.affiliation: Graduate School of Environmental Sciences, Gene Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Hao
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22, Suehiro, Tsurumi, Yokohama, 230-0045, Japan.
authors.forename: Mikiko
authors.initials: M
authors.lastname: Kojima
authors.affiliation: RIKEN Center for Sustainable Resource Science, 1-7-22, Suehiro, Tsurumi, Yokohama, 230-0045, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sakakibara
authors.affiliation: Graduate School of Environmental Sciences, Gene Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ozeki-Iida
authors.affiliation: Boyce Thompson Institute for Plant Research, Ithaca, NY, 14853, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Boyce Thompson Institute for Plant Research, Ithaca, NY, 14853, USA.
authors.forename: Zhangjun
authors.initials: Z
authors.lastname: Fei
authors.affiliation: Partner State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Silin
authors.initials: S
authors.lastname: Zhong
authors.affiliation: Boyce Thompson Institute for Plant Research, Ithaca, NY, 14853, USA.|U.S. Department of Agriculture/Agriculture Research Service, Robert W. Holley Centre for Agriculture and Health, Ithaca, NY, 14853, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Giovannoni
authors.affiliation: Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Jocelyn K C
authors.initials: JK
authors.lastname: Rose
authors.affiliation: Graduate School of Environmental Sciences, Gene Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Okabe
authors.affiliation: Graduate School of Environmental Sciences, Gene Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Heta
authors.affiliation: Graduate School of Environmental Sciences, Gene Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ezura
authors.affiliation: Graduate School of Environmental Sciences, Gene Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8572, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Ariizumi
mesh_terms: D005030:Ethylenes / Q000378:metabolism*; D035264:Flowers / Q000378:metabolism; D017343:Genes, Plant; D005875:Gibberellins / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism; D054817:Pollination
chemical_list: D005030:Ethylenes; D005875:Gibberellins; D010937:Plant Growth Regulators; C036216:ethylene
keywords: Solanum lycopersicum; auxin; ethylene; fruit set; gibberellin; parthenocarpy