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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Plant, Soil and Nutrition Research » Research » Publications at this Location » Publication #322507

Title: Ethylene suppresses tomato (solanum lycopersicum) fruit set through modification of gibberellin metabolism

item SHINOZAKI, YOSHIHITO - University Of Tsukuba
item HAO, SHUHEI - University Of Tsukuba
item KOJIMA, MIKIKO - University Of Tsukuba
item ZHENG, YI - Boyce Thompson Institute
item FEI, ZHANGJUN - Boyce Thompson Institute
item ZHONG, SILIN - Boyce Thompson Institute
item Giovannoni, James
item ROSE, JOCELYN - Cornell University
item ARIIZUMI, TOHRU - University Of Tsukuba

Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2015
Publication Date: 5/28/2015
Citation: Shinozaki, Y., Hao, S., Kojima, M., Zheng, Y., Fei, Z., Zhong, S., Giovannoni, J.J., Rose, J., Ariizumi, T. 2015. Ethylene suppresses tomato (solanum lycopersicum) fruit set through modification of gibberellin metabolism. Plant Journal. 83:237-251.

Interpretive Summary: 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.

Technical Abstract: The plant hormone ethylene is probably best know as the “ripening hormone”. Ethylene also plays roles in senescence, stress responses and organ shedding (abscission). Regulation of ethylene synthesis, ethylene scavenging and genetic repression of ethylene synthesis and/or signaling are tactics deployed by plant breeders and food storage specialists to reduce or control the impact of this important plant hormone. Here we provide genetic, molecular and hormonal evidence that ethylene also is important in fruit set following pollination, likely through interaction with another plant hormone, GA (gibberellic acid). A better understanding of hormone mediated fruit development will lead to novel strategies to improve hormone mediated processes and in this particular case, improved fruit set which can lead to increased yield.