Ethylene suppresses tomato (Solanum lycopersicum) fruit set through modification of gibberellin metabolism

Abstract

SUMMARYFruit 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.

Suppression of DELLA signaling induces procambial cell formation in culture

“…The samples were harvested and frozen in liquid nitrogen at the indicated time points. The GAs were quantified with ultra‐high performance liquid chromatography (UHPLC)‐electrospray interface (ESI) and quadrupole‐orbitrap mass spectrometry (UHPLC/Q‐Exactive; Thermo Scientific) using an ODS column (AQUITY UPLC BEH C18 1.7 μm, 2.1 × 100 mm, Waters, http://www.waters.com/) as described previously (Kojima et al ., ; Shinozaki et al ., ).…”

Temporal and spatial changes in gene expression, metabolite accumulation and phytohormone content in rice seedlings grown under drought stress conditions

“…GC‐MS analysis was performed using a previously described system (Avin‐Wittenberg et al ., ), comprising a CTC CombiPAL autosampler (http://www.ctc.ch/), an Agilent 6890N gas chromatograph (http://agilent.com./) and a LECO Pegasus III TOF‐MS (http://www.leco.com/). LC‐MS analysis was performed as described previously (Kojima et al ., ; Shinozaki et al ., ) using an LC‐MS system (AQUITY UPLC System/XEVO‐TQS; Waters, http://www.waters.com/) with an ODS column (AQUITY UPLC HSS T3, 1.8 μm, 2.1 × 100 mm; Waters) for cytokinins and an ultra‐high‐performance liquid chromatography‐Q‐Exactive™ system (Thermo Scientific, https://www.thermofisher.com/) with an ODS column (AQUITY UPLC BEH C18, 1.7 μm, 2.1 × 100 mm; Waters) for other metabolites. The Roche Yellow line Maltose/Sucrose/D‐Glucose assay kit (r‐Biopharm, http://www.r-biopharm.com/) was also employed for the glucose quantification.…”

Wounding Triggers Callus Formation via Dynamic Hormonal and Transcriptional Changes

“…Contents of cytokinins were quantified with ultra-performance liquid chromatography-electrospray interface and tandem quadrupole mass spectrometer (AQUITY UPLC System/Xevo-TQS; Waters) as described previously (Kojima et al, 2009). Auxin, JA, and ABA were quantified with ultra-high-performance liquid chromatography (HPLC)-electrospray interface and quadrupole-orbitrap mass spectrometer (UHPLC/Q-Exactive; Thermo Scientific) as described previously Shinozaki et al, 2015).…”