Abstract
BackgroundOvule lifespan is an important factor in determining the ability to set fruits and produce seeds. Once ovule senescence is established, fruit set capacity in response to gibberellins (GAs) is lost. We aimed to elucidate whether ethylene plays a role in controlling ovule senescence and the fruit set response in Arabidopsis.ResultsEthylene response inhibitors, silver thiosulphate (STS) and 1-methylcyclopropene (1-MCP), were able to delay the loss of pistil response to GA3. In addition, ethylene insensitive mutants ein2-5 and ein3-1 showed delayed loss of pistil response, as in plants treated with STS and 1-MCP, while constitutive mutant ctr1-1 displayed premature loss of response. The analysis of the expression of ethylene biosynthesis genes suggests that ethylene is synthesised in ovules at the onset of ovule senescence, while a transcriptional meta-analysis also supports an activated ethylene-dependent senescence upon the establishment of ovule senescence. Finally, a SAG12:GUS reporter line proved useful to monitor ovule senescence and to directly demonstrate that ethylene specifically modulates ovule senescence.ConclusionsWe have shown that ethylene is involved in both the control of the ovule lifespan and the determination of the pistil/fruit fate. Our data support a role of the ovule in modulating the GA response during fruit set in Arabidopsis. A possible mechanism that links the ethylene modulation of the ovule senescence and the GA3-induced fruit set response is discussed.
Highlights
Ovule lifespan is an important factor in determining the ability to set fruits and produce seeds
Ethylene signalling modulates pistil responsiveness to GAs To test whether ethylene plays a role in pistil responsiveness to GAs, we first used two inhibitors of ethylene action, silver thiosulphate (STS) and 1-methylcyclopropene (1-MCP) to check if they affect the elongation triggered by gibberellic acid (GA3) when applied to unpollinated pistils
Inhibition of ethylene action postponed the loss of pistil fruit set responsiveness to GA3 by about 1 day (Figure 1)
Summary
Ovule lifespan is an important factor in determining the ability to set fruits and produce seeds. Once ovule senescence is established, fruit set capacity in response to gibberellins (GAs) is lost. We aimed to elucidate whether ethylene plays a role in controlling ovule senescence and the fruit set response in Arabidopsis. Pistils become mature fruits by following a complex developmental programme triggered by ovule fertilisation, and by the hormonal signal cascade that follows. In the absence of this triggering event, the pistil’s autonomous developmental programme leads to organ senescence after a few days [1,2,3,4]. We showed that the development of the Arabidopsis unfertilised pistil differs from that of pea since the Arabidopsis ovary wall shows developmental characteristics that are shared with a developing fruit, while senescence is established first at the stigma, and progresses from basal to apical ovules [4]
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