AUXIN RESPONSE FACTOR 2 Intersects Hormonal Signals in the Regulation of Tomato Fruit Ripening

Abstract

The involvement of ethylene in fruit ripening is well documented, though knowledge regarding the crosstalk between ethylene and other hormones in ripening is lacking. We discovered that AUXIN RESPONSE FACTOR 2A (ARF2A), a recognized auxin signaling component, functions in the control of ripening. ARF2A expression is ripening regulated and reduced in the rin, nor and nr ripening mutants. It is also responsive to exogenous application of ethylene, auxin and abscisic acid (ABA). Over-expressing ARF2A in tomato resulted in blotchy ripening in which certain fruit regions turn red and possess accelerated ripening. ARF2A over-expressing fruit displayed early ethylene emission and ethylene signaling inhibition delayed their ripening phenotype, suggesting ethylene dependency. Both green and red fruit regions showed the induction of ethylene signaling components and master regulators of ripening. Comprehensive hormone profiling revealed that altered ARF2A expression in fruit significantly modified abscisates, cytokinins and salicylic acid while gibberellic acid and auxin metabolites were unaffected. Silencing of ARF2A further validated these observations as reducing ARF2A expression let to retarded fruit ripening, parthenocarpy and a disturbed hormonal profile. Finally, we show that ARF2A both homodimerizes and interacts with the ABA STRESS RIPENING (ASR1) protein, suggesting that ASR1 might be linking ABA and ethylene-dependent ripening. These results revealed that ARF2A interconnects signals of ethylene and additional hormones to co-ordinate the capacity of fruit tissue to initiate the complex ripening process.

Nitric Oxide Overproduction in Tomato shr Mutant Shifts Metabolic Profiles and Suppresses Fruit Growth and Ripening

“…Such a cross talk has been recently reported in developing tomato fruits where AUXIN RESPONSE FACTOR 2A homodimerizes with ABA STRESS RIPENING (ASR1) protein, thus linking ABA and ethylene-dependent ripening. (Breitel et al, 2016). …”

Ethylene Role in Plant Growth, Development and Senescence: Interaction with Other Phytohormones

“…The equilibrium between ethylene and auxin is crucial for the regulation of leaf abscission. During leaf senescence, the auxin concentration declined and tissue sensitivity to ethylene increased as well as ethylene biosynthesis (Brown, 1997). Using a transcriptome approach, 1,088 transcription factors (TFs) were found to be differentially regulated in the soybean leaf abscission.…”

“…The application of auxin lowered the ethylene production in sliced apples ( Malus domestica ), if applied at pre-climacteric phase, while enhancing its biosynthesis at the climacteric stage (Lieberman et al, 1977). The transcription factor AUXIN RESPONSE FACTOR 2A (ARF2A) has been recognized as an auxin signaling component and was able to control ripening (Breitel et al, 2016). There exists a crosstalk between auxin and ethylene; and Bleecker and Kende (2000) pointed out that auxins can stimulate the biosynthesis of more climacteric ethylene through its inductive action on the expression of the key enzyme ACS (Abel and Theologis, 1996).…”

MYB107 and MYB9 Homologs Regulate Suberin Deposition in Angiosperms

“…Hormone extraction was performed as previously described (Kojima et al, 2009;Dobrev and Vankova, 2012;Breitel et al, 2016) with some modifications. Briefly, 10 mg of ground frozen dry seeds were extracted at 220°C with methanol/water/formic acid, containing stable isotope-labeled internal standards.…”