Ethylene signaling in plants

Physiology of PSI cyclic electron transport in higher plants Bioenergetics

Inhibitors of protein-protein interactions (PPIs): an analysis of scaffold choices and buried surface area.

Recent advancements in the mechanism of nitric oxide signaling associated with hydrogen sulfide and melatonin crosstalk during ethylene-induced fruit ripening in plants

Ethylene promotes fruit ripening whereas 1-methylcyclopropene (1-MCP), a non-toxic antagonist of ethylene, delays fruit ripening via the inhibition of ethylene receptor. However, unsuitable 1-MCP treatment can cause fruit ripening disorders. In this study, we show that short-term 1-MCP treatment (400 nL•L− 1, 2 h) significantly delays papaya fruit ripening with normal ripening characteristics. However, long-term 1-MCP treatment (400 nL•L− 1, 16 h) causes a “rubbery” texture of fruit. The comparative transcriptome analysis showed that a total of 5529 genes were differently expressed during fruit ripening compared to freshly harvested fruits. Comprehensive functional enrichment analysis showed that the metabolic pathways of carbon metabolism, plant hormone signal transduction, biosynthesis of amino acids, and starch and sucrose metabolism are involved in fruit ripening. 1-MCP treatment significantly affected fruit transcript levels. A total of 3595 and 5998 differently expressed genes (DEGs) were identified between short-term 1-MCP, long-term 1-MCP treatment and the control, respectively. DEGs are mostly enriched in the similar pathway involved in fruit ripening. A large number of DEGs were also identified between long-term and short-term 1-MCP treatment, with most of the DEGs being enriched in carbon metabolism, starch and sucrose metabolism, plant hormone signal transduction, and biosynthesis of amino acids. The 1-MCP treatments accelerated the lignin accumulation and delayed cellulose degradation during fruit ripening. Considering the rubbery phenotype, we inferred that the cell wall metabolism and hormone signal pathways are closely related to papaya fruit ripening disorder. The RNA-Seq output was confirmed using RT-qPCR by 28 selected genes that were involved in cell wall metabolism and hormone signal pathways. These results showed that long-term 1-MCP treatment severely inhibited ethylene signaling and the cell wall metabolism pathways, which may result in the failure of cell wall degradation and fruit softening. Our results reveal multiple ripening-associated events during papaya fruit ripening and provide a foundation for understanding the molecular mechanisms underlying 1-MCP treatment on fruit ripening and the regulatory networks.

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Transcriptomic analysis reveals key factors in fruit ripening and rubbery texture caused by 1-MCP in papaya

Ethylene signaling is decisive for many plant developmental processes. Among these, control of senescence, abscission and fruit ripening are of fundamental relevance for global agriculture. Consequently, detailed knowledge of the signaling network along with the molecular processes of signal perception and transfer are expected to have high impact on future food production and agriculture. Recent advances in ethylene research have demonstrated that signaling of the plant hormone critically depends on the interaction of the ethylene receptor family with the NRAMP-like membrane protein ETHYLENE INSENSITIVE 2 (EIN2) at the ER membrane, phosphorylation-dependent proteolytic processing of ER-localized EIN2 and subsequent translocation of the cleaved EIN2 C‑terminal polypeptide (EIN2-CEND) to the nucleus. EIN2 nuclear transport, but also interaction with the receptors sensing the ethylene signal, both, depend on a nuclear localization signal (NLS) located at the EIN2 C‑terminus. Loss of the tight interaction between receptors and EIN2 affects ethylene signaling and impairs plant ethylene responses. Synthetic peptides derived from the NLS sequence interfere with the EIN2-receptor interaction and have utility in controlling plant ethylene responses such as ripening. Here, we report that a synthetic peptide (NOP-1) corresponding to the NLS motif of Arabidopsis EIN2 (aa 1262-1269) efficiently binds to tomato ethylene receptors LeETR4 and NR and delays ripening in the postharvest phase when applied to the surface of sampled green fruits preharvest. In particular, degradation of chlorophylls was delayed by several days, as monitored by optical sensors and confirmed by analytical methods. Similarly, accumulation of s-carotene and lycopene in the fruit pulp after NOP-1 application was delayed, without having impact on the total pigment concentration in the completely ripe fruits. Likewise, the peptide had no negative effects on fruit quality. Our molecular and phenotypic studies reveal that peptide biologicals could contribute to the development of a novel family of ripening inhibitors and innovative ripening control in climacteric fruit.

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Novel Protein-Protein Inhibitor Based Approach to Control Plant Ethylene Responses: Synthetic Peptides for Ripening Control

The application of artificial light to improve crop production in greenhouses is widely used in the horticultural sector. In this study, we evaluated the impact of light quality on sweet pepper plants’ physiology during a period of water deficit. Pepper plants were cultivated in a climate chamber and exposed to three different light regimes; (compact fluorescent lamps [CFL], continuous intensity from light emitting diodes [LED] [LEDcont] and bell-like shape illumination schedule from LEDs [LEDday]). The effect of temporary water shortage under these light treatments on plant height, chlorophyll and proline concentration, the maximum efficiency of photosystem II (Fv/Fm), the electron transport rate (ETR), and the non-photochemical quenching (NPQ), were studied. In general, plants exposed to CFL showed higher growth rates as compared to those exposed to LED under well-watered conditions. However, the lighting source did not induce significant effects on plant growth and chlorophyll concentration during water deficit, even though proline concentration was higher in plants exposed to CFL and to drought when compared to those exposed to LEDcont and LEDday. LED radiation led to a higher ETR and an early onset of NPQ under water deficit, suggesting an activation of the cyclic electron transport. As outcome, plants grown under LEDcont showed the highest photochemical performance. Overall, the results suggest that pepper plants grown under CFL radiation perform better, even under water deficit, possibly due to the more balanced light spectrum.

Influence of light quality on leaf physiology of sweet pepper plants grown under drought

Background Processes extending the shelf life of climacteric fruit play an important role in terms of a sustainable global food supply. In a previous study, a synthetic octapeptide (NOP-1) was shown to inhibit the interaction between ethylene receptor (ETR) and ethylene insensitive-2 (EIN2), and in consequence delay tomato ripening. We investigated for the first time the effect of NOP-1 on inhibiting the ripening of apples ('Golden Delicious') during postharvest. Results Using purified recombinant proteins from a bacterial expression system, we demonstrate here that EIN2 also interacts tightly (Kd = 136 ± 29 nmol L-1 ) with the corresponding apple ETR MdETR1. In line with previous binding studies on tomato ETRs, the ripening-delaying peptide NOP-1 clearly binds to the purified apple ETR. An NOP-1 solution (1000 µmol L-1 ) was applied with a brush or microdispenser and compared with apples treated with 1-methylcyclopropene (1-MCP) (SmartFresh™, Agrofresh) applied as gaseous treatment or untreated control fruits. NOP-1 inhibited colour development and chlorophyll degradation during shelf life. These effects were more pronounced with the brush application (surface film) than with microdroplets application (mimicking a sprayable formulation). NOP-1 did not alter ethylene release or respiration rate, whereas 1-MCP expectedly strongly suppressed both. There were no differences in quality parameters evaluated. Conclusion Our study shows that NOP-1 binds to MdETR1 which results in delaying of ethylene-dependent ripening developments of skin colour and chlorophyll. Besides application methods, possible reasons for the weak effect of NOP-1 in comparison with previous tomato experiments could be different receptor affinity and penetration differences. © 2019 Society of Chemical Industry.

Influence of the ethylene‐related signal‐inhibiting octapeptide NOP‐1 on postharvest ripening and quality of ‘Golden Delicious’ apples

Ripening inhibitory effect of the ethylene signalling protein EIN2 derived octapeptide NOP-1 on tomatoes as influenced by repeated applications and applications at different ripening stages

Simone Klein

Papers

Novel Protein-Protein Inhibitor Based Approach to Control Plant Ethylene Responses: Synthetic Peptides for Ripening Control

Influence of light quality on leaf physiology of sweet pepper plants grown under drought

Influence of the ethylene‐related signal‐inhibiting octapeptide NOP‐1 on postharvest ripening and quality of ‘Golden Delicious’ apples

Ripening inhibitory effect of the ethylene signalling protein EIN2 derived octapeptide NOP-1 on tomatoes as influenced by repeated applications and applications at different ripening stages