The Effect of 1-MCP on the Expression of Carotenoid, Chlorophyll Degradation, and Ethylene Response Factors in ‘Qihong’ Kiwifruit

The development of yellow color is an important aspect of fruit quality in yellow fleshed kiwifruit during fruit ripening, and it has a large influence on consumer preference. The yellow color is determined by carotenoid accumulation and chlorophyll degradation and is likely affected by ethylene production. This study investigates the expression of carotenoid, chlorophyll degradation, and ethylene response factors in ‘Qihong’ fruit, which had reached the near ripening stage (firmness ≈ 20 N) and were either left untreated (controls) or treated with 0.5 μL L−1 of 1-MCP for 12 h. Both the accumulation of β-carotene (not lutein) and degradation of chlorophyll a and b increased in response to the 1-MCP treatment, resulting in more yellow colored flesh in the 1-MCP treated fruit with higher carotenoid and lower chlorophyll contents. 1-MCP up-regulated AcLCY-β, AcSGR1, and AcPAO2, but reduced the expression of AcCCD1. These four genes were correlated with the concentrations of β-carotene and the chlorophylls. The expression of three ethylene response factors, including Acc29730, Acc25620, and Acc23763 were delayed and down-regulated in 1-MCP treated fruit, showing the highest correlation with the expression of AcLCY-β, AcSGR1, AcPAO2, and AcCCD1. Dual-Luciferase assays showed that 1-MCP treatment not only eliminated the inhibition of Acc23763 on the promoters of both AcPAO2 and AcLCY-β, but also reduced the activation of Acc29730 and Acc25620 on the AcCCD1 promoter. Our findings indicate that Acc29730, Acc25620, and Acc23763 may play an important role in the response to 1-MCP treatment during the fruit eating ripe stage, which likely altered the promoter activities of carotenoid and chlorophyll-related genes (AcPAO2, AcLCY-β and AcCCD1) to regulate their transcripts, resulting in more yellow color in the fruit flesh of ‘Qihong’.

The Transcription Factor HcERF4 Confers Salt and Drought Tolerance in Kenaf (Hibiscus Cannabinus L.)

Ethylene response factors (ERF) are members of the APETALA2/ERF transcription factor family, and they play an important role in plant growth, development, and response to various environmental stresses. In the present study, an ERF transcription factor HcERF4 was isolated and characterized from kenaf. The protein encoded by the HcERF4 has 233 amino acid residues with a theoretical isoelectric point of 8.89 and a predicted molecular weight of 25.53 kDa. HcERF4 had an over than 86.97% identity to HsERF4(XP_039019980.1), and shared a closest phylogenetic relationship with Hibiscus syriacus. Subcellular localization analysis shows that HcERF4 is located in the nucleus. Transactivation assays in yeast demonstrated that HcERF4 functions as a transcriptional activator. The expression of HcERF4 was enriched in leaf and root, and can be induced by salt or drought treatments in kenaf. The VIGS-silenced HcERF4 plant showed significantly reduced plant height, stem diameter, fresh weight, and relative water content (RWC) compared with wild type plants under salt or drought stress condition; In addition, the contents of MDA, O2−, H2O2, and free proline is significantly increased, and the activities of SOD and CAT are significantly reduced. The DAB/NBT staining results showed that the H2O2 and O2− contents in HcERF4-silenced plants were consistent with the determination. Based on these results, it is proposed that HcERF4 plays an important role in regulating salt and drought stress in kenaf.

Genome-wide identification and functional analysis of the ERF2 gene family in response to disease resistance against Stemphylium lycopersici in tomato

Background APETALA2/ethylene responsive factor (AP2/ERF) transcription factors are a plant-specific family of transcription factors and one of the largest families of transcription factors. Ethylene response factors (ERF) regulate plant growth, development, and responses to biotic and abiotic stress. In a previous study, the ERF2 gene was significantly upregulated in both resistant and susceptible tomato cultivars in response to Stemphylium lycopersici. The main purpose of this study was to systematically analyze the ERF family and to explore the mechanism of ERF2 in tomato plants resisting pathogen infection by the Virus-induced Gene Silencing technique. Results In this experiment, 134 ERF genes were explored and subjected to bioinformatic analysis and divided into twelve groups. The spatiotemporal expression characteristics of ERF transcription factor gene family in tomato were diverse. Combined with RNA-seq, we found that the expression of 18 ERF transcription factors increased after inoculation with S. lycopersici. In ERF2-silenced plants, the susceptible phenotype was observed after inoculation with S. lycopersici. The hypersensitive response and ROS production were decreased in the ERF2-silenced plants. Physiological analyses showed that the superoxide dismutase, peroxidase and catalase activities were lower in ERF2-silenced plants than in control plants, and the SA and JA contents were lower in ERF2-silenced plants than in control plants after inoculation with S. lycopersici. Furthermore, the results indicated that ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance. Conclusions In this study, we identified and analyzed members of the tomato ERF family by bioinformatics methods and classified, described and analyzed these genes. Subsequently, we used VIGS technology to significantly reduce the expression of ERF2 in tomatoes. The results showed that ERF2 had a positive effect on tomato resistance to S. lycopersici. Interestingly, ERF2 played a key role in multiple SA, JA and ROS signaling pathways to confer resistance to invasion by S. lycopersici. In addition, ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance to S. lycopersici. In summary, this study provides gene resources for breeding for disease resistance in tomato.

Genome-wide identification and function analysis of ERF2 gene family in response to disease resistance against Stemphylium lycopersici in tomato

Background: APETALA2/ethylene responsive factor (AP2/ERF) transcription factors are a plant-specific family of transcription factors and one of the largest families of transcription factors. Ethylene response factors (ERF) regulate plant growth, development, and responses to biotic and abiotic stress. In a previous study, the ERF2 gene was significantly upregulated in both resistant and susceptible tomato cultivars in response to Stemphylium lycopersici. The main purpose of this study was to systematically analyze the ERF family and to explore the mechanism of ERF2 in tomato plants resisting pathogen infection by the Virus-induced Gene Silencing (VIGS) technique.Results: In this experiment, 134 ERF genes were explored and subjected to bioinformatic analysis. This experiment divided 134 ERF members into twelve groups based on the conserved domain of the genes. The spatiotemporal expression characteristics of ERF transcription factor family genes in tomato were diverse. Combined with RNA-seq, we found that the expression of 18 ERF transcription factors increased after inoculation with S. lycopersici. In ERF2-silenced plants, the susceptible phenotype was observed after inoculation with S. lycopersici. The hypersensitive response and ROS production were decreased in the ERF2-silenced plants. Physiological analyses showed that the superoxide dismutase, peroxidase and catalase activities were lower in ERF2-silenced plants than in control plants, and the SA and JA contents were lower in ERF2-silenced plants than in control plants after inoculation with S. lycopersici. Furthermore, the results indicated that ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance.Conclusions: In this study, we identified and analyzed members of the tomato ERF family by bioinformatics methods and classified, described and analyzed these genes. Subsequently, we used VIGS technology to significantly reduce the expression of ERF2 in tomatoes. The results showed that ERF2 had a positive effect on tomato resistance to S. lycopersici. Interestingly, ERF2 played a key role in multiple SA, JA and ROS signaling pathways to confer resistance to invasion by S. lycopersici. In addition, ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance to S. lycopersici. In summary, this study provides gene resources for breeding for disease resistance in tomato.

Molecular basis for cysteine oxidation by Plant Cysteine Oxidases from Arabidopsis thaliana

Plant Cysteine Oxidases (PCOs) play important roles in controlling the stability of Group VII ethylene response factors (ERF-VIIs) via N-Arg/degron pathway through catalyzing the oxidation of their N-Cys for subsequent Arginyl-tRNA--protein transferase 1 (ATE1) mediated arginine installation. Here we presented structures of PCO2, PCO4, and PCO5 from Arabidopsis thaliana (AtPCOs) and examined their in vitro activity by MS. On the basis of Tris-bound AtPCO2, we modelled the Cys-bound AtPCO2 structure and identified key residues involved in N-Cys oxidation. Alanine substitution of potential N-Cys interaction residues impaired the activity of AtPCO5 remarkably. The structural research, complemented by mutagenesis and mass spectrometry experiments, not only uncovers the substrate recognition and catalytic mode by AtPCOs, but also sheds light on the future design of potent inhibitors for plant cysteine oxidases.

An AP2/ERF Gene, HuERF1, from Pitaya (Hylocereus undatus) Positively Regulates Salt Tolerance

Pitaya (Hylocereus undatus) is a high salt-tolerant fruit, and ethylene response factors (ERFs) play important roles in transcription-regulating abiotic tolerance. To clarify the function of HuERF1 in the salt tolerance of pitaya, HuERF1 was heterogeneously expressed in Arabidopsis. HuERF1 had nuclear localization when HuERF1::GFP was expressed in Arabidopsis protoplasts and had transactivation activity when HuERF1 was expressed in yeast. The expression of HuERF1 in pitaya seedlings was significantly induced after exposure to ethylene and high salinity. Overexpression of HuERF1 in Arabidopsis conferred enhanced tolerance to salt stress, reduced the accumulation of superoxide (O2 · ¯ ) and hydrogen peroxide (H2O2), and improved antioxidant enzyme activities. These results indicate that HuERF1 is involved in ethylene-mediated salt stress tolerance, which may contribute to the salt tolerance of pitaya.