SlAREB1, a member of the abscisic acid (ABA) response element-binding factors (AREB/ABFs) family, was reported to play a crucial role in the expression of ABA-regulated downstream genes and affect the ripening of tomato fruit. However, the downstream genes ofSlAREB1are still unclear. Chromatin immunoprecipitation (ChIP) is a powerful tool and a standard method for studying the interactions between DNA and proteins at the genome-wide level. In the present study,SlAREB1was proved to continually increase until the mature green stage and then decrease during the ripening period, and a total of 972 gene peaks were identified downstream ofSlAREB1by ChIP-seq analysis, mainly located in the intergenic and promoter regions. Further gene ontology (GO) annotation analysis revealed that the target sequence ofSlAREB1was the most involved in biological function. Kyoto Encylopaedia of Genes and Genomes (KEGG) pathway analysis showed that the identified genes were mainly involved in the oxidative phosphorylation and photosynthesis pathways, and some of them were associated with tomato phytohormone synthesis, the cell wall, pigment, and the antioxidant characteristic of the fruit as well. Based on these results, an initial model ofSlAREB1regulation on tomato fruit ripening was constructed, which provided a theoretical basis for further exploring the effects of the regulation mechanism ofSlAREB1and ABA on tomato fruit ripening.Keywords:tomato;abscisic acid;SlAREB1transcription factor;ChIP-Seq;fruit ripening
Jianghui Huang,Qiong Wu,Yanan He,Dongdong Zhang,Yurong Zhang,Xiaoya Tao
Ethylene biosynthesis during postharvest ripening of tomato fruit is stimulated by the phytohormone abscisic acid (ABA). This research utilized mature green cherry tomato fruit to elucidate the molecular mechanism of SlAREB1 regulating ethylene biosynthesis and mediating ABA’s effect on postharvest ripening of tomato fruit. Results indicated that ABA treatment expedited alterations in fruit color, firmness, ethylene release rate, and modulated the expression of SlAREB1 and genes associated with ethylene biosynthesis. Meanwhile, SlAREB1 was proven to participate in the regulatory process of ABA on tomato fruit ripening. The results of yeast one-hybrid and dual luciferase assays demonstrated that SlAREB1 interacted with the promoters of ACS2, ACO1, FUL1, and MADS1, and activated their transcriptions, thereby regulating ethylene biosynthesis and subsequently affecting the ripening process of postharvest tomato fruit. The molecular model illustrates that SlAREB1 is a downstream component of ABA signaling that directly regulates ethylene-related genes, thereby mediating ABA’s effect. These findings provide a theoretical basis for further improving the regulatory network of hormone interactions during tomato fruit ripening.
Qiong Wu,Xiaoya Tao,Chunxiao Cui,Yanan He,Dongdong Zhang,Yurong Zhang,Li Li
Phytohormones are vital for tomato ripening, and abscisic acid (ABA) is speculated to induce ethylene biosynthesis at the initiate of tomato fruit ripening; however, its interaction sites remain unclear. In the present study, Constans-like 4 (SlCOL4), a CO/COL transcription factor, was cloned from tomato fruit. Amino acid sequence and subcellular location analysis proved that SlCOL4 was a typical transcription factor of the COL family. Gene expression analysis showed SlCOL4 expressed in different tissues of tomato plants and its transcription abundance declined at the onset of fruit ripening, coincidentally it was found to be down-regulated in ABA-treated tomato fruit and responded to exogenous ABA within 6 h after treatment. Meanwhile, yeast one-hybrid and dual-luciferase analysis showed that the ABA response factor SlAREB1 inhibited the transcription of SlCOL4 , indicating it was directly regulated by ABA at the mature green stage of tomato fruit . In addition, the pericarp color turned red faster than that of control fruit, and the key ethylene biosynthesis genes, ACS2, ACS4, and ACO1 , were up-regulated in SlCOL4 silenced tomato fruit, suggesting that SlCOL4 may be a negative regulator of ripening. Furthermore, several genes associated with the ethylene signaling pathway were identified downstream of SlCOL4 by chromatin immunoprecipitation sequencing (ChIP-Seq) analysis. Overall, the transcription factor SlCOL4 may interact with ABA and ethylene signals and negatively regulate tomato fruit ripening. The results in this study provide new insights for elucidating the molecular mechanism of ABA-ethylene interaction in regulating tomato fruit ripening, and provide references for further research on the role of COLs transcription factors in tomato fruit ripening as well.
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