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.

中文翻译：

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转录因子 Constans-like 4 可能通过与脱落酸和乙烯信号传导相互作用来调节番茄果实成熟


植物激素对番茄成熟至关重要，据推测，脱落酸 （ABA） 可在番茄果实成熟开始时诱导乙烯生物合成;然而，它的交互地点仍不清楚。在本研究中，从番茄果实中克隆了 CO/COL 转录因子 Constans-like 4 （SlCOL4）。氨基酸序列和亚细胞定位分析证明，SlCOL4 是 COL 家族的典型转录因子。基因表达分析显示，SlCOL4 在番茄植株的不同组织中表达，其转录丰度在果实成熟开始时下降，巧合的是，它在 ABA 处理的番茄果实中下调，并在处理后 6 h 内对外源 ABA 有反应。同时，酵母单杂交双荧光素酶分析显示，ABA 反应因子 SlAREB1 抑制了 SlCOL4 的转录，表明它在番茄果实成熟绿色阶段受到 ABA 的直接调控此外，果皮颜色变红的速度比对照果实快，乙烯生物合成关键基因 ACS2、ACS4 和 ACO1， 在 SlCOL4 沉默的番茄果实中上调，表明 SlCOL4 可能是成熟的负调节因子。此外，通过染色质免疫沉淀测序 （ChIP-Seq） 分析，在 SlCOL4 的下游鉴定了几个与乙烯信号通路相关的基因。总体而言，转录因子 SlCOL4 可能与 ABA 和乙烯信号相互作用，并负向调节番茄果实的成熟。本研究结果为阐明 ABA-乙烯相互作用调控番茄果实成熟的分子机制提供了新的见解，并为进一步研究 COLs 转录因子在番茄果实成熟中的作用提供了参考。