Ethylene is a key plant hormone controlling the ripening of climacteric fruits, and several transcription factors acting as important regulators of fruit ripening have been identified in tomato (Solanum lycopersicum), a model for climacteric fruits. The vast majority of these transcription factors are transcriptional activators, however, and the associated transcriptional regulatory mechanisms of most regulators are unclear. Here, we report on a tomato transcriptional repressor (termed SlMYB70) that negatively regulates fruit ripening by directly modulating ethylene biosynthesis. As an EAR motif‐containing MYB transcription factor‐encoding gene, SlMYB70 displayed a ripening‐associated expression pattern and was responsive to ethylene. RNA interference (RNAi)‐mediated repression of SlMYB70 accelerated fruit ripening, but overexpression of SlMYB70 delayed fruit ripening. Ethylene production was noticeably increased and decreased in SlMYB70‐RNAi and SlMYB70‐overexpressing lines, respectively, compared with wild‐type tomatoes. SlMYB70 was proven to be a transcriptional repressor, dependent on the EAR repression motif, and to repress the transcription of two ethylene biosynthesis genes in fruit ripening, namely SlACS2 and SlACO3. The promoters of SlACS2 and SlACO3 are directly bound by SlMYB70, which was verified using a combination of yeast one‐hybrid chromatin immunoprecipitation quantitative polymerase chain reaction and electrophoretic mobility shift assays. These results suggest that SlMYB70 negatively regulates fruit ripening via the direct transcriptional repression of ethylene biosynthesis genes, which provides insights into the ethylene‐mediated key regulatory hierarchy in climacteric fruit ripening, and also highlights different types of transcriptional regulation of fruit ripening.

中文翻译：

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番茄转录阻遏物MYB70直接调节乙烯依赖的果实成熟

乙烯是控制更年期果实成熟的关键植物激素，并且在更年期果实模型番茄（Solanum lycopersicum）中已鉴定出几种转录因子，这些转录因子是果实成熟的重要调节剂。这些转录因子中的绝大多数是转录激​​活因子，但是大多数调节子的相关转录调节机制尚不清楚。在这里，我们报道了一个番茄转录阻遏物（称为SlMYB70），它通过直接调节乙烯的生物合成而负调节水果的成熟。作为含有EAR基序的MYB转录因子编码基因，SlMYB70显示出成熟相关的表达模式，并且对乙烯有反应。RNA干扰（RNAi）介导的抑制SlMYB70加速了果实的成熟，但是SlMYB70的过表达延迟了果实的成熟。乙烯产量明显增加和下降SlMYB70 -RNAi和SlMYB70 -overexpressing线，分别与野生型番茄相比。证实SlMYB70是转录阻遏物，取决于EAR阻遏基序，并且在果实成熟中抑制两个乙烯生物合成基因SlACS2和SlaCO3的转录。SlACS2和SlACO3的启动子与SlMYB70直接结合，结合使用酵母单杂交染色质免疫沉淀定量聚合酶链反应和电泳迁移率变动分析进行验证。这些结果表明，SlMYB70通过乙烯生物合成基因的直接转录阻抑来负调控果实成熟，这为更年期果实成熟中乙烯介导的关键调控体系提供了见解，并且突出了果实成熟的转录调控的不同类型。