背景+问题：Soluble sugar accumulation in fruit ripening determines fleshy fruit quality. However, the molecular mechanism for this process is not yet understood. 

主要发现：Here, we showed a transcriptional repressor, CmMYB44, regulates sucrose accumulation and ethylene synthesis in oriental melon (Cucumis. melo var. makuwa Makino) fruit. 

结果1-CmMYB44-蔗糖/乙烯：Overexpressing CmMYB44 suppressed sucrose accumulation and ethylene production. 

结果2-CmMYB44-CmSPS1/CmACO1：Furthermore, CmMYB44 repressed the transcriptional activation of CmSPS1 (sucrose phosphate synthase 1)and CmACO1 (ACC oxidase 1), two key genes in sucrose and ethylene accumulation, respectively. 

结果3-CmERFI-2-CmMYB44：During the later stages of fruit ripening, the repressive effect of CmMYB44 on CmSPS1 and CmACO1 could be released by overexpressing CmERFI-2 (ethylene response factor I-2) and exogenous ethylene in ‘HS’ fruit (high sucrose accumulation fruit). CmERFI-2 acted upstream of CmMYB44 as a repressor by directly binding the CmMYB44 promoter region, indirectly stimulating the expression level of CmSPS1 and CmACO1. 

结论：Taken together, we provided a molecular regulatory pathway mediated by CmMYB44, which determines the degree of sucrose and ethylene accumulation in oriental melon fruit and sheds light on transcriptional responses triggered by ethylene sensing that enable the process of fruit ripening.

果实成熟过程中可溶性糖的积累决定了果肉品质。然而，这一过程的分子机制尚不清楚。本文中，作者鉴定到了一个转录抑制因子CmMYB44，其调节甜瓜果实中的蔗糖积累和乙烯合成。过表达CmMYB44会抑制蔗糖积累和乙烯产生。此外，CmMYB44分别抑制了蔗糖和乙烯积累的两个关键基因的转录激活，即蔗糖磷酸合酶编码基因CmSPS1和ACC氧化酶编码基因CmACO1。在高糖的甜瓜果实成熟后期，可以通过过表达乙烯响应因子CmERFI-2和外施乙烯，释放CmMYB44对CmSPS1和CmACO1的转录抑制作用。CmERFI-2作为转录抑制因子作用于CmMYB44的上游，直接结合CmMYB44的启动子并抑制其表达，间接促进CmSPS1和CmACO1的表达水平。总之，作者鉴定了一条由CmMYB44介导的分子调控途径，该途径决定了甜瓜果实中蔗糖和乙烯的积累程度，揭示了一个由乙烯感知诱发的转录响应，从而保证果实的成熟过程。

** 齐红岩 **