SnRK2 subfamily I protein kinases regulate ethylene biosynthesis by phosphorylating HB transcription factors to induce ACO1 expression in apple

第一作者：Meiru Jia

第一单位：中国农业大学

第一通讯：Wensuo Jia

 Abstarct 

背景+问题：Ethylene controls climacteric fruit ripening and can be triggered by osmotic stress. However, the mechanism regulating ethylene biosynthesis during fruit ripening and under osmotic stress is largely unknown in apple (Malus domestica). 

乙烯控制跃变型果实的成熟，并且会受到渗透胁迫的诱导。但是，苹果果实在成熟过程中和在渗透胁迫下的乙烯生物合成调控机制尚不清楚。

主要发现：Here, we explored the roles of SnRK2 protein kinases in ethylene biosynthesis related to fruit ripening and osmoregulation. We identified the substrates of MdSnRK2-I using phosphorylation analysis techniques. Finally, we identified the MdSnRK2-I-mediated signaling pathway for ethylene biosynthesis related to fruit ripening and osmoregulation. 

本文中，作者研究了SnRK2蛋白激酶在果实成熟中和渗透胁迫下，作用于乙烯生物的功能。作者利用磷酸化分析的技术，鉴定到了MdSnRK2-I的底物。最后，作者鉴定了由MdSnRK2-I介导的信号通路，该通路作用于苹果果实成熟和渗透胁迫下的乙烯生物合成调控。

结果1-MdSnRK2-I表达模式与过表达表型：The activity of two MdSnRK2-I members, MdSnRK2.4 and MdSnRK2.9, was significantly upregulated during ripening or following mannitol treatment. Overexpression of MdSnRK2-I increased ethylene biosynthesisunder normal and osmotic conditions in apple fruit. 

在果实成熟过程中，或者在用甘露醇处理之后，MdSnRK2-I的两个成员MdSnRK2.4和MdSnRK2.9的活性被显著上调。过表达MdSnRK2-I基因能够增强苹果果实在正常和渗透胁迫下的乙烯生物合成。

结果2-MdSnRK2-I间接促进ACO1表达和直接促进ACS1蛋白稳定：MdSnRK2-I phosphorylated the transcription factors MdHB1 and MdHB2 to enhance their protein stability and transcriptional activity on MdACO1. MdSnRK2-I also interacted with MdACS1 and increased its protein stability through two phosphorylation sites. The increased MdACO1 expression and MdACS1 protein stability resulted in higher ethylene production in apple fruit. 

MdSnRK2-I磷酸化转录因子MdHB1和MdHB2，增强其蛋白稳定性及其作用于MdACO1的转录活性。MdSnRK2-I还能够与MdACS1互作，通过两个磷酸化位点增强MdACS1蛋白稳定性。MdACO1基因表达量的增加和MdACS1蛋白稳定性的增强，共同作用于苹果果实更高的乙烯产量。

结果3-SnRK2-I在苹果和番茄中的功能保守性：Additionally, heterologous expression of MdSnRK2-I or manipulation of SlSnRK2-I expression in tomato (Solanum lycopersicum) fruit altered fruit ripening and ethylene biosynthesis.

另外，在番茄果实中异源表达苹果的MdSnRK2-I基因，或者是控制番茄本身SlSnRK2-I基因的表达，能够影响番茄果实的成熟和乙烯的生物合成。

结论：We established that MdSnRK2-I functions in fruit ripening and osmoregulation, and identified the MdSnRK2-I-mediated signaling pathway controlling ethylene biosynthesis.

本文的研究结果揭示了苹果MdSnRK2-I作用于果实成熟和渗透胁迫的功能，并且解析了MdSnRK2-I介导的乙烯生物合成调控的信号通路。

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doi: https://doi.org/10.1111/nph.18040

Journal: New Phytologist

Published date: February 19, 2022