Key Message

Cytokinin together with MdoBRR1, MdoBRR8 and MdoBRR10 genes participate in the downregulation of MdoDAM1, contributing to the transition from endo- to ecodormancy in apple buds.

Abstract

The final step of cytokinin (CK) signaling pathway culminates in the activation of type-B response regulators (BRRs), important transcriptional factors in the modulation of CK-responsive genes. In this study, we performed a genome-wide analysis aiming to identify apple BRR family members and understand their involvement in bud dormancy control. The investigation identified ten MdoBRR protein-coding genes. A higher expression of three MdoBRR (MdoBRR1, MdoBRR9 and MdoBRR10) was observed in dormant buds in comparison to other developmental stages. Interestingly, in ecodormant buds these three MdoBRR genes were upregulated in a CK-dependent manner. Transcription profiles, determined during dormancy cycle under field and artificially controlled conditions, revealed that MdoBRR1 and MdoBRR8 played important roles in the transition from endo- to ecodormancy, probably mediated by endogenous CK stimuli. The expression of MdoBRR7, MdoBRR9, and MdoBRR10 was induced in ecodormant buds exposed to warm temperatures, indicating a putative role in growth resumption after chilling requirement fulfillment. Contrasting expression patternsin vivo between MdoBRRs and MdoDAM1, an essential dormancy establishment regulator, were observed during dormancy cycle and in CK-treated buds. Thereafter, in vivo transactivation assays showed that CK stimuli combined with transient overexpression of MdoBRR1, MdoBRR8, and MdoBRR10 resulted in downregulation of the reporter gene gusA driven by the MdoDAM1 promoter. These pieces of evidences point to the integration of CK-triggered responses through MdoBRRs that are able to downregulate MdoDAM1, contributing to dormancy release in apple.

中文翻译：

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B 型细胞分裂素反应调节剂在苹果芽从内休眠到生态休眠的过渡过程中将激素刺激和分子反应联系起来。

关键信息

细胞分裂素与MdoBRR1、MdoBRR8和MdoBRR10基因一起参与 MdoDAM1 的下调，有助于苹果芽从内休眠到生态休眠的转变。

抽象的

细胞分裂素 (CK) 信号通路的最后一步是激活 B 型反应调节因子 (BRR)，这是调节 CK 反应基因的重要转录因子。在这项研究中，我们进行了一项全基因组分析，旨在识别苹果BRR家族成员并了解他们参与芽休眠控制的过程。调查确定了十个MdoBRR蛋白编码基因。与其他发育阶段相比，在休眠芽中观察到三种MdoBRR（MdoBRR1、MdoBRR9和MdoBRR10 ）的更高表达。有趣的是，在生态休眠芽中，这三个MdoBRR基因以 CK 依赖性方式上调。在田间和人为控制条件下的休眠周期中确定的转录谱表明，MdoBRR1和MdoBRR8在从内休眠到生态休眠的转变中发挥了重要作用，可能是由内源性 CK 刺激介导的。MdoBRR7、MdoBRR9和MdoBRR10的表达在暴露于温暖温度的生态休眠芽中被诱导，表明在满足低温要求后其在生长恢复中的推定作用。对比MdoBRRs和MdoDAM1 的体内表达模式，在休眠周期和 CK 处理的芽中观察到一种重要的休眠建立调节剂。此后，体内反式激活测定显示CK刺激与MdoBRR1、MdoBRR8和MdoBRR10的瞬时过表达相结合导致由MdoDAM1启动子驱动的报告基因gusA的下调。这些证据表明 CK 触发的反应通过能够下调MdoDAM1的 MdoBRR 进行整合，从而有助于苹果的休眠释放。