Abscisic acid (ABA) triggers and regulates, while ethylene modulates autumn leaf senescence. The expression profiles of genes encoding ABA route components and the ACC oxidase isozymes were investigated in Populus tremula during the early and moderate stages of autumn leaf senescence. The targets of interest were Ptre-HAB1-like genes (Ptre-HAB1, Ptre-HAB3a and Ptre-HAB3b), the subclass 3 of Ptre-SnRK2s genes (Ptre-SnRK2.6a, Ptre-SnRK2.6b and Ptre-SnRK2.6b) and Ptre-RbohD1, Ptre-RbohF1, and Ptre-RbohF2 genes encoding the poplar components, which are counterparts of the ABA route key regulators or the counterparts of its secondary messengers, such as Homology to ABA-insensitive 1 (HAB1), Sucrose non-fermenting 1-related protein kinases 2 (SnRK2s) or Respiratory burst oxidase D and Respiratory burst oxidase F (RbohD and RbohF, respectively) in Arabidopsis, and Ptre-ACO3, Ptre-ACO5, and Ptre-ACO6 genes encoding ACC oxidase isozymes involved in ethylene biosynthesis. The fold change in their expression levels enabled to distinguish the distinct expression patterns for the following pairs of genes: Ptre-HAB3a and Ptre-SnRK2.6a, Ptre-HAB3b and Ptre-SnRK2.2, and Ptre-HAB1 and Ptre-SnRK2.6b, where each pair involves the genes encoding the negative and positive regulators of ABA route, respectively. Among the investigated genes, the fold change of expression was the highest for Ptre-ACO3, Ptre-ACO6, and Ptre-SnRK2.6b genes during both the studied stages, and additionally for Ptre-HAB1 and Ptre-RbohD1 genes during the moderate stage. In contrast, the Ptre-RbohF1 and Ptre-RbohF2 genes exhibited only the transient upregulation at the early stage of senescence. In an in vitro study, the ability of protein kinases Ptre-SnRK2.6a and Ptre-SnRK2.6b to phosphorylate the N-terminal regions of Ptre-RbohD1 and Ptre-RbohF2 was studied; the activity of Ptre-SnRK2.6b against the studied Ptre-Rbohs was noticeably lower than that exhibited by Ptre-SnRK2.6a. It seems that despite the high similarity of their polypeptides, Ptre-SnRK2.6a and Ptre-SnRK2.6b may play different biological roles; nonetheless, it requires in vivo confirmation. Surprisingly, the highest protein kinase activity against the Ptre-Rbohs was detected in the heterologous reaction with AT-SnRK2.6/OST1 which suggests that the discussed interactions are evolutionary conserved.

中文翻译：

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杨树衰老叶片中ABA途径组分和ACC氧化酶同工酶基因的表达谱

脱落酸（ABA）触发和调节，而乙烯调节秋叶衰老。在秋叶衰老的早期和中期，在杨树中研究了编码 ABA 途径组分和 ACC 氧化酶同工酶的基因的表达谱。感兴趣的目标是 Ptre-HAB1 样基因（Ptre-HAB1、Ptre-HAB3a 和 Ptre-HAB3b），Ptre-SnRK2s 基因的子类 3（Ptre-SnRK2.6a、Ptre-SnRK2.6b 和 Ptre-SnRK2）。 6b) 和编码杨树成分的 Ptre-RbohD1、Ptre-RbohF1 和 Ptre-RbohF2 基因，它们是 ABA 途径关键调节因子的对应物或其二级信使的对应物，例如与 ABA 不敏感 1 (HAB1) 的同源性，蔗糖非发酵 1 相关蛋白激酶 2 (SnRK2s) 或呼吸爆发氧化酶 D 和呼吸爆发氧化酶 F（RbohD 和 RbohF，分别）在拟南芥中，以及编码参与乙烯生物合成的ACC氧化酶同工酶的Ptre-ACO3、Ptre-ACO5和Ptre-ACO6基因。它们表达水平的倍数变化能够区分以下基因对的不同表达模式：Ptre-HAB3a 和 Ptre-SnRK2.6a、Ptre-HAB3b 和 Ptre-SnRK2.2，以及 Ptre-HAB1 和 Ptre-SnRK2。 6b，其中每一对分别涉及编码 ABA 途径的负调节因子和正调节因子的基因。在所研究的基因中，Ptre-ACO3、Ptre-ACO6 和 Ptre-SnRK2.6b 基因在两个研究阶段的表达倍数变化最高，此外在中等阶段 Ptre-HAB1 和 Ptre-RbohD1 基因的表达倍数变化. 相比之下，Ptre-RbohF1 和 Ptre-RbohF2 基因仅在衰老早期表现出瞬时上调。在一项体外研究中，研究了蛋白激酶 Ptre-SnRK2.6a 和 Ptre-SnRK2.6b 磷酸化 Ptre-RbohD1 和 Ptre-RbohF2 的 N 端区域的能力；Ptre-SnRK2.6b 对研究的 Ptre-Rbohs 的活性明显低于 Ptre-SnRK2.6a。似乎尽管它们的多肽高度相似，但 Ptre-SnRK2.6a 和 Ptre-SnRK2.6b 可能发挥不同的生物学作用；尽管如此，它需要体内确认。令人惊讶的是，在与 AT-SnRK2.6/OST1 的异源反应中检测到针对 Ptre-Rbohs 的最高蛋白激酶活性，这表明所讨论的相互作用在进化上是保守的。6b 对研究的 Ptre-Rbohs 明显低于 Ptre-SnRK2.6a。似乎尽管它们的多肽高度相似，但 Ptre-SnRK2.6a 和 Ptre-SnRK2.6b 可能发挥不同的生物学作用；尽管如此，它需要体内确认。令人惊讶的是，在与 AT-SnRK2.6/OST1 的异源反应中检测到针对 Ptre-Rbohs 的最高蛋白激酶活性，这表明所讨论的相互作用在进化上是保守的。6b 对研究的 Ptre-Rbohs 明显低于 Ptre-SnRK2.6a。似乎尽管它们的多肽高度相似，但 Ptre-SnRK2.6a 和 Ptre-SnRK2.6b 可能发挥不同的生物学作用；尽管如此，它需要体内确认。令人惊讶的是，在与 AT-SnRK2.6/OST1 的异源反应中检测到针对 Ptre-Rbohs 的最高蛋白激酶活性，这表明所讨论的相互作用在进化上是保守的。