Ethylene receptors signal via a non-canonical pathway to regulate abscisic acid responses

Corresponding author: Brad Binder

Ethylene is a gaseous (气态的) plant hormone perceived (感知) by a family of receptors in Arabidopsis thaliana including ETHYLENE RESPONSE1 (ETR1) and ETR2. Previously we showed that etr1-6 loss-of-function plants germinate (发育) better and etr2-3 loss-of-function plants germinate worse than wild-type under NaCl stress and in response to abscisic acid (ABA). In this study, we expanded these results by showing that ETR1 and ETR2 have contrasting (不同的) roles in the control of germination under a variety of inhibitory conditions (抑制条件) for seed germination such as treatment with KCl, CuSO4, ZnSO4, and ethanol (乙醇). Pharmacological (药理学) and molecular biology results support a model where ETR1 and ETR2 are indirectly affecting the expression of genes encoding ABA signaling proteins to affect ABA sensitivity. The receiver domain of ETR1 is involved in this function in germination under these conditions and controlling the expression of genes encoding ABA signaling proteins. Epistasis analysis (上位性分析) demonstrated that these contrasting roles of ETR1 and ETR2 do not require the canonical (经典的) ethylene signaling pathway. To explore the importance of receptor-protein interactions we conducted yeast two-hybrid screens using the cytosolic (细胞溶质的) domains of ETR1 and ETR2 as bait. Unique interacting partners with either ETR1 or ETR2 were identified. We focused on three of these proteins and confirmed the interactions with receptors. Loss of these proteins led to faster germination in response to ABA showing that they are involved in ABA responses. Thus, ETR1 and ETR2 have both ethylene-dependent and -independent roles in plant cells that affect responses to ABA.

乙烯是气态的植物激素，拟南芥中包括ETR1和ETR2在内的一个家族的受体会感知乙烯这个植物激素。作者先前的研究表明在NaCl胁迫和响应ABA处理中，etr1-6功能缺失突变体要比野生型萌发更好，而etr2-3功能缺失突变体要比野生型萌发更差。本文的研究显示在诸如KCl、CuSO4、ZnSO4和乙醇等胁迫处理种子萌发下，ETR1和ETR2对于萌发具有相反的作用。药理学和分子生物学的结果显示ETR1和ETR2会直接影响ABA信号转导相关基因的表达以影响植株的ABA敏感性。ETR1的接受结构域在胁迫处理下参与了ETR1介导萌发的功能发挥，并控制ABA信号转导基因的表达。上位性分析表明ETR1和ETR2相反的功能与经典的乙烯信号通路并不相关联。作者利用ETR1和ETR2的胞质结构域作为bait进行了酵母双杂试验以进一步探索受体蛋白互作的重要性。作者鉴定了一些与ETR1或ETR2特异互作的组分。作者着重关注了其中三个蛋白，并进一步确认了其与受体的互作。这些蛋白缺失会导致在响应ABA条件下萌发更快，表明这些蛋白在ABA响应中起作用。因此，ETR1和ETR2在植物细胞中同时具有依赖乙烯和独立于乙烯两种功能，进而影响植物的ABA响应。

研究方向： 乙烯信号转导机制。

doi: https://doi.org/10.1104/pp.17.01321