Receptor-like cytoplasmic kinase MARIS functions downstream of CrRLK1L-dependent signaling during tip growth
Receptor-like cytoplasmic kinase MARIS functions downstream of CrRLK1L-dependent signaling during tip growth
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DOI：
10.1073/pnas.1512375112
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发表时间：
2015-09-29
影响因子：
11.1
通讯作者：
Grossniklaus, Ueli
中科院分区：
文献类型：
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作者：
Boisson-Dernier, Aurelien;Franck, Christina Maria;Grossniklaus, Ueli
生长中的植物细胞需要严格协调外部信号与内部过程。例如，维持细胞壁 (CW) 完整性需要协调 CW 传感与 CW 重塑和生物合成，以避免生长停滞或完整性丧失。尽管长春花 RLK1 样 (CrRLK1L) 亚家族的受体样激酶 (RLK) 和产生活性氧的 NADPH 氧化酶参与其中，但这种协调是如何实现的仍然很大程度上未知。 ANXUR1 (ANX1) 和 ANX2 是 CrRLK1L 亚家族的两个冗余成员，是花粉管 (PT) 尖端生长所必需的，它们最接近的同源物 FERONIA 控制根毛尖端生长。此前，我们发现ANX1过表达通过CW物质的过度分泌来轻度抑制PT生长，而anx1 anx2双突变体的花粉管在萌发后自发破裂。在这里，我们报告了通过拯救 anx1 anx2 花粉管破裂而导致育性提高的抑制突变体的鉴定。对其中一个突变体的作图揭示了受体样细胞质激酶 (RLCK) 激活环中的 R240C 非同义取代，我们将其命名为 MARIS (MRI)。我们发现 MRI 是 RLCK-VIII 亚家族的质膜定位成员，并且优先在 PT 和根毛中表达。有趣的是，MRI 敲除突变体表现出自发的 PT 和根毛破裂。此外，MRIR240C突变体的表达，但不是其野生型形式，部分挽救了anx1 anx2 PT和铁根毛的破裂表型，但强烈抑制野生型尖端生长。因此，我们的研究结果确定了 CrRLK1L 依赖性信号级联的一个新的积极成分，可协调 CW 完整性和尖端生长。
Growing plant cells need to rigorously coordinate external signals with internal processes. For instance, the maintenance of cell wall (CW) integrity requires the coordination of CW sensing with CW remodeling and biosynthesis to avoid growth arrest or integrity loss. Despite the involvement of receptor-like kinases (RLKs) of the Catharanthus roseus RLK1-like (CrRLK1L) subfamily and the reactive oxygen species-producing NADPH oxidases, it remains largely unknown how this coordination is achieved. ANXUR1 (ANX1) and ANX2, two redundant members of the CrRLK1L subfamily, are required for tip growth of the pollen tube (PT), and their closest homolog, FERONIA, controls root-hair tip growth. Previously, we showed that ANX1 overexpression mildly inhibits PT growth by over-secretion of CW material, whereas pollen tubes of anx1 anx2 double mutants burst spontaneously after germination. Here, we report the identification of suppressor mutants with improved fertility caused by the rescue of anx1 anx2 pollen tube bursting. Mapping of one these mutants revealed an R240C nonsynonymous substitution in the activation loop of a receptor-like cytoplasmic kinase (RLCK), which we named MARIS (MRI). We show that MRI is a plasma membrane-localized member of the RLCK-VIII subfamily and is preferentially expressed in both PTs and root hairs. Interestingly, mri-knockout mutants display spontaneous PT and root-hair bursting. Moreover, expression of the MRIR240C mutant, but not its wild-type form, partially rescues the bursting phenotypes of anx1 anx2 PTs and fer root hairs but strongly inhibits wild-type tip growth. Thus, our findings identify a novel positive component of the CrRLK1L-dependent signaling cascade that coordinates CW integrity and tip growth.