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Arabidopsis response regulators in cytokinin signaling and development.

机译：细胞激肽信号传导和发育中的拟南芥响应调节剂。

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摘要

The plant hormone cytokinin is involved in many processes in the plant, including cell division, seed germination, photomorphogenesis, shoot and root development, leaf senescence and seed set. The model for cytokinin signaling is similar to a two-component phosphorelay with which bacteria sense and respond to environmental stimuli. The cytokinin receptors are Hybrid Histidine Kinases that autophosphorylate on a conserved histidine residue in response to cytokinin binding. The phosphoryl group is transferred via an intermediate Histidine Phosphotransfer Protein to a conserved aspartate residue on the receiver domain of a Response Regulator.;Members of the Response Regulator protein family in Arabidopsis thaliana (ARRs) contain the conserved N-terminal receiver domain required for phosphorylation by two-component elements and can be classified into three groups based on sequence similarity and protein structure: type-A, type-B and type-C ARRs. The ten type-A ARRs are rapidly up-regulated by cytokinin treatment but their sequences do not predict known outputs. The eleven type-B ARRs have DNA binding and transactivating activity and are positive activators of cytokinin-regulated transcription. The pair of type-C ARRs are less similar in sequence to the two other groups of ARRs, are not transcriptionally regulated by cytokinin and do not have transcriptional activity.;In order to study the role of type-A ARR in cytokinin signaling and development, I have isolated multiple type-A arr loss-of function mutants up to a septuple arr3,4,5,6,7,8,9 mutant. Type-A arr mutants exhibit additive hypersensitivity to cytokinin, indicating that type-A ARRs play overlapping roles in negatively regulating cytokinin response. Subsets of type-A arr mutants show specific responses consistent with their patterns of expression. In particular, a subset of type-A ARRs interact with the meristem maintenance gene WUSCHEL to modulate shoot meristem activity. To further investigate the role of phosphorelay on type-A ARR function, I constructed site-directed mutants targeting the conserved aspartate phosphorylation site and tested their functions in planta. My results indicate that type-A ARR proteins are activated by phosphorylation and are likely to function by phospho-dependent interactions, with implications for functional specification.
机译：植物激素细胞分裂素参与植物的许多过程，包括细胞分裂，种子发芽，光形态发生，枝和根发育，叶片衰老和种子结实。细胞分裂素信号传导的模型类似于细菌感知和响应环境刺激的两组分磷酸化。细胞分裂素受体是杂交组氨酸激酶，其响应于细胞分裂素结合而在保守的组氨酸残基上自磷酸化。磷酸基团通过中间的组氨酸磷酸转移蛋白转移至应答调节剂受体结构域上的保守天冬氨酸残基。拟南芥（ARR）应答调节蛋白家族的成员包含磷酸化所需的保守的N端受体结构域由两成分组成，根据序列相似性和蛋白质结构可分为三类：A型，B型和C型ARR。十种A型ARR通过细胞分裂素处理迅速上调，但它们的序列无法预测已知的输出。十一个B型ARR具有DNA结合和反式激活活性，并且是细胞分裂素调节转录的阳性激活剂。这对C型ARR与其他两组ARR在序列上不太相似，不受细胞分裂素的转录调控，并且不具有转录活性。；为了研究A型ARR在细胞分裂素信号传导和发育中的作用，我已分离出多个A型arr丧失功能的突变体，直至一个个arr3,4,5,6,7,8,9突变体。 A型arr突变体表现出对细胞分裂素的加性超敏反应，表明A型ARR在负调节细胞分裂素反应中起重叠作用。 A型arr突变体的子集显示出与其表达模式一致的特异性反应。特别是，A型ARR的子集与分生组织维持基因WUSCHEL相互作用，以调节芽分生组织的活性。为了进一步研究磷光体在A型ARR功能上的作用，我构建了针对保守的天冬氨酸磷酸化位点的定点突变体，并在植物中测试了它们的功能。我的结果表明，A型ARR蛋白通过磷酸化被激活，并可能通过依赖磷酸的相互作用而起作用，这对功能规格具有影响。

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  • 作者

    To, Jennifer PokChun.;

  • 作者单位

    The University of North Carolina at Chapel Hill.;

  • 授予单位 The University of North Carolina at Chapel Hill.;
  • 学科 Biology Molecular.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 191 p.
  • 总页数 191
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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