拟南芥类受体激酶BAK1和BKK1介导的细胞死亡的分子机理研究

发布时间：2018-06-03 10:21

本文选题：拟南芥 + 类受体激酶　；参考：《兰州大学》2017年博士论文

【摘要】：拟南芥类受体激酶BAK1和BKK1参与多种生理过程,其中包括油菜素内酯信号途径和PRR介导的PTI途径。我们先前的研究发现bak1 bkk1双突变体在正常的生长条件下能够自发的产生细胞死亡表型,而且这种细胞死亡表型的发生是依赖于光的。尽管我们已知BAK1和BKK1介导的细胞死亡可能与水杨酸有关,但其背后的分子机理和细胞死亡途径中的组分我们仍然未知。本论文中我们将光如何诱发细胞死亡作为切入点进行了深入、系统的研究,并且鉴定到ETI组分在细胞死亡信号通路中具有重要的作用。我们发现光能够诱发细胞死亡,但在黑暗条件下外源施加水杨酸同样可以重现出细胞死亡,说明光诱导的水杨酸积累才是细胞死亡发生的真正诱因。水杨酸合成和转运相关基因SID2和EDS5在bak1-4bkk1-1体内高度表达。当二者缺失突变体分别与bak1-3 bkk1-1杂交后能够有效抑制细胞死亡表型的发生。除此之外,编码叶绿体重要组分基因THF1缺失突变也可抑制bak1-3 bkk1-1的细胞死亡,说明光诱导叶绿体形态建成后水杨酸的爆发是细胞死亡产生的重要因素。由于水杨酸在植物抗病方面具有重要作用,因此我们对以上水杨酸相关突变体进行了抗病性实验,结果显示单突变体bak1-3和bkk1-1相较于野生型对Pst DC3000具有更强的感病性,而双突变体bak1-3 bkk1-1却具有更强的抗病性。对flg22的响应实验证明bak1 bkk1体内激活的免疫途径是ETI而非PTI。而进一步的遗传学数据表明,ETI途径重要组分RBB3、EDS1和PAD4参与该细胞死亡途径。在以上内容中我们首次揭示了BAK1和BKK1介导的细胞死亡的发生原因,该途径细胞死亡的发生是光诱发的水杨酸积累和ETI途径共同促成的结果。除此之外,本论文中我们详细的论述了bak1 bkk1的遗传抑制子sbb1(编码一个核孔蛋白)在该细胞死亡途径中的功能。遗传学实验证明SBB1缺失突变能够明显抑制bak1 3 bkk1 1的细胞死亡症状。此外,与SBB1同属一个亚复合物的其它三个成员基因和一个DEAD-box RNA解旋酶基因DRH1缺失突变后同样可以极大程度的挽救细胞死亡表型。进一步研究发现这些突变体中的mRNA在细胞核中会发生明显的积累,表明mRNA在细胞核质间的分布对细胞死亡的发生具有重要的作用。综上所述,本论文共得出如下结论:光诱导叶绿体形态建成后的水杨酸积累促发了BAK1和BKK1介导的细胞死亡的发生;ETI途径参与BAK1和BKK1介导的细胞死亡;NUP107-160部分成员和RNA解旋酶DRH1在BAK1和BKK1介导的细胞死亡中具有重要的作用,其突变体可能是通过影响某些水杨酸或ETI相关的转录本在核质间的分布来抑制细胞死亡发生的。
[Abstract]:Arabidopsis receptor kinase BAK1 and BKK1 are involved in a variety of physiological processes, including the Brassinolide signaling pathway and the PRR mediated PTI pathway. Our previous studies have found that bak1 bkk1 double mutants can spontaneously produce cell death phenotypes under normal growth conditions, and the occurrence of these cell death phenotypes depends on light. Although we know that BAK1 and BKK1 mediated cell death may be related to salicylic acid, the underlying molecular mechanism and the components of cell death pathway are unknown. In this thesis, we have made a deep and systematic study on how light induces cell death, and we have identified that the ETI component plays an important role in the cell death signaling pathway. We found that light can induce cell death, but exogenous salicylic acid can reproduce cell death under dark conditions, indicating that the accumulation of salicylic acid induced by light is the real inducement of cell death. Salicylic acid biosynthesis and transportation-related genes SID2 and EDS5 are highly expressed in bak1-4bkk1-1. When the two deletion mutants were hybridized with bak1-3 bkk1-1, they could effectively inhibit the occurrence of cell death phenotype. In addition, the deletion mutation of THF1 encoding an important chloroplast component gene can also inhibit the cell death of bak1-3 bkk1-1, indicating that the outbreak of salicylic acid after photoinduced chloroplast morphogenesis is an important factor in the production of cell death. Because salicylic acid plays an important role in plant disease resistance, we have tested the above salicylic acid-related mutants for disease resistance. The results show that single mutant bak1-3 and bkk1-1 are more susceptible to Pst DC3000 than wild type. The double mutant bak1-3 bkk1-1 has stronger resistance to disease. The response to flg22 showed that the immune pathway of bak1 bkk1 in vivo was ETI, not PTI. Further genetic data suggested that RBB3 EDS1 and PAD4, an important component of the ETI pathway, were involved in the cell death pathway. The causes of cell death mediated by BAK1 and BKK1 were revealed for the first time. The cell death in this pathway was caused by the accumulation of salicylic acid induced by light and the ETI pathway. In addition, the function of bak1 bkk1 genetic suppressor sbb1 (encoding a nucleoporous protein) in the cell death pathway is discussed in detail. Genetic experiments showed that SBB1 deletion mutation could significantly inhibit the cell death symptoms of bak1 3 bkk1 1. In addition, the other three genes that belong to the same subcomplex as SBB1 and one DEAD-box RNA helicase gene DRH1 deletion mutation can also greatly save the cell death phenotype. Further studies showed that the mRNA in these mutants accumulated significantly in the nucleus, indicating that the distribution of mRNA in the cytoplasm played an important role in the occurrence of cell death. In summary, In this thesis, we conclude that the accumulation of salicylic acid after chloroplast morphogenesis promotes the development of cell death mediated by BAK1 and BKK1. The ETI pathway is involved in the BAK1 and BKK1 mediated cell death (Nup107-160) members and RNA helicase DRH1. It plays an important role in cell death mediated by BAK1 and BKK1. Its mutants may inhibit cell death by affecting the distribution of some salicylic acid or ETI related transcripts between nuclei and cytoplasm.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：Q943.2

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