Climate Change Cluster, University of Technology Sydney, Faculty of Science Building 4, Level 6 Corner of Thomas and, Harris St, Ultimo NSW 2007, Sydney, Australia.
Dpto. de Bioquímica, Facultad de Química, Conjunto E. Universidad Nacional Autónoma de México (UNAM). Ciudad Universitaria, 04510, Ciudad de México, México.
Sci Rep. 2020 Jun 25;10(1):10360. doi: 10.1038/s41598-020-65186-8.
In plants, pathogen triggered programmed cell death (PCD) is frequently mediated by polar lipid molecules referred as long chain bases (LCBs) or ceramides. PCD interceded by LCBs is a well-organized process where several cell organelles play important roles. In fact, light-dependent reactions in the chloroplast have been proposed as major players during PCD, however, the functional aspects of the chloroplast during PCD are largely unknown. For this reason, we investigated events that lead to disassembly of the chloroplast during PCD mediated by LCBs. To do so, LCB elevation was induced with Pseudomonas syringae pv. tomato (a non-host pathogen) or Fumonisin B1 in Phaseolus vulgaris. Then, we performed biochemical tests to detect PCD triggering events (phytosphingosine rises, MPK activation and HO generation) followed by chloroplast structural and functional tests. Observations of the chloroplast, via optical phenotyping methods combined with microscopy, indicated that the loss of photosynthetic linear electron transport coincides with the organized ultrastructure disassembly. In addition, structural changes occurred in parallel with accumulation of HO inside the chloroplast. These features revealed the collapse of chloroplast integrity and function as a mechanism leading to the irreversible execution of the PCD promoted by LCBs.
在植物中，病原体触发的程序性细胞死亡（PCD）通常由被称为长链碱基（LCB）或神经酰胺的极性脂质分子介导。由 LCB 介导的 PCD 是一个组织良好的过程，其中几个细胞器发挥着重要作用。事实上，已经提出叶绿体中的光依赖性反应是 PCD 过程中的主要参与者，然而，PCD 期间叶绿体的功能方面在很大程度上是未知的。出于这个原因，我们研究了由 LCB 介导的 PCD 过程中导致叶绿体解体的事件。为此，用丁香假单胞菌 pv。番茄（非宿主病原体）或在菜豆中诱导 LCB 升高。然后，我们进行了生化测试以检测 PCD 触发事件（植物鞘氨醇升高、MPK 激活和 HO 生成），随后进行了叶绿体结构和功能测试。通过光学表型方法与显微镜结合观察叶绿体，表明光合作用线性电子传递的丧失与有组织的超微结构解体同时发生。此外，结构变化与叶绿体内部 HO 的积累平行发生。这些特征揭示了叶绿体完整性和功能的崩溃，作为导致由 LCB 促进的 PCD 不可逆执行的机制。
