Department of Plant Cytology and Embryology, Institute of Botany, Faculty of Biology, Jagiellonian University in Kraków, 9 Gronostajowa Str., 30-387 Kraków, Poland.
Cells. 2021 Jan 4;10(1):65. doi: 10.3390/cells10010065.
Programmed cell death (PCD) is a process that plays a fundamental role in plant development and responses to biotic and abiotic stresses. Knowledge of plant PCD mechanisms is still very scarce and is incomparable to the large number of studies on PCD mechanisms in animals. Quick and accurate assays, e.g., the TUNEL assay, comet assay, and analysis of caspase-like enzyme activity, enable the differentiation of PCD from necrosis. Two main types of plant PCD, developmental (dPCD) regulated by internal factors, and environmental (ePCD) induced by external stimuli, are distinguished based on the differences in the expression of the conserved PCD-inducing genes. Abiotic stress factors, including heavy metals, induce necrosis or ePCD. Heavy metals induce PCD by triggering oxidative stress via reactive oxygen species (ROS) overproduction. ROS that are mainly produced by mitochondria modulate phytotoxicity mechanisms induced by heavy metals. Complex crosstalk between ROS, hormones (ethylene), nitric oxide (NO), and calcium ions evokes PCD, with proteases with caspase-like activity executing PCD in plant cells exposed to heavy metals. This pathway leads to very similar cytological hallmarks of heavy metal induced PCD to PCD induced by other abiotic factors. The forms, hallmarks, mechanisms, and genetic regulation of plant ePCD induced by abiotic stress are reviewed here in detail, with an emphasis on plant cell culture as a suitable model for PCD studies. The similarities and differences between plant and animal PCD are also discussed.
程序性细胞死亡（PCD）是一个在植物发育和对生物及非生物胁迫的响应中起基本作用的过程。尽管人们对植物 PCD 机制的了解还非常有限，但与动物 PCD 机制的大量研究相比，这仍然是微不足道的。快速准确的检测方法，例如 TUNEL 检测、彗星检测和半胱天冬酶样酶活性分析，能够区分 PCD 与坏死。基于保守的 PCD 诱导基因的表达差异，将植物 PCD 分为两种主要类型，即由内部因素调控的发育型（dPCD）和由外部刺激诱导的环境型（ePCD）。非生物胁迫因素，包括重金属，通过过度产生活性氧物种（ROS）来诱导坏死或 ePCD。ROS 主要由线粒体产生，调节重金属诱导的植物毒性机制。ROS、激素（乙烯）、一氧化氮（NO）和钙离子之间的复杂串扰引发 PCD，重金属暴露的植物细胞中的具有半胱天冬酶样活性的蛋白酶执行 PCD。这条途径导致重金属诱导的 PCD 与其他非生物因素诱导的 PCD 具有非常相似的细胞学特征。本文详细综述了非生物胁迫诱导的植物 ePCD 的形式、特征、机制和遗传调控，重点介绍了植物细胞培养作为 PCD 研究的合适模型。还讨论了植物和动物 PCD 之间的相似性和差异。
