Department of Soil, Water and Environmental Science, University of Arizona, Fourth Street, Tucson, AZ 85721, USA.
Plant Sci. 2011 Jun;180(6):741-5. doi: 10.1016/j.plantsci.2011.02.007. Epub 2011 Mar 5.
This review discusses how extracellular DNA (exDNA) might function in plant defense, and at what level(s) of innate immunity this process might operate. A new role for extracellular factors in mammalian defense has been described in a series of studies. These studies reveal that cells including neutrophils, eosinophils, and mast cells produce 'extracellular traps' (ETs) consisting of histone-linked exDNA. When pathogens are attracted to such ETs, they are trapped and killed. When the exDNA component of ETs is degraded, trapping is impaired and resistance against invasion is reduced. Conversely, mutation of microbial genes encoding exDNases that degrade exDNA results in loss of virulence. This discovery that exDNases are virulence factors opens new avenues for disease control. In plants, exDNA is required for defense of the root tip. Innate immunity-related proteins are among a group of >100 proteins secreted from the root cap and root border cell populations. Direct tests revealed that exDNA also is rapidly synthesized and exported from the root tip. When this exDNA is degraded by the endonuclease DNase 1, root tip resistance to fungal infection is lost; when the polymeric structure is degraded more slowly, by the exonuclease BAL31, loss of resistance to fungal infection is delayed accordingly. The results suggest that root border cells may function in a manner analogous to that which occurs in mammalian cells.
这篇综述讨论了细胞外 DNA（exDNA）在植物防御中的作用，以及这一过程可能在先天免疫的哪个（些）水平上发挥作用。在一系列研究中，人们在哺乳动物防御中发现了细胞外因子的新作用。这些研究揭示了包括中性粒细胞、嗜酸性粒细胞和肥大细胞在内的细胞会产生由组蛋白连接的 exDNA 组成的“细胞外陷阱（ETs）”。当病原体被吸引到这些 ETs 时，它们会被捕获并杀死。当 ETs 的 exDNA 成分被降解时，捕获就会受到损害，入侵的抵抗力就会降低。相反，微生物基因编码的 exDNases（降解 exDNA 的酶）发生突变会导致毒力丧失。这一发现 exDNases 是毒力因子，为疾病控制开辟了新途径。在植物中，exDNA 是根尖防御所必需的。先天免疫相关蛋白是从根冠和根缘细胞群中分泌的 100 多种蛋白质之一。直接测试显示，exDNA 也会从根尖迅速合成并输出。当这种 exDNA 被内切核酸酶 DNase 1 降解时，根尖对真菌感染的抵抗力就会丧失；当多聚体结构被外切核酸酶 BAL31 更缓慢地降解时，根尖对真菌感染的抵抗力丧失也会相应延迟。结果表明，根缘细胞可能以类似于发生在哺乳动物细胞中的方式发挥作用。
