Walters Dale R, McRoberts Neil, Fitt Bruce D L
Crop & Soil Systems Research Group, Scottish Agricultural College, West Mains Road, Edinburgh EH9 3JG, UK.
Biol Rev Camb Philos Soc. 2008 Feb;83(1):79-102. doi: 10.1111/j.1469-185X.2007.00033.x. Epub 2007 Dec 17.
The term green island was first used to describe an area of living, green tissue surrounding a site of infection by an obligately biotrophic fungal pathogen, differentiated from neighbouring yellowing, senescent tissue. However, it has now been used to describe symptoms formed in response to necrotrophic fungal pathogens, virus infection and infestation by certain insects. In leaves infected by obligate biotrophs such as rust and powdery mildew pathogens, green islands are areas where senescence is retarded, photosynthetic activity is maintained and polyamines accumulate. We propose such areas, in which both host and pathogen cells are alive, be termed green bionissia. By contrast, we propose that green areas associated with leaf damage caused by toxins produced by necrotrophic fungal pathogens be termed green necronissia. A range of biotrophic/hemibiotrophic fungi and leaf-mining insects produce cytokinins and it has been suggested that this cytokinin secretion may be responsible for the green island formation. Indeed, localised cytokinin accumulation may be a common mechanism responsible for green island formation in interactions of plants with biotrophic fungi, viruses and insects. Models have been developed to study if green island formation is pathogen-mediated or host-mediated. They suggest that green bionissia on leaves infected by biotrophic fungal pathogens represent zones of host tissue, altered physiologically to allow the pathogen maximum access to nutrients early in the interaction, thus supporting early sporulation and increasing pathogen fitness. They lead to the suggestion that green islands are 'red herrings', representing no more than the consequence of the infection process and discrete changes in leaf senescence.
“绿岛”一词最初用于描述由专性活体营养型真菌病原体感染部位周围的一片有生命的绿色组织区域，与相邻的发黄、衰老组织不同。然而，现在它已被用于描述对坏死营养型真菌病原体、病毒感染以及某些昆虫侵害所形成的症状。在被锈菌和白粉病病原体等专性活体营养型病原体感染的叶片中，绿岛是衰老受到抑制、光合活性得以维持且多胺积累的区域。我们提议将宿主细胞和病原体细胞均存活的此类区域称为“绿色生物共生区”。相比之下，我们提议将与坏死营养型真菌病原体产生的毒素所导致的叶片损伤相关的绿色区域称为“绿色坏死共生区”。一系列活体营养型/半活体营养型真菌和潜叶昆虫会产生细胞分裂素，有人认为这种细胞分裂素的分泌可能是绿岛形成的原因。事实上，局部细胞分裂素积累可能是植物与活体营养型真菌、病毒和昆虫相互作用中绿岛形成的共同机制。已经开发出模型来研究绿岛形成是病原体介导的还是宿主介导的。这些模型表明，被活体营养型真菌病原体感染的叶片上的绿色生物共生区代表宿主组织区域，其生理状态发生改变，以便在相互作用早期让病原体最大限度地获取养分，从而支持早期孢子形成并提高病原体的适合度。这进而引发一种观点，即绿岛是“干扰因素”，只不过是感染过程和叶片衰老离散变化的结果。
