Department of Disease and Stress Biology, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK.
Mol Plant Pathol. 2005 Sep 1;6(5):551-9. doi: 10.1111/j.1364-3703.2005.00302.x.
SUMMARY Avirulence (avr) determinants are incompatibility factors which elicit host plant defence responses in a gene-for-gene manner. They are produced by fungi, bacteria and viruses, and their recognition by resistance genes has been extensively studied for decades. But why should a microbe keep a molecule that allows it to be recognized? One argument is that avr genes perform some essential function and must be kept despite giving the pathogen away. Many bacterial avr determinants have been shown to be effectors, which contribute to virulence and aggressiveness. If this were always the case, mutants lacking these essential molecules would be at a serious disadvantage. Some disadvantage has been shown for a small number, but for the majority there is no effect on virulence. This has been explained by functional redundancy for bacterial and fungal avr determinants, with other molecules compensating for the deletion of these essential genes. However, this argument is counter-intuitive because by definition these individual genes are no longer essential; so why keep them? With increasing numbers of avr genes being identified, efforts to elucidate their function are increasing. In this review, we take stock of the accumulating literature, and consider what the real function of avr determinants might be.
摘要 无毒（avr）决定因素是不相容因子，以基因对基因的方式引发宿主植物防御反应。它们由真菌、细菌和病毒产生，其抗性基因的识别已被广泛研究了几十年。但是，微生物为什么要保留一种可以被识别的分子呢？有一种观点认为，avr 基因具有某些必需的功能，尽管它会使病原体被识别出来，但仍必须保留。许多细菌 avr 决定因素已被证明是效应子，它们有助于毒力和侵袭性。如果情况总是如此，缺乏这些必需分子的突变体将处于严重劣势。已经证明少数情况下会有一些劣势，但对于大多数情况，这些分子的缺失对毒力没有影响。这可以用细菌和真菌 avr 决定因素的功能冗余来解释，其他分子可以补偿这些必需基因的缺失。然而，这种观点是违反直觉的，因为根据定义，这些单个基因不再是必需的；那么为什么要保留它们呢？随着越来越多的 avr 基因被鉴定出来，人们越来越努力阐明它们的功能。在这篇综述中，我们对不断积累的文献进行了总结，并考虑了 avr 决定因素的真正功能可能是什么。
