The rust pathogens are one of the most complex fungi in the Basidiomycetes. The development of genomic resources for rust and other plant pathogens has opened the opportunities for functional genomics of fungal genes. Despite significant progress in the field of fungal genomics, functional characterization of the genome components has lacked, especially for the rust pathogens. Their obligate nature and lack of standard stable transformation protocol are the primary reasons for rusts to be one of the least explored genera despite its significance. In the recently sequenced rust genomes, a vast catalogue of predicted effectors and pathogenicity genes have been reported. However, most of these candidate genes remained unexplored due to the lack of suitable characterization methods. The heterologous expression of putative effectors in Nicotiana benthamiana and Arabidopsis thaliana has proved to be a rapid screening method for identifying the role of these effectors in virulence. However, no fungal system has been used for the functional validation of these candidate genes. The smuts, from the evolutionary point of view, are closely related to the rust pathogens. Moreover, they have been widely studied and hence could be a suitable model system for expressing rust fungal genes heterologously. The genetic manipulation methods for smuts are also well standardized. Complementation assays can be used for functional validation of the homologous genes present in rust and smut fungal pathogens, while the species-specific proteins can be expressed in the mutant strains of smut pathogens having reduced or no virulence for virulence analysis. We propose that smuts, especially Ustilago maydis, may prove to be a good model system to characterize rust effector proteins in the absence of methods to manipulate the rust genomes directly.

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黑穗病真菌作为表征锈病效应物的策略：机遇和挑战

锈病病原体是担子菌纲中最复杂的真菌之一。锈病和其他植物病原体基因组资源的开发为真菌基因的功能基因组学开辟了机会。尽管在真菌基因组学领域取得了重大进展，但缺乏对基因组成分的功能表征，尤其是对于锈病病原体。它们的专性性质和缺乏标准的稳定转化协议是锈菌成为研究最少的属之一的主要原因，尽管它很重要。在最近测序的锈病基因组中，已经报道了大量预测的效应子和致病基因。然而，由于缺乏合适的表征方法，这些候选基因中的大多数仍未被探索。在本氏烟草和拟南芥中推定效应子的异源表达已被证明是一种快速筛选方法，用于鉴定这些效应子在毒力中的作用。然而，没有真菌系统被用于这些候选基因的功能验证。从进化的角度来看，黑穗病与锈病病原体密切相关。此外，它们已被广泛研究，因此可以成为异源表达锈菌基因的合适模型系统。黑穗病的遗传操作方法也得到了很好的标准化。互补分析可用于对锈病和黑穗病真菌病原体中存在的同源基因进行功能验证，而种特异性蛋白可以在毒力降低或无毒力的黑穗病病原体突变株中表达，用于毒力分析。我们建议黑穗病，尤其是黑粉病，可能被证明是一种很好的模型系统，可以在没有直接操纵锈病基因组的方法的情况下表征锈病效应蛋白。