National Agri-Food Biotechnology Institute (NABI), Sector-81 (Knowledge City), PO Manauli, S.A.S. Nagar, Mohali, Punjab, 140306, India.
ICAR-National Institute for Plant Biotechnology, Pusa Campus, New Delhi, 110012, India.
World J Microbiol Biotechnol. 2020 Sep 14;36(10):150. doi: 10.1007/s11274-020-02927-x.
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.
锈菌病原体是担子菌中最复杂的真菌之一。锈菌和其他植物病原体基因组资源的发展为真菌基因的功能基因组学开辟了机会。尽管真菌基因组学领域取得了重大进展，但对基因组成分的功能表征仍缺乏研究，尤其是对于锈菌病原体。由于其专性和缺乏标准的稳定转化方案，锈菌是研究最少的属之一。在最近测序的锈菌基因组中，已经报道了大量预测的效应物和致病性基因。然而，由于缺乏合适的表征方法，大多数候选基因仍未得到探索。在拟南芥和烟草中异源表达假定的效应物已被证明是鉴定这些效应物在毒力中作用的快速筛选方法。然而，尚未在真菌系统中用于这些候选基因的功能验证。从进化的角度来看，黑粉菌与锈菌病原体密切相关。此外，它们已经得到了广泛的研究，因此可以作为表达锈菌真菌基因的合适模型系统。黑粉菌的遗传操作方法也已经标准化。互补测定可用于验证锈菌和黑粉菌病原体中同源基因的功能，而物种特异性蛋白可在具有降低或无毒性的黑粉菌病原体突变株中表达，用于毒性分析。我们提出，黑粉菌，特别是玉米黑粉菌，可能在没有直接操纵锈菌基因组的方法的情况下，成为表征锈菌效应蛋白的良好模型系统。
