Plant pathogen effectors play important roles in parasitism, including countering plant immunity. However, investigations of the emergence and diversification of fungal effectors across host-adapted populations has been limited. We previously identified a gene encoding a suppressor of plant cell death in Pyricularia oryzae (syn. Magnaporthe oryzae). Here, we report the gene is one of a 21-member gene family and we characterize sequence diversity in different populations. Within the rice pathogen population, nucleotide diversity is low, however; the majority of gene family members display presence-absence polymorphism or other null alleles. Gene family allelic diversity is greater between host-adapted populations and, thus, we named them host-adapted genes (HAGs). Multiple copies of HAGs were found in some genome assemblies and sequence divergence between the alleles in two cases suggested they were the result of repeat-induced point mutagenesis. Transfer of family members between populations and novel HAG haplotypes resulting from apparent recombination were observed. HAG family transcripts were induced in planta and a subset of HAGs are dependent on a key regulator of pathogenesis, PMK1. We also found differential intron splicing for some HAGs that would prevent ex planta protein expression. For some genes, spliced transcript was expressed in antiphase with an overlapping antisense transcript. Characterization of HAG expression patterns and allelic diversity reveal novel mechanisms for HAG regulation and mechanisms generating sequence diversity and novel allele combinations. This evidence of strong in planta–specific expression and selection operating on the HAG family is suggestive of a role in parasitism.

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植物病原体效应物在寄生中起着重要作用，包括抵抗植物免疫力。然而，在适应宿主的人群中真菌效应子的出现和多样化的研究是有限的。我们先前确定编码在植物细胞死亡的抑制基因稻瘟病菌（同义词稻瘟病菌）。在这里，我们报告该基因是21个成员的基因家族之一，并描述了不同人群中的序列多样性。然而，在水稻病原体种群中，核苷酸多样性很低。大多数基因家族成员表现出不存在的多态性或其他无效等位基因。基因家族等位基因多样性在适应宿主的种群之间更大，因此，我们将它们命名为适应宿主的基因（HAGs）。在某些基因组组装中发现了多个HAG拷贝，并且在两种情况下等位基因之间的序列差异表明它们是重复诱导点诱变的结果。观察到族群在种群之间的转移以及由于表观重组而产生的新的HAG单倍型。HAG家族转录物在植物中被诱导，并且一部分HAG依赖于发病机理的关键调节因子PMK1。我们还发现某些HAG的差异内含子剪接会阻止植物原蛋白的表达。对于某些基因，剪接的转录物在反相中以重叠的反义转录物表达。HAG的表征表达模式和等位基因多样性揭示了HAG调节的新机制以及产生序列多样性和新等位基因组合的机制。这种在HAG家族中有效的植物特异性表达和选择的强烈证据表明在寄生虫中起作用。

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