Molecular Plant Pathology, University of Amsterdam, Amsterdam, Netherlands.
Genetwister Technologies B.V., Wageningen, Netherlands.
Mol Plant Pathol. 2020 Jun;21(6):761-776. doi: 10.1111/mpp.12927. Epub 2020 Apr 4.
Fusarium oxysporum f. sp. radicis-cucumerinum (Forc) causes severe root rot and wilt in several cucurbit species, including cucumber, melon, and watermelon. Previously, a pathogenicity chromosome, chr , was identified in Forc. Strains that were previously nonpathogenic could infect multiple cucurbit species after obtaining this chromosome via horizontal chromosome transfer (HCT). In contrast, F. oxysporum f. sp. melonis (Fom) can only cause disease on melon plants, even though Fom contains contigs that are largely syntenic with chr . The aim of this study was to identify the genetic basis underlying the difference in host range between Fom and Forc. First, colonization of different cucurbit species between Forc and Fom strains showed that although Fom did not reach the upper part of cucumber or watermelon plants, it did enter the root xylem. Second, to select candidate genomic regions associated with differences in host range, high-quality genome assemblies of Fom001, Fom005, and Forc016 were compared. One of the Fom contigs that is largely syntenic and highly similar in sequence to chr contains the effector gene SIX6. After HCT of the SIX6-containing chromosome from Fom strains to a nonpathogenic strain, the recipient (HCT) strains caused disease on melon plants, but not on cucumber or watermelon plants. These results provide strong evidence that the differences in host range between Fom and Forc are caused by differences between transferred chromosomes of Fom and chr , thus narrowing down the search for genes allowing or preventing infection of cucumber and watermelon to genes located on these chromosomes.
尖镰孢古巴专化型（Forc）引起多种葫芦科植物（包括黄瓜、甜瓜和西瓜）的严重根腐和萎蔫。先前，在 Forc 中鉴定出一个致病性染色体 chr。通过水平染色体转移（HCT）获得该染色体后，先前非致病性的菌株可以感染多种葫芦科物种。相比之下，尖镰孢古巴专化型（Fom）只能引起甜瓜植物发病，尽管 Fom 含有与 chr 大部分同源的 contigs。本研究旨在鉴定 Fom 和 Forc 之间宿主范围差异的遗传基础。首先，比较了 Forc 和 Fom 菌株对不同葫芦科物种的定植，结果表明尽管 Fom 不能到达黄瓜或西瓜植株的上部，但它确实进入了根部木质部。其次，为了选择与宿主范围差异相关的候选基因组区域，对 Fom001、Fom005 和 Forc016 的高质量基因组组装进行了比较。一个与 chr 高度同源且大部分同源的 Fom contig 包含效应基因 SIX6。将 Fom 菌株中包含 SIX6 的染色体 HCT 到非致病性菌株后，受体（HCT）菌株会引起甜瓜植物发病，但不会引起黄瓜或西瓜植物发病。这些结果有力地证明了 Fom 和 Forc 之间宿主范围的差异是由 Fom 和 chr 的转移染色体之间的差异引起的，从而缩小了寻找允许或阻止黄瓜和西瓜感染的基因的范围，将搜索范围缩小到这些染色体上的基因。
