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Transcriptome analysis of virulence-differentiated Fusarium oxysporum f. sp.cucumerinum during their colonization of cucumber

Xiaohong Lu: Institute of Plant Protection, Chinese Academy of Agricultural Sciences

<div><span><em>Fusarium oxysporum </em></span><span>f. sp. <em>cucumerinum </em>(<em>Foc</em>) causes cucumber wilt worldwide. Previously, we found that the virulence of <em>Foc </em>was significantly enhanced after 5</span> successive cycles of inoculation and re-isolation on a <em>Foc</em>-resistant cucumber cultivar. To understand its mechanism, a high coverage of RNA-Seq was obtained from cucumber roots at early (24 hours post inoculation, or hpi) and later (120 hpi) stages of infection by the original strain foc-3b and its virulence-increased variant Ra-4, and from vegetative cultures grown on agar plates. Analysis of differentially expressed genes (DEG) induced <span><em>in planta </em></span>showed that at both 24 and 120 hpi, the number of DEGs of Ra-4 was greater than that of foc-3b, but the numbers of repressed DEGs were similar between the two types of strain, indicating that more genes were highly and rapidly expressed in the highly virulent strain when colonizing the host. Among these DEGs, 190 up-regulated and 360 down-regulated genes were overlapped between foc-3b and Ra-4, suggesting their apparent involvement in infection. Meanwhile, 286 and 366 DEGs, up-regulated at early and later stages respectively, were unique to Ra-4. These unique DEGs with a high potential for contribution to virulence enhancement, were mainly associated with secondary metabolism and signaling pathways by analysis of their protein characteristics. This result provides a critical resource for studying rapid <span>adaption and evolution of<em> Foc</em></span> under host selection pressure.</div>