生物胁迫应答机制研究组

稻曲病菌的侵染及水稻基因的差异表达

稻曲病是水稻生产上的一种重要穗部病害,是由Ustilaginoidea virens 真菌引起的。U. virens 能侵染水稻的花器官,但U. virens 早期的侵染过程及水稻颖花的不同花器官在U. virens侵染过程中的作用还不清楚。我们通过农杆菌介导的遗传转化法,将标记基因GFP转到U. virens 菌株中,通过GFP来观察U. virens真菌的侵染过程。另外,为了研究在U. virens侵染过程中水稻基因的表达情况,利用RNA-Seq技术,比较了U. virens侵染水稻颖花前后基因的表达水平,结果表明,许多与植物激素相关的基因在U. virens侵染前后的表达水平上存在显著差异,其中最显著的是与油菜素内酯信号传导相关的基因,这可能暗示油菜素内酯在U. virens的侵染过程中起重要作用。

Characterization of Ustilaginoidea virens infection in rice

Rice false smut, caused by the fungus Ustilaginoidea virens, is one of the most destructive diseases of rice (Oryza sativa L.) production. As a flower-infecting fungus, how U. virens infects rice in natural conditions remains unclear. We monitored the early processes of fungal infection using in vitro co-cultivation of U. virens strain with young rice panicles on half MS medium. At day 5 after infection, hyphae emerged and enclosed rice spikelets. We observed that hyphae entered florets through the aperture of the apex of glumes, firstly occupied the upper space of the flower organs and formed a three-dimensional network, then grew downward to invade the stamens and pistil. We used freshly collected smut balls to observe the processes of U. virens infection and found that U. virens decomposes the contents of the cells, especially, it digests the integuments of ovary. This may be the critical strategy for U. virens to propagate in the infected rice spikelets. We did not observe fungal hyphae in the vascular bundles of pedicel, implicating that U. virens is not a systemic flower-infecting fungus.
To further explore the molecular processes of the interaction between U. virens and rice plants, we performed RNA sequencing (RNA-Seq) to compare differential expression of genes in resistant/susceptible rice in responding to U. virens infection. For phytohormones, the largest number of genes involved in brassinosteroids signaling were found to be differentially modulated in resistant and susceptible rice during the processed of U. virens infection, implicating that brassinosteroids may play more important roles than the other hormones in response to U. virens infection.



图1 GFP-标记的U. Virens侵染水稻颖花(箭头)

图2 U. virens 侵染引起基因在水稻抗性/感病品种中

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