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False smut of rice, caused by Ustilaginoidea virens, has become one of the most important diseases in rice-growing regions worldwide. The disease causes a significant yield loss and imposes health threats to humans and animals by producing mycotoxins. In this review, we update our understanding of the pathogen, including the disease cycle and infection strategies, the decoding of the U. virens genome, comparative/functional genomics, and effector biology. Whereas the decoding of the U. virens genome unveils specific adaptations of the pathogen in successfully occupying rice flowers, progresses in comparative/functional genomics and effector biology have begun to uncover the molecular mechanisms underlying U. virens virulence and pathogenicity. We highlight the identification and characterization of the produced mycotoxins and their biosynthetic pathways in U. virens.The management strategies for this disease are also discussed. The flower-specific infection strategy makes the pathogen a unique tool to unveil novel mechanisms for the interactions between nonobligate biotrophic pathogens and their hosts. [ABSTRACT FROM AUTHOR]

Rice false smut, caused by Ustilaginoidea virens, is one of the most important diseases in rice. The disease not only causes significant yield losses in China and worldwide but also produces multiple types of mycotoxins that pose a serious threat to the health of humans and animals. To effectively prevent and control the disease, the pathogenicity mechanisms of U. virens have been studied preliminarily, and some control strategies have been developed. This review focuses on recent progress in understanding the molecular mechanisms of U. virens pathogenicity, including virulence-related genes, transcriptional regulation of virulence genes, and effector-mediated interactions between rice and U. virens. Based on the molecular mechanisms underlying the rice-U. virens interactions, the possibilities of the pathogenicity genes in U. virens and host immune-related genes as potential targets for biological agents, host-induced gene silencing, and molecular design breeding are also discussed. [ABSTRACT FROM AUTHOR]

Ustilaginoidea virens, which causes rice false smut (RFS), is one of the most detrimental rice fungal diseases and poses a severe threat to rice production and quality. Effectors in U. virens often act as a group of essential virulence factors that play crucial roles in the interaction between host and the pathogen. Thus, the functions of individual effectors in U. virens need to be further explored. Here, we demonstrated a small secreted hypersensitive response-inducing protein (hrip), named UvHrip1, which was highly conserved in U. virens isolates. UvHrip1 was also proven to suppress necrosis-like defense symptoms in N. benthamiana induced by the oomycete elicitor INF1. The localization of UvHrip1 was mainly in the nuclei and cytoplasm via monitoring the UvHrip1-GFP fusion protein in rice cells. Furthermore, Y2H and BiFC assay demonstrated that UvHrip1 interacted with OsHGW, which is a critical regulator in heading date and grain weight signaling pathways in rice. Expression patterns of defense- and heading date-related genes, OsPR1#051 and OsMYB21, were down-regulated over U. virens infection in rice. Collectively, our data provide a theory for gaining an insight into the molecular mechanisms underlying the UvHrip1 virulence function. [ABSTRACT FROM AUTHOR]