Effect of temperature on the development of sclerotia in Villosiclava virens

The sclerotia of Villosiclava virens were found commonly in high altitude and the temperate regions, where the temperatures are relatively low in rice filling stage. To make sure if low temperature induce the sclerotial formation in V. virens, the inoculated rice panicles in laboratory and the diseased rice panicles cut from paddy fields were treated under different temperatures. The results showed that 3 days of night temperature at 15°C were enough to induce the sclerotial formation. The low temperature was much more effective for young balls with intact membranes. After appearance of chlamydospores on the ball surfaces, the sclerotium could not differentiate anymore. The sclerotia began to differentiate below the chlamydospore layer and gradually grew onto the ball surfaces. This suggests that low temperature in the early development stage of false smut balls is an important factor to induce the sclerotial differentiation, and rice cultivars with long growth periods are able to produce more sclerotium-bearing balls, which will produce mass of spores in paddy field in the coming year.

The Wolfiporia cocos Genome and Transcriptome Shed Light on the Formation of Its Edible and Medicinal Sclerotium

Wolfiporia cocos(F. A. Wolf) has been praised as a food delicacy and medicine for centuries in China. Here, we present the genome and transcriptome of the Chinese strain CGMCC5.78 of W. cocos. High-confidence functional prediction was made for 9277 genes among the 10,908 total predicted gene models in the W. cocos genome. Up to 2838 differentially expressed genes(DEGs)were identified to be related to sclerotial development by comparing the transcriptomes of mycelial and sclerotial tissues. These DEGs are involved in mating processes, differentiation of fruiting body tissues, and metabolic pathways. A number of genes encoding enzymes and regulatory factors related to polysaccharide and triterpenoid production were strikingly regulated. A potential triterpenoid gene cluster including the signature lanosterol synthase(LSS) gene and its modified components were annotated. In addition, five nonribosomal peptide synthase(NRPS)-like gene clusters,eight polyketide synthase(PKS) gene clusters, and 15 terpene gene clusters were discovered in the genome. The differential expression of the velevt family proteins, transcription factors,carbohydrate-active enzymes, and signaling components indicated their essential roles in the regulation of fungal development and secondary metabolism in W. cocos. These genomic and transcriptomic resources will be valuable for further investigations of the molecular mechanisms controlling sclerotial formation and for its improved medicinal applications.