MAT1-1-3, a Mating Type Gene in the Villosiclava virens, Is Required for Fruiting Bodies and Sclerotia Formation, Asexual Development and Pathogenicity

Abstract

Villosiclava virens is the prevalent causative pathogen of rice false smut, a destructive rice disease. Mating-type genes play a vital role in the evolution of mating systems in fungi. Some fungi have lost MAT1-1-3 , one of the mating-type genes, during evolution, whereas others still retain MAT1-1-3 . However, how MAT1-1-3 regulates the sexual development of heterothallic V. virens remains unknown. Here, we generated the MAT1-1-3 mutants, which exhibited defects in vegetative growth, stress response, pathogenicity, sclerotia formation and fruiting body maturation. An artificial outcrossing inoculation assay showed that the Δ mat1-1-3 mutant was unable to produce sclerotia. Unexpectedly, the Δ mat1-1-3 mutant could form immature fruiting bodies without mating on potato sucrose agar medium (PSA) compared with the wild-type strain, most likely by activating the truncated MAT1-2-1 transcription to regulate the sexual development. Moreover, RNA-seq data showed that knockout of MAT1-1-3 results in misregulation of a subset of genes involved in sexual development, MAPK signaling, cell wall integrity, autophagy, epigenetic modification, and transcriptional regulation. Collectively, this study reveals that MAT1-1-3 is required for asexual and sexual development, and pathogenicity of V. virens , thereby provides new insights into the function of mating-type genes in the fungi life cycle and infection process.

The cyclase-associated protein UvCap1 is required for mycelial growth and pathogenicity in the rice false smut fungus

“…In the assays for mycelial growth of U. virens strains, the mycelia of the wild-type strain P-1, the ΔUvcap1 (#11, #14) mutant and the complemented Uvcap1-c (#1) were ground with a tissue blender (Waring Commercial Blender 8011S, USA) and diluted with potato sucrose broth (PSB), then individually spread evenly on PSA medium plates, and cultured at 28°C. A mycelial block (5 mm in diameter) cut from the margin of 5-day-old colony was inoculated on the center of a PSA or TB3 medium plate at 28°C for 20 days with 5 replicates for each group (Yu et al 2019;Yong et al 2020). Colony diameters were measured using the cross-measurement method.…”

“…About 5-7 days before heading, 1-2 mL of hyphae and conidia suspensions were injected into the panicles of rice plants using sterilized syringes. Inoculated rice plants were cultured in a humid environment with a water spray system and the number of rice false smut balls per panicle were counted at 30 dpi (Hu et al 2014;Yong et al 2020). The expansion of infection hyphae inside the spikelets of the wild-type strain P-1, the ΔUvcap1 (#11) mutant and its complemented Uvcap1-c (#1) were observed at 10, 14 and 18 dpi.…”

“…A mycelial block (5 mm in diameter) cut from the margin of 5-dayold colony was inoculated on the center of a PSA medium plate or PSA supplemented with different concentrations of stress agents, including 0.5 M NaCl, 0.6 M sorbitol, 500 μg/mL CFW, 100 μg/mL Congo red, 0.05% SDS and 0.05% H 2 O 2 . The plates were incubated in 28°C for 20 days, with five replicates for each group (Yu et al 2019;Yong et al 2020). Colony diameters were measured using the cross-measurement method.…”

“…Colony diameters were measured using the cross-measurement method. Inhibition rates were calculated as described previously (Xie et al 2019;Yong et al 2020).…”

“…Rice spikelets were collected at 0, 1, 2, 3, 5, 7 and 14 dpi. RNA was extracted using an RNA extraction kit (BioTeKe, China) and cDNA reverse transcription was performed with the PrimeScript™ RT reagent Kit with gDNA Eraser (TaKaRa, Japan) as previously described (Yong et al 2020). qPCR was performed in an ABI Q6 Real-Time System with primers UvCAP1-qF/qR (Additional file 2: Table S1).…”