A circular single-stranded DNA mycovirus infects plants and confers broad-spectrum fungal resistance

Circular single-stranded DNA(ssDNA)viruses have been rarely found in fungi,and the evolutionary and ecological relationships among ssDNA viruses infecting fungi and other organisms remain unclear.In this study,a novel circular ssDNA virus,tentatively named Diaporthe sojae circular DNA virus 1(DsCDV1),was identified in the phytopathogenic fungus Diaporthe sojae isolated from pear trees.DsCDV1 has a monopartite genome(3185 nt in size)encapsidated in isometric virions(21-26 nm in diameter).The genome comprises seven putative open reading frames encoding a discrete replicase(Rep)split by an intergenic region,a putative capsid protein(CP),several proteins of unknown function(P1-P4),and a long intergenic region.Notably,the two split parts of DsCDV1 Rep share high identities with the Reps of Geminiviridae and Genomoviridae,respectively,indicating an evolutionary linkage with both families.Phylogenetic analysis based on Rep or CP sequences placed DsCDV1 in a unique cluster,supporting the establishment of a new family,tentatively named Gegemycoviridae,intermediate to both families.DsCDV1 significantly attenuates fungal growth and nearly erases fungal virulence when transfected into the host fungus.Remarkably,DsCDV1 can systematically infect tobacco and pear seedlings,providing broad-spectrum resistance to fungal diseases.Subcellular localization analysis revealed that DsCDV1 P3 is systematically localized in the plasmodesmata,while its expression in trans-complementation experiments could restore systematic infection of a movement-deficient plant virus,suggesting that P3 is a movement protein.DsCDV1 exhibits unique molecular and biological traits not observed in other ssDNA viruses,serving as a link between fungal and plant ssDNA viruses and presenting an evolutionary connection between ssDNA viruses and fungi.These findings contribute to expanding our understanding of ssDNA virus diversity and evolution,offering potential biocontrol applications for managing crucial plant diseases.

日本结缕草叶斑病病原鉴定及其生物学特性研究

从日本结缕草Zoysia japonica发病叶片上分离得到病原菌，对病原菌进行形态特征观察、致病性测定及其生物学特性研究。结果表明，该病原菌为Bipolarishawaiiensis。该菌能利用多种碳源和氮源，其中以蔗糖为最适碳源，以KNO3为最适氮源；菌丝生长最适温度为25-30℃；最适pH值7～9。菌丝的致死温度为70℃／15min。PDA平板药剂筛选结果表明，30％爱苗的抑菌效果最好，15％三唑酮的效果最差。

Study on Optimizing Nutrition and Fermentation Conditions for Compound <i>Bacillus spp.</i>

In order to improve the spore yield of compound Bacillus spp. (B. amyloliquefaciens, B. laterosporus and B. megaterium), the effects of nutrient conditions including carbon source, nitrogen source, mineral salt and fermentation conditions including the inoculum age, inoculation amount, loading volume of liquid and initial pH on the spore yield were studied. The results indicated that the optimized medium was glucoses 20 g/L, soybean meal 30.0 g/L, K2HPO4 1.0 g/L;fermentation temperature is 37&#8451;, the inoculum age 12 h, initial pH 7.0, 2% inoculation amount, loading volume of liquid 20 mL/250 mL. Under the optimized conditions of culture medium and fermentation for compound Bacillus spp., spore yield was 10.24 times more than the initial medium, and the spore formation rate reached more than 90%.

A 2-kb Mycovirus Converts a Pathogenic Fungus into a Beneficial Endophyte for Brassica Protection and Yield Enhancement

Mycoviruses are viruses that infect fungi,and hypovirulence-associated mycoviruses have the potential to control fungal diseases.However,it is unclear how mycovirus-mediated hypovirulent strains live and survive in the field,and no mycovirus has been applied for field crop protection.In this study,we found that a previously identified small DNA mycovirus(SsHADV-1)can convert its host,Sclerotinia sclerotiorum,from a typical necrotrophic pathogen to a beneficial endophytic fungus.SsHADV-1 downregulates the expression of key pathogenicity factor genes in S.sclerotiorum during infection.When growing in rapeseed,the SsHADV-1-infected strain DT-8 significantly regulates the expression of rapeseed genes involved in defense,hormone signaling,and circadian rhythm pathways.As a result,plant growth is promoted and disease resistance is enhanced.Field experiments showed that spraying DT-8 at the early flowering stage can reduce the disease severity of rapeseed stem rot by 67.6%and improve yield by 14.9%.Moreover,we discovered that SsHADV-1 could also infect other S.sclerotiorum strains on DT-8-inoculated plants and that DT-8 could be recovered from dead plants.These findings suggest that the mycoviruses may have the ability to shape the origin of endophytism.Our discoveries suggest that mycoviruses may influence the origin of endophytism and may also offer a novel strategy for disease control in which mycovirus-infected strains are used to improve crop health and release mycoviruses into the field.

Active DNA demethylation regulates MAMP-triggered immune priming in Arabidopsis

Plants recognize microbe-associated molecular patterns(MAMPs)to activate immune responses and defense priming to defend against pathogen infections.Transcriptional regulation of gene expression is crucial for plant immunity and is mediated by multiple factors,including DNA methylation.However,it remains unknown whether and how DNA demethylation contributes to immune responses in MAMPtriggered immunity.Here,we report that active DNA demethylation is required for MAMP-triggered immunity to bacterial pathogens.The rdd-2 triple mutant carrying mutations in ROS1,DML2,and DML3 that encode DNA glycosylases,which are key DNA demethylation enzymes,exhibits compromised immune responses triggered by the MAMPs fig22 and elf18.Genome-wide methylome analysis reveals that fig22 induces rapid and specific DNA demethylation in an RDD-dependent manner.The expression levels of salicylic acid signaling-related and phytoalexin biosynthesis-related genes are tightly associated with the fig22-induced promoter demethylation.The compromised accumulation of priming compounds and antimicrobial metabolites ultimately leads to a defense priming defect in the rdd-2 mutant.Our results reveal the critical role of active DNA demethylation in the MAMP-triggered immune response and provide unique insight into the molecular mechanism of fig22-modulated DNA demethylation.