Increasing Fusarium verticillioides resistance in maize by genomicsassisted breeding:Methods,progress,and prospects

Maize(Zea mays L.)is an indispensable crop worldwide for food,feed,and bioenergy production.Fusarium verticillioides(F.verticillioides)is a widely distributed phytopathogen and incites multiple destructive diseases in maize:seedling blight,stalk rot,ear rot,and seed rot.As a soil-,seed-,and airborne pathogen,F.verticillioides can survive in soil or plant residue and systemically infect maize via roots,contaminated seed,silks,or external wounds,posing a severe threat to maize production and quality.Infection triggers complex immune responses:induction of defense-response genes,changes in reactive oxygen species,plant hormone levels and oxylipins,and alterations in secondary metabolites such as flavonoids,phenylpropanoids,phenolic compounds,and benzoxazinoid defense compounds.Breeding resistant maize cultivars is the preferred approach to reducing F.verticillioides infection and mycotoxin contamination.Reliable phenotyping systems are prerequisites for elucidating the genetic structure and molecular mechanism of maize resistance to F.verticillioides.Although many F.verticillioides resistance genes have been identified by genome-wide association study,linkage analysis,bulkedsegregant analysis,and various omics technologies,few have been functionally validated and applied in molecular breeding.This review summarizes research progress on the infection cycle of F.verticillioides in maize,phenotyping evaluation systems for F.verticillioides resistance,quantitative trait loci and genes associated with F.verticillioides resistance,and molecular mechanisms underlying maize defense against F.verticillioides,and discusses potential avenues for molecular design breeding to improve maize resistance to F.verticillioides.

The peroxisomal matrix shuttling receptor Pex5 plays a role in FB1 production and virulence in Fusarium verticillioides

The peroxisomal matrix oxidase,catalase and peroxidase are imported peroxisomes through the shuttling receptors,which regulates the cellular oxidative homeostasis and function.Here,we report that PTS1 shuttling receptor FvPex5 is involved in the localization of PTS1,utilization of carbon sources and lipids,elimination ROS,cell wall stress,conidiation,fumonisin B_(1)(FB_(1))production,and virulence in maize pathogen Fusarium verticillioides.Significantly,differential expression of PTS1-,PTS2-,PEX-and FB_(1)toxin-related genes in wild type andΔFvpex5 mutant were examined by RNA-Seq analyses and confirmed by RT-PCR assay.In addition,different expression of PTS1 and PTS2 genes of theΔFvpex5 mutant were enriched in diverse biochemical pathways,such as carbon metabolism,nitrogen metabolism,lipid metabolism and the oxidation balance by combining GO and KEGG annotations.Overall,we showed that FvPex5 is involved in the regulation of genes associated with PTS,thereby affecting the oxidation balance,FB_(1)and virulence in F.verticillioides.The results help to clarify the functional divergence of Pex5 orthologs,and may provide a possible target for controlling F.verticillioides infections and FB_(1)biosynthesis.

Proteomic analysis of pathogen-responsive proteins from maize stem apoplast triggered by Fusarium verticillioides

During the attack of a pathogen, a variety of defense-associated proteins are released by the host plant in the apoplast to impede the perceived attack. This study utilized the mass spectrometry(LC-MS/MS) and label-free quantification method to analyze the apoplastic fluid(APF) from maize stalk and identified the proteins responsive to the Fusarium verticillioides infection. We have identified 742 proteins, and among these, 119 proteins were differentially accumulated(DAPs), i.e., 35 up-regulated, 18 down-regulated, and 66 proteins were only induced by the pathogen infection. The differentially accumulated proteins were analyzed for their Gene Ontology(GO) and Kyoto Encyclopedia of Gene and Genomes(KEGG) pathway enrichment. The highly enriched Biological Process(BP) term was the L-serine biosynthesis process, whereas the most enriched Molecular Function(MF) term was the cysteine-type endopeptidase inhibitor activity. It was also found that the pathways related to the biosynthesis of amino acid, biosynthesis of secondary metabolites, protein processing in the endoplasmic reticulum, and carbohydrate metabolic pathways were significantly enriched. Moreover, 61 out of 119 differentially accumulated proteins were predicted as secretory proteins. The secretory pathways analysis showed that a greater number of proteins were secreted through the conventional secretion system compared to the unconventional secretion system. The identified secreted proteins were related to a variety of pathways in defense responses including cell redox homeostasis, cell wall modification, signal transduction, carbohydrate metabolism, binding proteins(metal ion binding, RNA binding and heme-binding), maintenance and stabilization of other proteins, indicating a complex response from the plant to the fungal infection. Our data suggested that a number of host proteins belonging to various pathways have been modulated in the apoplastic region.

旱黄瓜茎基腐病菌鉴定及其生物学特性

为明确昌黎旱黄瓜茎基腐病的病原菌,采用组织分离法和针刺法对其病原物进行分离培养和致病性测定,通过形态学、ITS序列分析方法鉴定旱黄瓜茎基腐病原菌种类后对病原菌的生物学特性进行了研究。结果表明:旱黄瓜茎基腐病的病原菌为拟轮枝镰孢菌(Fusarium verticillioides);该病菌菌丝最适生长温度为30℃,最适pH为6.0,最适碳源为葡萄糖,最适氮源为NH_(4)NO_(3),致死温度为69℃,10 min;大型分生孢子生长最适温度为25℃,小型分生孢子生长最适温度为30℃;两种孢子生长的最适pH,碳源,氮源均为5.0,蔗糖,NH_(4)NO_(3)。