Genetic variation in ZmSO contributes to ABA response and drought tolerance in maize seedlings

Water scarcity impairs maize growth and yield.Identification and deployment of superior droughttolerance alleles is desirable for the genetic improvement of stress tolerance in maize.Our previous study revealed that maize sulfite oxidase(SO) catalyzes the oxidation of sulfite to sulfate and may be involved in drought response.But it was unclear whether the natural variation in Zm SO is directly associated with the drought resistance of maize.In the present study,we showed that Zm SO was associated with drought tolerance in maize seedlings,using gene association analysis and a transgene approach.A 14-bp insertion variation,containing two ABA-responsive elements,in the promoter region of Zm SO conferred ABAinducible expression,leading to increased drought tolerance.Genetic selection of this favorable allele increased drought tolerance.This study has identified elite alleles associated with sulfur metabolism for improving maize drought resistance.

Growth Effect of Biennial Seedlings of Half-sib Families of Cyclobalanopsis glauca

The seedling height and ground diameter of 42 half-sib families of biennial Cyclobalanopsis glauca were investigated and compared. The results showed that there were extremely significant differences between different families in the terms of seedling height and ground diameter. According to the seedling height and ground diameter, families 39, 27, 28 and 19 of C. glauca were superior to other families at the seedling stage.

Monthly Changes in the Resin Yield of Semi-sib Families of Pinus elliottii

Monthly changes in the resin yield of semi-sib families of Pinus elliottii during 2013-2015 were studied.The results showed that from April to October,the resin yield of the P.elliottii families was the lowest in April and the highest in July.There were significant differences between various families in terms of resin yield.The change of resin yield was closely related to temperature,and the higher the temperature was,the higher the resin yield was.P.elliottii mainly produced resin from June to September.

Heritability Analysis of Growth Traits and Selection of Semi-sib Families of Pinus elliottii

Growth traits of semi-sib families of Pinus elliottii were studied.The results showed that there were extremely significant differences between the P.elliottii families in terms of tree height,DBH and volume( P < 0.01),and the families could be selected effectively.Both family heritability and single plant heritability of growth traits of P.elliottii were high.The family heritability of tree height,DBH and volume was 0.799,0.779 and 0.770 respectively,and their single plant heritability was 0.683,0.829 and 0.742 respectively.Among them,the family heritability of tree height was the highest,while the single plant heritability of DBH was the highest.The Duncan analysis of growth traits of the P.elliottii families revealed that families 12,7,15,4 and 6 were superior families and can be used as high-yield families.

Enhancing maize's nitrogen-fixing potential through ZmSBT3, a gene suppressing mucilage secretion∞

Maize(Zea mays)requires substantial amounts of nitrogen,posing a challenge for its cultivation.Recent work discovered that some ancient Mexican maize landraces harbored diazotrophic bacteria in mucilage secreted by their aerial roots.To see if this trait is retained in modern maize,we conducted a field study of aerial root mucilage(ARM)in 258 inbred lines.We observed that ARM secretion is common in modern maize,but the amount significantly varies,and only a few lines have retained the nitrogen‐fixing traits found in ancient landraces.The mucilage of the high‐ARM inbred line HN5‐724 had high nitrogen‐fixing enzyme activity and abundant diazotrophic bacteria.Our genome‐wide association study identified 17 candidate genes associated with ARM across three environments.Knockouts of one candidate gene,the subtilase family gene ZmSBT3,confirmed that it negatively regulates ARM secretion.Notably,the ZmSBT3 knockout lines had increased biomass and total nitrogen accumulation under nitrogen‐free culture conditions.High ARM was associated with three ZmSBT3 haplotypes that were gradually lost during maize domestication,being retained in only a few modern inbred lines such as HN5‐724.In summary,our results identify ZmSBT3 as a potential tool for enhancing ARM,and thus nitrogen fixation,in maize.

Natural variation in maize gene ZmSBR1 confers seedling resistance to Fusarium verticillioides

Maize seedling blight caused by Fusarium verticillioides is a widely occurring maize disease,but the genetics and mechanisms of resistance are not well understood.In this study,GWAS performed by MLM and 3VmrMLM identified 40 and 20 QTNs,associated with seedling blight resistance.These methods identified 49 and 36 genes,respectively.Functional verification of candidate gene ZmSBR1 identified by both methods showed that the resistance of a mutant line to seedling blight decreased by 0.37 grade points after inoculation with F.verticillioides,compared with the WT.The length of the stem rot lesion caused by F.verticillioides increased by 86%in mutant seedlings,and the relative length of the adult plant stalk rot increased by 35%in mutant plants compared to the wild type after inoculation with Fusarium graminearum.Transcriptome analysis showed that expression of defense-related genes after inoculation was down-regulated in the mutant compared to the wild type,synthesis of secondary metabolites associated with resistance was reduced,and the immune response triggered by PAMP decreased,resulting in decreased resistance of mutant maize seedlings.Candidate gene association analysis showed that most maize inbred lines carried the susceptible haplotype.A functional PCR marker was developed.The results demonstrated that ZmSBR1 conferred resistance to multiple Fusarium diseases at the seedling and adult growth stages and had important application value in breeding.

MicroRNAs Are Involved in Maize Immunity Against Fusarium verticillioides Ear Rot

Fusarium ear rot(FER)caused by Fusarium verticillioides is one of the most common diseases affecting maize production worldwide.FER results in severe yield losses and grain contamination with health-threatening mycotoxins.Although most studies to date have focused on comprehensive analysis of gene regulation in maize during defense responses against F.verticillioides infection,less is known about the role of micro RNAs(mi RNAs)in this process.We used deep sequencing to compare small RNA libraries from the maize kernels of susceptible(N6)or resistant(BT-1)inbred lines from uninfected plants and upon F.verticillioides infection.We found that pathogen exposure was accompanied by dynamic alterations in expression levels of multiple mi RNAs,including new members of previously annotated mi RNA families.A combination of transcriptomic,degradomic,and bioinformatics analyses revealed that F.verticillioides-responsive mi RNAs and their potential target genes displayed opposite expression patterns in the susceptible and resistant genotypes.Functional category analysis uncovered preferential enrichment of the pathogen-responsive mi RNAs and their targets in the phenylpropanoid metabolic processes,plant–pathogen interactions,and plant phytohormone signal transduction pathways.Furthermore,transgenic maize plants overexpressing mi R408 b exhibited reduced resistance to F.verticillioides infection in a susceptible maize line.These findings provide new insights into the regulatory roles of mi RNAs in maize immunity against FER and new resources for breeding disease resistance into maize.