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.

HY5-HDA9 orchestrates the transcription of HsfA2 to modulate salt stress response in Arabidopsis

Integration of light signaling and diverse abiotic stress responses contribute to plant survival in a changing environment.Some reports have indicated that light signals contribute a plant’s ability to deal with heat,cold,and stress.However,the molecular link between light signaling and the saltresponse pathways remains unclear.We demonstrate here that increasing light intensity elevates the salt stress tolerance of plants.Depletion of HY5,a key component of light signaling,causes Arabidopsis thaliana to become salinity sensitive.Interestingly,the small heat shock protein(sHsp)family genes are upregulated in hy5-215 mutant plants,and HsfA 2 is commonly involved in the regulation of these sH sps.We found that HY5directly binds to the G-box motifs in the HsfA2promoter,with the cooperation of HISTONE DEACETYLASE 9(HDA9),to repress its expression.Furthermore,the accumulation of HDA9 and the interaction between HY5 and HDA9 are significantly enhanced by salt stress.On the contrary,high temperature triggers HY5 and HDA9 degradation,which leads to dissociation of HY5-HDA9from the HsfA2 promoter,thereby reducing salt tolerance.Under salt and heat stress conditions,fine tuning of protein accumulation and an interaction between HY5 and HDA9 regulate HsfA2 expression.This implies that HY5,HDA9,and HsfA2play important roles in the integration of light signaling with salt stress and heat shock response.

Repress,on of MYBL2 by Both microRNA858a and HY5 Leads to the Activation of Anthocyanin Biosynthetic Pathway in Arabidopsis

Extensive studies in various plants show that the anthocyanin biosynthetic process is affected by environmental factors and regulated by many transcription factors through sophisticated regulatory networks. However, it remains largely unclear about the roles of microRNA in this process. Here, we demonstrate that miR858a is a positive regulator of anthocyanin biosynthesis in Arabidopsis seedlings. Overexpression of miR858a enhances the accumulation of anthocyanins, whereas the reduced miR858a activity results in low levels of anthocyanins in STTM858 transgenic plants. We found that miR858a inhibits the expression of MYBL2, a key negative regulator of anthocyanin biosynthesis, by translational repression. In addition, ELONGATED HYPOCOTYL 5 （HYS） was shown to directly bind the MYBL2 promoter and represses its expression via specific histone modifications. Interestingly, we found that miR858a exhibits light- responsive expression in an HY5-dependent manner. Together, these results delineate the HY5- MIR858a-MYBL2 loop as a cellular mechanism for modulating anthocyanin biosynthesis, suggesting that integration of transcriptional and posttranscriptional regulation is critical for governing proper anthocyanin accumulation in response to light and other environmental factors.

A flow cytometer based protocol for quantitative analysis of bloom-forming cyanobacteria(Microcystis) in lake sediments

A quantitative protocol for the rapid analysis of Microcystis cells and colonies in lake sediment was developed using a modified flow cytometer, the CytoSense. For cell enumeration, diluted sediment samples containing Microcystis were processed with sonication to disintegrate colonies into single cells. An optimized procedure suggested that 5 mg dw （dry weight）/mL dilution combined with 200 W x 2 min sonication yielded the highest counting efficiency. Under the optimized determination conditions, the quantification limit of this protocol was 3.3x104 cells/g dw. For colony analysis, Microcystis were isolated from the sediment by filtration. Colony lengths measured by flow cytometry were similar to those measured by microscopy for the size range of one single cell to almost 400 ~tm in length. Moreover, the relationship between colony size and cell number was determined for three Microcystis species, including Microcystisflos-aquae, M. aeruginosa and M. wessenbergii. Regression formulas were used to calculate the cell numbers in different- sized colonies. The developed protocol was applied to field sediment samples from Lake Taihu. The results indicated the potential and applicability of flow cytometry as a tool for the rapid analysis of benthic Microcystis. This study provided a new capability for the high frequency monitoring of benthic overwintering and population dynamics of this bloom-forming cyanobacterium.

HY5 regulates light-responsive transcription of microRNA163 to promote primary root elongation in Arabidopsis seedlings

MicroRNAs(miRNAs)play key roles in the post-transcriptional regulation of gene expression in plants.Many miRNAs are responsive to environmental signals.Light is the first environmental signal perceived by plants after emergence from the soil.However,less is known about the roles and regulatory mechanism of miRNAs in response to light signal.Here,using small RNA sequencing,we determined that miR163 is significantly rapidly induced by light signaling in Arabidopsis thaliana seedlings.The light-inducible response of miR163 functions genetically downstream of LONG HYPOCOTYL 5(HY5),a central positive regulator of photomorphogenesis.HY5 directly binds to the two G/C-hybrid elements in the miR163 promoter with unequal affinity;one of these elements,which is located next to the transcription start site,plays a major role in light-induced expression of miR163.Overexpression of miR163 rescued the defective primary root elongation of hy5 seedlings without affecting lateral root growth,whereas overexpressing of miR163 target PXMT1 inhibited primary root elongation.These findings provide insight into understanding the post-transcriptional regulation of root photomorphogenesis mediated by the HY5-miR163-PXMT1 network.

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.

Predictors for Treatment Outcomes in Patients with Multi-drug Resistant Tuberculosis — China, 2018–2020

Summary What is already known about this topic?Multi-drug resistant tuberculosis(MDR-TB)is a critical global public health problem.What is added by this report?Sputum cultures and lung images show a strong association with treatment outcomes,serving as a multi-dimensional approach to identify MDR-TB patients with poor outcomes.

SICKLE represses photomorphogenic development of Arabidopsis seedlings via HY5-and PIF4-mediated signaling

Arabidopsis CONSTITUTIVELY PHOTOMORPHO GENIC1(COP1)and PHYTOCHROME INTERACTING FACTORs(PIFs)are negative regulators,and ELONGATED HYPOCOTYL5(HY5)is a positive regulator of seedling photomorphogenic development.Here,we report that SICKLE(SIC),a proline rich protein,acts as a novel negative regulator of photomorphogenesis.HY5 directly binds the SIC promoter and activates SIC expression in response to light.In turn,SIC physically interacts with HY5 and interferes with its transcriptional regulation of downstream target genes.Moreover,SIC interacts with PIF4 and promotes PIF4-activated transcription of itself.Interestingly,SIC is targeted by COP1 for 26S proteasomemediated degradation in the dark.Collectively,our data demonstrate that light-induced SIC functions as a brake to prevent exaggerated light response via mediating HY5 and PIF4 signaling,and its degradation by COP1 in the dark avoid too strong inhibition on photomorphogenesis at the beginning of light exposure.