The ZmbHLH47-ZmSnRK2.9 Module Promotes Drought Tolerance in Maize.

Drought stress globally poses a significant threat to maize (Zea mays L.) productivity and the underlying molecular mechanisms of drought tolerance remain elusive. In this study, we characterized ZmbHLH47, a basic helix-loop-helix (bHLH) transcription factor, as a positive regulator of drought tolerance in maize. ZmbHLH47 expression was notably induced by both drought stress and abscisic acid (ABA). Transgenic plants overexpressing ZmbHLH47 displayed elevated drought tolerance and ABA responsiveness, while the zmbhlh47 mutant exhibited increased drought sensitivity and reduced ABA sensitivity. Mechanistically, it was revealed that ZmbHLH47 could directly bind to the promoter of ZmSnRK2.9 gene, a member of the subgroup III SnRK2 kinases, activating its expression. Furthermore, ZmSnRK2.9-overexpressing plants exhibited enhanced ABA sensitivity and drought tolerance, whereas the zmsnrk2.9 mutant displayed a decreased sensitivity to both. Notably, overexpressing ZmbHLH47 in the zmsnrk2.9 mutant closely resembled the zmsnrk2.9 mutant, indicating the importance of the ZmbHLH47-ZmSnRK2.9 module in ABA response and drought tolerance. These findings provided valuable insights and a potential genetic resource for enhancing the environmental adaptability of maize.

Gene pyramiding of ZmGLK36 and ZmGDIα-hel for rough dwarf disease resistance in maize.

Maize rough dwarf disease (MRDD) caused by pathogenic viruses in the genus Fijivirus in the family Reoviridae is one of the most destructive diseases in maize. The pyramiding of effective resistance genes into maize varieties is a potential approach to reduce the damage resulting from the disease. Two major quantitative trait loci (QTLs) (qMrdd2 and qMrdd8) have been previously identified. The resistance genes ZmGLK36 and ZmGDIα-hel have also been cloned with the functional markers Indel-26 and IDP25K, respectively. In this study, ZmGLK36 and ZmGDIα-hel were introgressed to improve MRDD resistance of maize lines (Zheng58, Chang7-2, B73, Mo17, and their derived hybrids Zhengdan958 and B73 × Mo17) via marker-assisted selection (MAS). The converted lines and their derived hybrids, carrying one or two genes, were evaluated for MRDD resistance using artificial inoculation methods. The double-gene pyramiding lines and their derived hybrids exhibited increased resistance to MRDD compared to the monogenic lines and the respective hybrids. The genetic backgrounds of the converted lines were highly similar (90.85-98.58%) to the recurrent parents. In addition, agronomic trait evaluation demonstrated that pyramiding lines with one or two genes and their derived hybrids were not significantly different from the recurrent parents and their hybrids under nonpathogenic stress, including period traits (tasseling, pollen shedding, and silking), yield traits (ear length, grain weight per ear and 100-kernel weight) and quality traits (protein and starch content). There were differences in plant architecture traits between the improved lines and their hybrids. This study illustrated the successful development of gene pyramiding for improving MRDD resistance by advancing the breeding process. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01466-9.

The ZmbHLH32-ZmIAA9-ZmARF1 module regulates salt tolerance in maize.

The growth and productivity of maize (Zea mays), along with other crop plants, can be significantly hindered by salt stress. Nevertheless, the precise molecular mechanism underlying salt tolerance in maize has yet to be fully elucidated. Hence, it was attempted to identify ZmIAA9, a member of the maize Aux/IAA gene family, as a positive regulator of salt tolerance in maize, which was accompanied by the increased ROS detoxification and elevated transcript abundances of ROS scavenging genes. Molecular and biochemical assays have provided compelling evidence that ZmbHLH32, a transcription factor belonging to the bHLH family, was capable of binding directly to the promoter region of ZmIAA9, thereby activating its expression. This interaction between ZmbHLH32 and ZmIAA9 could be critical for the regulation of salt tolerance in maize. As expected, overexpression of ZmbHLH32 led to the enhanced salt tolerance. In contrast, decreased salt tolerance was attained after application of knockout mutants of ZmbHLH32. Furthermore, ZmARF1, which could act as a downstream of ZmIAA9, was found to physically interact with ZmIAA9 and repress the expression levels of ROS scavenging genes. Thus, our work uncovers a novel mechanism of ZmbHLH32-ZmIAA9-ZmARF1 module-mediated salt tolerance in maize, which can be exploited for breeding salt-tolerant maize varieties.

A transcription factor ZmGLK36 confers broad resistance to maize rough dwarf disease in cereal crops.

Maize rough dwarf disease (MRDD), caused by maize rough dwarf virus (MRDV) or rice black-streaked dwarf virus (RBSDV), seriously threatens worldwide production of all major cereal crops, including maize, rice, wheat and barley. Here we report fine mapping and cloning of a previously reported major quantitative trait locus (QTL) (qMrdd2) for RBSDV resistance in maize. Subsequently, we show that qMrdd2 encodes a G2-like transcription factor named ZmGLK36 that promotes resistance to RBSDV by enhancing jasmonic acid (JA) biosynthesis and JA-mediated defence response. We identify a 26-bp indel located in the 5' UTR of ZmGLK36 that contributes to differential expression and resistance to RBSDV in maize inbred lines. Moreover, we show that ZmDBF2, an AP2/EREBP family transcription factor, directly binds to the 26-bp indel and represses ZmGLK36 expression. We further demonstrate that ZmGLK36 plays a conserved role in conferring resistance to RBSDV in rice and wheat using transgenic or marker-assisted breeding approaches. Our results provide insights into the molecular mechanisms of RBSDV resistance and effective strategies to breed RBSDV-resistant cereal crops.

A large deletion conferring pale green leaves of maize.

BACKGROUND: The structural basis of chloroplast and the regulation of chloroplast biogenesis remain largely unknown in maize. Gene mutations in these pathways have been linked to the abnormal leaf color phenotype observed in some mutants. Large scale structure variants (SVs) are crucial for genome evolution, but few validated SVs have been reported in maize and little is known about their functions though they are abundant in maize genomes. RESULTS: In this research, a spontaneous maize mutant, pale green leaf-shandong (pgl-sd), was studied. Genetic analysis showed that the phenotype of pale green leaf was controlled by a recessive Mendel factor mapped to a 156.8-kb interval on the chromosome 1 delineated by molecular markers gy546 and gy548. There were 7 annotated genes in this interval. Reverse transcription quantitative PCR analysis, SV prediction, and de novo assembly of pgl-sd genome revealed that a 137.8-kb deletion, which was verified by Sanger sequencing, might cause the pgl-sd phenotype. This deletion contained 5 annotated genes, three of which, including Zm00001eb031870, Zm00001eb031890 and Zm00001eb031900, were possibly related to the chloroplast development. Zm00001eb031870, encoding a Degradation of Periplasmic Proteins (Deg) homolog, and Zm00001eb031900, putatively encoding a plastid pyruvate dehydrogenase complex E1 component subunit beta (ptPDC-E1-ß), might be the major causative genes for the pgl-sd mutant phenotype. Plastid Degs play roles in protecting the vital photosynthetic machinery and ptPDCs provide acetyl-CoA and NADH for fatty acid biosynthesis in plastids, which were different from functions of other isolated maize leaf color associated genes. The other two genes in the deletion were possibly associated with DNA repair and disease resistance, respectively. The pgl-sd mutation decreased contents of chlorophyll a, chlorophyll b, carotenoids by 37.2%, 22.1%, and 59.8%, respectively, and led to abnormal chloroplast. RNA-seq revealed that the transcription of several other genes involved in the structure and function of chloroplast was affected in the mutant. CONCLUSIONS: It was identified that a 137.8-kb deletion causes the pgl-sd phenotype. Three genes in this deletion were possibly related to the chloroplast development, which may play roles different from that of other isolated maize leaf color associated genes.

Research Progress on the Mechanism of Salt Tolerance in Maize: A Classic Field That Needs New Efforts.

Maize is the most important cereal crop globally. However, in recent years, maize production faced numerous challenges from environmental factors due to the changing climate. Salt stress is among the major environmental factors that negatively impact crop productivity worldwide. To cope with salt stress, plants developed various strategies, such as producing osmolytes, increasing antioxidant enzyme activity, maintaining reactive oxygen species homeostasis, and regulating ion transport. This review provides an overview of the intricate relationships between salt stress and several plant defense mechanisms, including osmolytes, antioxidant enzymes, reactive oxygen species, plant hormones, and ions (Na+, K+, Cl-), which are critical for salt tolerance in maize. It addresses the regulatory strategies and key factors involved in salt tolerance, aiming to foster a comprehensive understanding of the salt tolerance regulatory networks in maize. These new insights will also pave the way for further investigations into the significance of these regulations in elucidating how maize coordinates its defense system to resist salt stress.

Molecular Mechanism of Gibberellins in Mesocotyl Elongation Response to Deep-Sowing Stress in Sweet Maize.

Uneven germination is still a common problem in sweet maize planting. The mesocotyl is a key driver for ground-breaking sweet maize, and deep-sowing has a longer mesocotyl. However, the physiological and molecular mechanisms of sweet maize mesocotyl elongation in response to deep-sowing remain unknown. Here we found that sweet maize inbred line Ltx05 could obtain longer mesocotyls in deep soil of 10 cm depth, and that 20 mg/L GA3 was the optimal concentration to promote mesocotyl elongation and seedling emergence. Microstructure observation showed that the longitudinal cell length of mesocotyl at 10 cm sowing depth was significantly longer than that of 1 cm. Transcriptome analysis showed that microtubule process related differentially expressed genes may contribute to the longitudinal cell elongation. The content of GAs in the mesocotyl at 10 cm sowing depth was markedly higher than that of 1 cm. Combining transcriptome data and qRT-PCR at different developmental stages, ZmGA20ox1, ZmGA20ox4 and ZmGA20ox5 were identified as three positive regulation candidate genes during mesocotyl elongation under deep-sowing conditions, and this was further confirmed by the significant elongation of the hypocotyl in heterologous transformation of Arabidopsis thaliana. These results lay a foundation for improving the ability of sweet maize to tolerate deep-sowing stress and improving the breeding of excellent deep-sowing-tolerant germplasms.

Enrichments/Derichments of Root-Associated Bacteria Related to Plant Growth and Nutrition Caused by the Growth of an EPSPS-Transgenic Maize Line in the Field.

During the past decades, the effects of the transgenic crops on soil microbial communities have aroused widespread interest of scientists, which was mainly related to the health and growth of plants. In this study, the maize root-associated bacterial communities of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) transgenic glyphosate-tolerant (GT) maize line CC-2 (CC2) and its recipient variety Zhengdan958 (Z958) were compared at the tasseling and flowering stages by high-throughput sequencing of V3-V4 hypervariable regions of 16S rRNA gene (16S rDNA) amplicons via Illumina MiSeq. In addition, real-time quantitative PCR (qPCR) was also performed to analyze the nifH gene abundance between CC2 and Z958. Our results showed no significant difference in alpha/beta diversity of root-associated bacterial communities at the tasseling or flowering stage between CC2 and Z958 under field growth conditions. The relative abundances of the genera Bradyrhizobium and Bacillus including species B. cereus and B. muralis were significantly lower in the roots of CC2 than that of Z985 under field conditions. Both these species are regarded as plant growth promoting bacteria (PGPB), as they belong to both nitrogen-fixing and phosphate-solubilizing bacterial genera. The comparison of the relative abundance of nitrogen-fixing/phosphate-solubilizing bacteria at the class, order or family levels indicated that only one class Bacilli, one order Bacillales and one family Bacillaceae were found to be significantly lower in the roots of CC2 than that of Z985. These bacteria were also enriched in the roots and rhizospheric soil than in the surrounding soil at both two stages. Furthermore, the class Betaproteobacteria, the order Burkholderiales, the family Comamonadaceae, and the genus Acidovorax were significantly higher in the roots of CC2 than that of Z985 at the tasseling stage, meanwhile the order Burkholderiales and the family Comamonadaceae were also enriched in the roots than in the rhizospheric soil at both stages. Additionally, the nifH gene abundance at the tasseling stage in the rhizosphere soil also showed significant difference. The relative abundance of nifH gene was higher in the root samples and lower in the surrounding soil, which implicated that the roots of maize tend to be enriched in nitrogen-fixing bacteria.

Phosphatidate phosphatase Pah1 has a role in the hyphal growth and virulence of Candida albicans.

Phosphatidate phosphatases play essential roles in lipid metabolism by converting phosphatidic acid to diacylglycerol. Here, we have investigated the roles of a phosphatidate phosphatase, Pah1, in the fungal pathogen Candida albicans. Deleting PAH1 causes multiple phenotypes, especially severe hyphal defects, increased sensitivity to cell wall stress, and reduced virulence in mice. By qPCR, we detected a significant downregulation of hyphal-specific genes including two key hyphal-promoting genes UME6 and HGC1. Overexpression of UME6 in pah1Δ/Δ cells largely restored the hyphal growth, indicating that the reduced expression of UME6 is primarily responsible for the hyphal defects. We also detected decreased expression of three hyphal-promoting transcription factors EFG1, FLO8, and CPH1 in pah1 mutants, consistent with the reduced expression of UME6. Furthermore, the pah1Δ/Δ mutant exhibited increased sensitivity to cell wall stress. During systemic infection of mice, the mutant showed significantly impaired ability to colonize the kidney and to kill the host. Together, C. albicans PAH1 plays an important role in hyphal growth, adaptability to environmental stresses, and virulence. Thus, Pah1 could be targeted for the development of new antifungal drugs.

Blocking ß-1,6-glucan synthesis by deleting KRE6 and SKN1 attenuates the virulence of Candida albicans.

ß-1,6-glucan is an important component of the fungal cell wall. The ß-1,6-glucan synthase gene KRE6 was thought to be essential in the fungal pathogen Candida albicans because it could not be deleted in previous efforts. Also, the role of its homolog SKN1 was unclear because its deletion caused no defects. Here, we report the construction and characterization of kre6Δ/Δ, skn1Δ/Δ and kre6Δ/Δ skn1Δ/Δ mutants in C. albicans. While deleting KRE6 or SKN1 had no obvious phenotypic consequence, deleting both caused slow growth, cell separation failure, cell wall abnormalities, diminished hyphal growth, poor biofilm formation and loss of virulence in mice. Furthermore, the GPI-linked cell surface proteins Hwp1 and the invasin Als3 or Ssa1 were not detected in kre6Δ/Δ skn1Δ/Δ mutant. In GMM medium, RT-qPCR and western blotting revealed a constitutive expression of KRE6 and growth conditions-associated activation of SKN1. Like many hypha-specific genes, SKN1 is repressed by Nrg1, but its activation does not involve the transcription factor Efg1. Dysregulation of SKN1 reduces C. albicans ability to damage epithelial and endothelial cells and attenuates its virulence. Given the vital role of ß-1,6-glucan synthesis in C. albicans physiology and virulence, Kre6 and Skn1 are worthy targets for developing antifungal agents.

Combined linkage and association mapping reveal QTL for host plant resistance to common rust (Puccinia sorghi) in tropical maize.

BACKGROUND: Common rust, caused by Puccinia sorghi, is an important foliar disease of maize that has been associated with up to 50% grain yield loss. Development of resistant maize germplasm is the ideal strategy to combat P. sorghi. RESULTS: Association mapping performed using a mixed linear model (MLM), integrating population structure and family relatedness identified 25 QTL (P < 3.12 × 10- 5) that were associated with resistance to common rust and distributed on chromosomes 1, 3, 5, 6, 8, and 10. We identified three QTLs associated with all three disease parameters (final disease rating, mean disease rating, and area under disease progress curve) located on chromosomes 1, 3, and 8. A total of 5 QTLs for resistance to common rust were identified in the RIL population. Nine candidate genes located on chromosomes 1, 5, 6, 8, and 10 for resistance to common rust associated loci were identified through detailed annotation. CONCLUSIONS: Using a diverse set of inbred lines genotyped with high density markers and evaluated for common rust resistance in multiple environments, it was possible to identify QTL significantly associated with resistance to common rust and several candidate genes. The results point to the need for fine mapping common rust resistance by targeting regions identified in common between this study and others using diverse germplasm.

Exogenous Pi supplementation improved the salt tolerance of maize (Zea mays L.) by promoting Na+ exclusion.

The mechanism of phosphate (Pi)-mediated salt tolerance in maize is poorly understood. In this study, the effects of Pi (H2PO4-) on the salt tolerance of two contrasting genotypes was investigated in a pot experiment. We discovered that the application of 3 mM Pi could alleviate salt injury caused by 200 mM NaCl. High amounts of compatible solutes and low amounts of reactive oxygen species (ROS) were also observed under Pi application. Consistent with the increased tolerance, the total number of roots and the growth of shoots increased to relieve salt stress. This phenomenon could be associated with the observed increased expression of nitrate transporters. Furthermore, the seedlings presented a negative relationship between sodium (Na+) and Pi (low Na+ content and high Pi content), which is related to the genes ZmNHX1, ZmPHT1;8, and ZmPHT1;9, indicating that the exclusion of Na+ was promoted by high Pi uptake. However, high Na+ and low potassium (K+) efflux were detected in the roots, and these were positively correlated with two K+ transporters. These observations indicate that Na+ exclusion was directly induced by high K+ retention rather than Pi absorption. We conclude that maize salt tolerance increased in response to Pi application by promoting Na+ exclusion.

Key factors identified by proteomic analysis in maize (Zea mays L.) seedlings' response to long-term exposure to different phosphate levels.

BACKGROUND: Maize seedlings are constantly exposed to inorganic phosphate (Pi)-limited environments. To understand how maize cope with low Pi (LP) and high Pi (HP) conditions, physiological and global proteomic analysis of QXN233 genotype were performed under the long-term Pi starvation and supplementation. METHODS: We investigated the physiological response of QXN233 genotype to LP and HP conditions and detected the changes in ion fluxes by non-invasive micro-test technology and gene expression by quantitative real-time polymerase chain reaction. QXN233 was further assessed using vermiculite assay, and then proteins were isolated and identified by nano-liquid chromatography-mass spectrometry. RESULTS: A negative relationship was observed between Na+ and Pi, and Na+ efflux was enhanced under HP condition. Furthermore, a total of 681 and 1374 were identified in the leaves and roots, respectively, which were mostly involved in metabolism, ion transport, and stress response. Importantly, several key Pi transporters were identified for breeding potential. Several ion transporters demonstrated an elaborate interplay between Pi and other ions, together contributing to the growth of QXN233 seedlings. CONCLUSION: The results from this study provide insights into the response of maize seedlings to long-term Pi exposure.

Prospective investigation of folic acid supplements before and during early pregnancy and paediatric and adult cancers in the Chinese children and families cohort: a pilot study in a sample of rural and urban families.

OBJECTIVE: To determine the feasibility of long-term prospective follow-up and ascertainment of cancer in offspring and mothers from the 1993-1995 Chinese Community Intervention Program that provided folic acid supplements before and during early pregnancy to reduce neural tube defects. DESIGN: Feasibility pilot study for a prospective cohort study. SETTING: Families residing during 2012-2013 in one rural and one urban county from 21 counties in 3 provinces in China included in the Community Intervention Program campaign. PARTICIPANTS: The feasibility study targeted 560 families, including 280 from the rural and 280 from the urban county included in the large original study; about half of mothers in each group had taken and half had not taken folic acid supplements. INTERVENTION: The planned new study is observational. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary: incidence of paediatric cancers in offspring; secondary: other chronic diseases in offspring and chronic diseases in mothers RESULTS: Only 3.4% of pilot study families could not be found, 3.9% had moved out of the study area and 8.8% refused to participate. Interviews were completed by 82% of mothers, 79% of fathers and 83% of offspring in the 560 families. Almost all mothers and offspring who were interviewed also participated in anthropometric measurements. We found notable urban-rural differences in sociodemographic and lifestyle characteristics of the parents, but fewer differences among the offspring. In eight catchment area hospitals, we identified a broad range of paediatric cancers diagnosed during 1994-2013, although paediatric brain tumours, lymphomas and rarer cancers were likely under-represented. CONCLUSIONS: Overall, 20 years after the original Community Intervention Program, the pilot study achieved high levels of follow-up and family member interview participation, and identified substantial numbers of paediatric malignancies during 1994-2013 in catchment area hospitals. Next steps and strategies for overcoming limitations are described.

Characterization of Pph3-mediated dephosphorylation of Rad53 during methyl methanesulfonate-induced DNA damage repair in Candida albicans.

Genotoxic stress causes DNA damage or stalled DNA replication and filamentous growth in the pathogenic fungus Candida albicans The DNA checkpoint kinase Rad53 critically regulates by phosphorylation effectors that execute the stress response. Rad53 itself is activated by phosphorylation and inactivated by dephosphorylation. Previous studies have suggested that the phosphatase Pph3 dephosphorylates Rad53. Here, we used mass spectrometry and mutagenesis to identify Pph3 dephosphorylation sites on Rad53 in C. albicans We found that serine residues 351, 461 and 477, which were dephosphorylated in wild-type cells during the recovery from DNA damage caused by methyl methanesulfonate (MMS), remained phosphorylated in pph3Δ/Δ cells. Phosphomimetic mutation of the three residues (rad53-3D) impaired Rad53 dephosphorylation, exit from cell cycle arrest, dephosphorylation of two Rad53 effectors Dun1 and Dbf4, and the filament-to-yeast growth transition during the recovery from MMS-induced DNA damage. The phenotypes observed in the rad53-3D mutant also occurred in the pph3Δ/Δ mutant. Together, our findings reveal a molecular mechanism by which Pph3 controls DNA damage response in C. albicans.

Comparative transcript profiling of maize inbreds in response to long-term phosphorus deficiency stress.

Maize (Zea mays L.) is an important food and energy crop, and low phosphate (Pi) availability is one of the major constraints in maize production worldwide. Plants adapt suitably to acclimate to low Pi stress. However, the underlying molecular mechanism of Pi deficiency response is still unclear. In this study, comparative transcriptomic analyses were conducted to investigate the differences of transcriptional responses in two maize genotypes with different tolerances to low phosphorus (LP) stress. LP-tolerant genotype QXN233 maintained higher P and Pi levels in shoots than LP-sensitive genotype QXH0121 suffering from Pi deficiency at seedling stage. Moreover, the transcriptomic analysis identified a total of 1391 Pi-responsive genes differentially expressed between QXN233 and QXH0121 under LP stress. Among these genes, 468 (321 up- and 147 down-regulated) were identified in leaves, and 923 (626 up- and 297 down-regulated) were identified in roots. These Pi-responsive genes were involved in various metabolic pathways, the biosynthesis of secondary metabolites, ion transport, phytohormone regulation, and other adverse stress responses. Consistent with the differential tolerance to LP stress, five maize inorganic Pi transporter genes were more highly up-regulated in QXN233 than in QXH0121. Results provide important information to further study the changes in global gene expression between LP-tolerant and LP-sensitive maize genotypes and to understand the molecular mechanisms underlying maize's long-term response to Pi deficiency.

Genome-Wide Association Study and QTL Mapping Reveal Genomic Loci Associated with Fusarium Ear Rot Resistance in Tropical Maize Germplasm.

Fusarium ear rot (FER) incited by Fusarium verticillioides is a major disease of maize that reduces grain quality globally. Host resistance is the most suitable strategy for managing the disease. We report the results of genome-wide association study (GWAS) to detect alleles associated with increased resistance to FER in a set of 818 tropical maize inbred lines evaluated in three environments. Association tests performed using 43,424 single-nucleotide polymorphic (SNPs) markers identified 45 SNPs and 15 haplotypes that were significantly associated with FER resistance. Each associated SNP locus had relatively small additive effects on disease resistance and accounted for 1-4% of trait variation. These SNPs and haplotypes were located within or adjacent to 38 candidate genes, 21 of which were candidate genes associated with plant tolerance to stresses, including disease resistance. Linkage mapping in four biparental populations to validate GWAS results identified 15 quantitative trait loci (QTL) associated with F. verticillioides resistance. Integration of GWAS and QTL to the maize physical map showed eight colocated loci on chromosomes 2, 3, 4, 5, 9, and 10. QTL on chromosomes 2 and 9 are new. These results reveal that FER resistance is a complex trait that is conditioned by multiple genes with minor effects. The value of selection on identified markers for improving FER resistance is limited; rather, selection to combine small effect resistance alleles combined with genomic selection for polygenic background for both the target and general adaptation traits might be fruitful for increasing FER resistance in maize.

Sds22 participates in Glc7 mediated Rad53 dephosphorylation in MMS-induced DNA damage in Candida albicans.

The protein kinase Rad53 and its orthologs play a fundamental role in regulating the DNA damage checkpoint in eukaryotes. Rad53 is activated by phosphorylation in response to DNA damage and deactivated by dephosphorylation after the damage is repaired. However, the phosphatases involved in Rad53 deactivation are not entirely understood. In this study, by investigating the consequences of overexpressing SDS22, a gene encoding a regulatory subunit of the PP1 phosphatase Glc7, in the human fungal pathogen Candida albicans, we discovered that Sds22 plays an important role in Rad53 dephosphorylation and thus the deactivation of the DNA damage checkpoint. Sds22 cellular levels increase when cells are exposed to DNA damaging agents and decrease after removing the genotoxins. Depletion of Glc7 has similar phenotypes. We provide evidence that Sds2 acts through inhibitory physical association with Glc7. Our findings provide novel insights into the mechanisms for the control of DNA damage checkpoint. Furthermore, SDS22 overexpression reduces C. albicans virulence in a mouse model of systemic infection, suggesting potential targets for developing antifungal drugs.

MAE4, an eLtaS monoclonal antibody, blocks Staphylococcus aureus virulence.

Staphylococcus aureus causes a wide range of infectious diseases. Treatment of these infections has become increasingly difficult due to the widespread emergence of antibiotic-resistant strains; therefore, it is essential to explore effective alternatives to antibiotics. A secreted protein of S. aureus, known as eLtaS, is an extracellular protein released from the bacterial membrane protein, LtaS. However, the role of eLtaS in S. aureus pathogenesis remains largely unknown. Here we show eLtaS dramatically aggravates S. aureus infection by binding to C3b and then inhibiting the phagocytosis of C3b-deposited S. aureus. Furthermore, we developed a monoclonal antibody against eLtaS, MAE4, which neutralizes the activity of eLtaS and blocks staphylococcal evasion of phagocytosis. Consequently, MAE4 is capable of protecting mice from lethal S. aureus infection. Our findings reveal that targeting of eLtaS by MAE4 is a potential therapeutic strategy for the treatment of infectious diseases caused by S. aureus.

RNAIII suppresses the expression of LtaS via acting as an antisense RNA in Staphylococcus aureus.

RNAIII is known as the key effector of staphylococcal accessory gene regulator (agr) quorum-sensing system, which plays a central role in the pathogenesis of Staphylococcus aureus. As a regulatory RNA, RNAIII regulates multiple targets, including exoproteins and cell-wall-associated proteins. Lipoteichoic acid synthase (LtaS) is involved in the synthesis of lipoteichoic acid (LTA) that is one of the major components of cell wall. The chemical compound targeting to LtaS decreases S. aureus growth via blocking LTA production. Until now, the regulatory mechanism of LtaS expression is still not clear. The level of ltaS mRNA in S. aureus is analyzed by semi-quantitative RT-PCR analysis and qRT-PCR. The protein level of LtaS is determined by Western blotting. The putative interaction sites between RNAIII and LtaS mRNA are predicted. And LtaS-5ºUTR-lacZ and LtaS-5ºUTR-mutant-lacZ reporter vectors are constructed according to the putative interaction sites. Our data show that the expression of ltaS is regulated by RNAIII in S. aureus. The level of LtaS is significantly higher in the RNAIII deficient strain compared to its parent strain. In the further investigation, 5ºUTR of ltaS was predicted to be the putative interaction site of RNAIII. The results of detection of ß-galactosidase activities suggest that RNAIII can inhibit the expression level of LtaS through acting on the 5ºUTR region of LtaS mRNA. Our finding presents that LtaS is another target of RNAIII and RNAIII suppresses the expression of LtaS via acting as an antisense RNA in S. aureus.