BoMyrosinase plays an essential role in sulforaphane accumulation in response to selenite treatment in broccoli

Sulforaphane, a naturally specialized metabolite, plays significant roles in human disease prevention and plant defense. Myrosinase(MY) is a key gene responsible for the catalysis of sulforaphane formation, but the molecular mechanisms through which MY regulates sulforaphane biosynthesis in plants remains largely unknown. Here, we discovered that the change of sulforaphane content in broccoli sprouts caused by exogenous selenite treatments is positively related to BoMY expression. BoMY overexpression in the Arabidopsis thaliana tgg1 mutants could dramatically increase myrosinase activity and sulforaphane content in the rosette leaves of 35S::BoMY/tgg1 and rescue its phenotypes.Moreover, an obvious increase of myrosinase activity and sulforaphane content was displayed in transgenic BoMY-overexpressed broccoli lines.In addition, a 2 033 bp promoter fragment of BoMY was isolated. Yeast one-hybrid(Y1H) library screening experiment uncovered that one bHLH transcription factor, BoFAMA, could directly bind to BoMY promoter to activate its expression, which was further evidenced by Y1H assay and dual-luciferase reporter assay. BoFAMA is a selenite-responsive transcription factor that is highly expressed in broccoli leaves;its protein is solely localized to nucleus. Additionally, genetic evidence suggested that the knockdown of FAMA gene in Arabidopsis thaliana could significantly decrease sulforaphane yield by inhibiting the expression of myrosinase genes. Interestingly, exogenous selenite supply could partially restore the low level of sulforaphane content in transgenic Arabidopsis FAMA-silencing plants. Our findings uncover a novel function of FAMAMY module in the regulation of selenite-mediated sulforaphane synthesis and provide a new insights into the molecular mechanism by which selenite regulates the accumulation of sulforaphane in plants.

A global view of transcriptome dynamics during flower development in Capsicum annuum L.

An analysis of genome-wide gene expression profiles during floral organ development can provide important clues about the molecular basis of gene functions and developmental processes.In this study,we analyzed the transcriptome data of 36 samples obtained during floral organ development from pepper‘6421’and detected 30016 genes that were expressed in at least one sample.K-means clustering analysis was used to classify the data into 16 clusters based on the similarities between the dynamic expression profiles of genes.Of these,15 clusters exhibited notable up-regulation or down-regulation trends in different developmental stages or tissues of floral organs.We identified transcription factors expressed at the early,medium,and late stages of bud development(F1,F5,F9).Transcription factor families such as AP2-ERF,MADS-box,MYB,bHLH,and NAC showed significant levels of enrichment.In comparison with genes expressed in vegetative tissues at different stages,certain genes were specifically up-regulated during flower development;among these,the number of genes specifically up-regulated during the stamen(Sta10)and bud tetrad development(F4)stages was the highest.Through extensive studies of the ABCDE model of flower development in Arabidopsis,we identified 17 ABCDE model candidate genes in pepper,most of which were up-regulated at specific stages of flower bud development.The expression data provided in this study is the most comprehensive dataset available for pepper to date and will serve as a resource for identifying the functions of many specific genes involved in flower development in pepper and other Solanaceae plants.

A multi-omics approach identifies bHLH71-like as a positive regulator of yellowing leaf pepper mutants exposed to high-intensity light

Light quality and intensity can have a significant impact on plant health and crop productivity.Chlorophylls and carotenoids are classes of plant pigments that are responsible for harvesting light energy and protecting plants from the damaging effects of intense light.Our understanding of the role played by plant pigments in light sensitivity has been aided by light-sensitive mutants that change colors upon exposure to light of variable intensity.In this study,we conducted transcriptomic,metabolomic,and hormone analyses on a novel yellowing mutant of pepper(yl1)to shed light on the molecular mechanism that regulates the transition from green to yellow leaves in this mutant upon exposure to high-intensity light.Our results revealed greater accumulation of the carotenoid precursor phytoene and the carotenoids phytofluene,antheraxanthin,and zeaxanthin in yl1 compared with wild-type plants under high light intensity.A transcriptomic analysis confirmed that enzymes involved in zeaxanthin and antheraxanthin biosynthesis were upregulated in yl1 upon exposure to high-intensity light.We also identified a single basic helix–loop–helix(bHLH)transcription factor,bHLH71-like,that was differentially expressed and positively correlated with light intensity in yl1.Silencing of bHLH71-like in pepper plants suppressed the yellowing phenotype and led to reduced accumulation of zeaxanthin and antheraxanthin.We propose that the yellow phenotype of yl1 induced by high light intensity could be caused by an increase in yellow carotenoid pigments,concurrent with a decrease in chlorophyll accumulation.Our results also suggest that bHLH71-like functions as a positive regulator of carotenoid biosynthesis in pepper.

Selenocysteine methyltransferase SMT catalyzed the synthesis of Se-methylselenocysteine to regulate the accumulation of glucosinolates and sulforaphane in broccoli

Selenocysteine methyltransferase(SMT)is a key enzyme involved in the Se metabolism pathway,and it is responsible for the catalysis of Se-methylselenocysteine(SeMSC)compound formation.Previous studies showed that selenium treatment activated SMT expression and promoted the accumulation of glucosinolates(GSLs)and sulforaphane,but the roles and functional mechanisms of SMT in mediating GSLs and sulforaphane synthesis remain unclear.In this study,we identified the BoSMT gene in broccoli and uncovered its roles in mediating GSLs biosynthesis.Transgenic assays revealed that BoSMT is involved in SeMSC biosynthesis in broccoli.More importantly,the contents of GSLs and sulforaphane were significantly increased in the BoSMT-overexpressing broccoli lines but decreased in the knockdown lines,suggesting that BoSMT played a positive role in regulating GSLs and sulforaphane synthesis.Further evidence indicated that BoSMT-mediated overaccumulation of GSLs and sulforaphane might be due to the increase in the endogenous SeMSC content.Compared with the mock(water)treatment,selenite-induced significantly increases of the SeMSC content in the BoSMT-knockdown plants partially compensated the phenotype of GSLs and sulforaphane loss.Compared with the mock treatment,exogenous SeMSC treatment significantly increased the contents of GSL and sulforaphane and activated GSL synthesis-related gene expression,suggesting that SeMSC acted as a positive regulator for GSL and sulforaphane production.Our findings provided novel insights into selenium-mediated GSLs and sulforaphane accumulation.The genetic manipulation of BoSMT might be a useful strategy for improving the dietary nutritional values of broccoli.

Exogenously applied methyl Jasmonate induces early defense related genes in response to Phytophthora infestans infection in potato plants

In order to elucidate the contributions of JA in orchestrating disease resistance in potato plants,the potato genotype‘SD20’,which exhibits strong resistance against the highly virulent Phytophthora infestans isolate CN152,while infected by the super virulent isolate 2013-18-306,was treated with exogenous JA and then challenged by inoculation with 2013-18-306.The results showed that exogenously applied JA significantly delayed the onset and alleviated the symptoms of late blight,indicating exogenous JA could induce resistance to P.infestans in the early biotrophic stage of infection in‘SD20’plants.To further clarify the role of JA in the early defense response and identify key genes involved in JA signal transduction,gene expression profiling via RNA sequencing(RNA-seq)in‘SD20’plants treated with exogenously applied JA was performed.A total of 2927 differentially expressed genes were specifically induced,the majority encoded transcription factors,protein kinases,secondary metabolites,defense enzymes and disease resistance related proteins.GO functional annotation and KEGG metabolic pathway analysis showed that exogenously applied JA rapidly induced the expression of genes related to immune response regulation,pathogen defense,and other biological processes,and stimulated endogenous JA synthesis and signal transduction,and the overall early pathogen defense response in‘SD20’.These results provide useful information in understanding the JA’s function involved in pathogen defense responses and a theoretical basis for the application of JA in potato production.