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1、MYB transcription factors in plantsMore than 20 years ago,the first gene encoding a transcription factor in plants was identified COLORED1(C1)A decade ago,the Arabidopsis genome sequence was published,which provided the first comprehensive description and classification of plant MYB genes.In rencent
2、 years,the functions of MYB proteins have been investigated in numerous plant species.第1页/共20页第一页，编辑于星期六：九点 五十一分。Structure and evolutionMYB proteins are characterized by a highly conserved DNA-binding domain:the MYB domain（consists of up to four imperfect amino acid sequence repeats(R)of about 52 am
3、ino acids,each forming three ahelices).MYB proteins can be divided into different classes depending on the number of adjacent repeats(one,two,three or four)第2页/共20页第二页，编辑于星期六：九点 五十一分。第3页/共20页第三页，编辑于星期六：九点 五十一分。In contrast to the highly conserved MYB domain,the other regions of R2R3-MYB proteins are
4、highly variable.Based on the conservation of the DNAbinding domain and of amino acid motifs in the C terminal domains,R2R3-MYB proteins have been divided into subgroups.第4页/共20页第四页，编辑于星期六：九点 五十一分。第5页/共20页第五页，编辑于星期六：九点 五十一分。Diversity of functionsNumerous R2R3-MYB proteins have been characterized by g
5、enetic approaches and found to be involved in the control of plant-specific processes including:(i)primary and secondary metabolism(ii)cell fate and identity(iii)developmental processes(iv)responses to biotic and abiotic stresses第6页/共20页第六页，编辑于星期六：九点 五十一分。第7页/共20页第七页，编辑于星期六：九点 五十一分。Regulation of MYB
6、 functionsMYB genes are targets to both microRNAs(miRNAs)and transacting,silencing RNAs(ta-siRNAs).Post-translational modifications and proteinprotein interactions can significantly impact the regulatory activity of MYB transcription factors.The transcriptional activity of some R2R3-MYB factors is d
7、ependent in vivo on proteinprotein interactions.Phosphorylation is important in determining MYB protein activity.第8页/共20页第八页，编辑于星期六：九点 五十一分。Redox control is thought to influence MYB protein activity because of the presence of a pair of conserved Cys residues,four residues apart,in the R2-MYB motif o
8、f most 3R-and R2R3-MYB proteinsThe activity of many transcriptional regulators is modulated by conjugation with ubiquitin or the small ubiquitinrelated modifierThe modulation of transcription factor activity by sumoylation can occur by multiple mechanisms including subcellular localization,DNA-bindi
9、ng activity or decreasing the activity of a TAD,as described for animal c-Myb第9页/共20页第九页，编辑于星期六：九点 五十一分。MYB proteins in regulatory networksMYB transcription factors have been identified as immediate targets of other regulators.Eg.AGL15,a member of the MADS family involved in embryo development,which
10、 directly binds to 29 different MYB genes from a total of 2000 target genes,although binding to DNA is not always synonymous with transcriptional regulation.Other MYB factors for which direct targets have been identified seem to target primarily non-transcription factor genes.第10页/共20页第十页，编辑于星期六：九点
11、五十一分。A Myb transcription factor regulates genes of thephenylalanine pathway in maritime pine第11页/共20页第十一页，编辑于星期六：九点 五十一分。Trees,including conifers,divert large quantities of carbon into the biosynthesis of phenylpropanoids,particularly to generate lignin,an important constituent of wood.(Wagner et al
12、.,2012).Lignin biosynthesis is one of the most energy demanding biosynthetic pathways in plants(Amthor,2003).Although lignin and other phenolic compounds do not contain nitrogen,phenylalanine metabolism is required to channel photosynthesis-derived carbon to phenylpropanoid biosynthesis.第12页/共20页第十二
13、页，编辑于星期六：九点 五十一分。第13页/共20页第十三页，编辑于星期六：九点 五十一分。Isolation of maritime pine GS1b,PAL and PAT promoters.In silico analysis of putative cis elements第14页/共20页第十四页，编辑于星期六：九点 五十一分。R2R3Myb proteins bind to the PAL,PpGS1b and PAT AC-II boxesAn in vitro analysis of proteinDNA interactions using an electrophore
14、tic mobility shift assay(EMSA).The EMSA analysis showed noticeable differences in the intensity of shifts,depending on the boxes and Myb proteins used.第15页/共20页第十五页，编辑于星期六：九点 五十一分。第16页/共20页第十六页，编辑于星期六：九点 五十一分。Expression analysis of the PAL,GS1b,PAT,Myb1,Myb4 and Myb8 genes in maritime pine第17页/共20页第十七页，编辑于星期六：九点 五十一分。Role of the conserved AC-II element in the PAL,GS1b and PAT promoters第18页/共20页第十八页，编辑于星期六：九点 五十一分。Thank you for your attantion!第19页/共20页第十九页，编辑于星期六：九点 五十一分。感谢您的观看！第20页/共20页第二十页，编辑于星期六：九点 五十一分。