Myb轉(zhuǎn)錄因子PPT課件

1、 MYB transcription factors in plants More 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

2、rencent years,the functions of MYB proteins have been investigated in numerous plant species.第1頁/共20頁 Structure and evolution MYB 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 amino ac

3、ids, 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頁/共20頁第3頁/共20頁 In contrast to the highly conserved MYB domain, the other regions of R2R3-MYB proteins are highly variable. Based on the conservat

4、ion of the DNAbinding domain and of amino acid motifs in the C terminal domains, R2R3-MYB proteins have been divided into subgroups.第4頁/共20頁第5頁/共20頁 Diversity of functions Numerous R2R3-MYB proteins have been characterized by genetic approaches and found to be involved in the control of plant-specif

5、ic processes including: (i) primary and secondary metabolism (ii) cell fate and identity (iii) developmental processes (iv) responses to biotic and abiotic stresses第6頁/共20頁第7頁/共20頁 Regulation of MYB functions MYB genes are targets to both microRNAs (miRNAs) and transacting, silencing RNAs (ta-siRNAs

6、). 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 dependent in vivo on proteinprotein interactions. Phosphorylation is important in determining MY

7、B protein activity.第8頁/共20頁 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 of most 3R- and R2R3-MYB proteins The activity of many transcriptional regulators is modulated by conjugation w

8、ith ubiquitin or the small ubiquitinrelated modifier The modulation of transcription factor activity by sumoylation can occur by multiple mechanisms including subcellular localization, DNA-binding activity or decreasing the activity of a TAD, as described for animal c-Myb第9頁/共20頁 MYB proteins in reg

9、ulatory networks MYB transcription factors have been identified as immediate targets of other regulators. Eg. AGL15, a member of the MADS family involved in embryo development, which directly binds to 29 different MYB genes from a total of 2000 target genes, although binding to DNA is not always syn

10、onymous with transcriptional regulation. Other MYB factors for which direct targets have been identified seem to target primarily non-transcription factor genes.第10頁/共20頁A Myb transcription factor regulates genes of thephenylalanine pathway in maritime pine第11頁/共20頁 Trees, including conifers, divert

11、 large quantities of carbon into the biosynthesis of phenylpropanoids, particularly to generate lignin, an important constituent of wood.(Wagner et al., 2012). Lignin biosynthesis is one of the most energy demanding biosynthetic pathways in plants(Amthor,2003). Although lignin and other phenolic com

12、pounds do not contain nitrogen, phenylalanine metabolism is required to channel photosynthesis-derived carbon to phenylpropanoid biosynthesis.第12頁/共20頁第13頁/共20頁 Isolation of maritime pine GS1b, PAL and PAT promoters.In silico analysis of putative cis elements第14頁/共20頁 R2R3Myb proteins bind to the PAL, PpGS1b and PAT AC-II boxes An in vitro analysis of proteinDNA interactions using an electrophoretic 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頁/共20頁第16頁/共20頁 Expression analysis of