ppt presentation：PPT演示.pptVIP

Modulation of RNAi regulation of gene expression in plant development Phenotypic changes caused by knock-out of a MIR gene Phenotypic changes caused by expression of miRNA-resistant variants of target genes (same protein encoded by different nucleotide sequence non-homologous to miRNA) Parental imprinting varying epigenetic modification of alleles inherited from father and mather (parental imprint) – it results in differencial expression of these alleles in zygote = alleles of some genes are methylated in one or the other gamet evolved in mammals and angiospermous plants hemizygote“ state can serve to ensure reasonable feeding of embryo (in mather body) – prevents evolution of paternal alleles causing excessive embryo feeding (in angiosperms – determination of endosperm size) - in plants – main function – repression of TE activity! Parental imprinting Mammals: imprint establishment connected with meiosis - extensive demethylation, specific methylation of some genes Plants: imprint establishes during development of gametophyte (haploid phase in plants: (polen) polen tube + embryo sac) demethylation in a part of gametophyte – genetically terminal lines - central cell of embryo sac (DME - DEMETER) - vegetative nucleus of polen tube (block of DDM1, DME) Epigenetic changes in microgametophyte Primary function: induction of proper TE methylation in generative cells (sperm cells): Demethylation – reactivation of TE – siRNA formation – transport to spermatic cells – induction of proper TE methylation Inhibition of methylation (repression DDM1) + actively (DME) In vegetative nucleus Primary function: - block of TE and endosperm specific genes in egg cell regulation of endosperm size block of gametophytic developmental program? Epigenetic changes in megagametophyte - repression state kept primarily by di-(tri-)methylation of histon H3K27 - in vegetative Arabidopsis tissue – thousands genes! - Maintenance of H3K27me2 mediated by gen