| Abstract | U biljaka (kao i ostalih eukariota) postoji velika raznolikost molekula RNA. One imaju
esencijalne i posebne uloge u stanici i organizmu. Uz kodirajuće mRNA važnu ulogu u ekspresiji
gena imaju i ncRNA, u koje se ubrajaju tRNA, rRNA, lncRNA, snRNA, snoRNA, miRNA, siRNA
i druge sRNA. Tema su ovog rada male molekule RNA, sRNA, čiji su najbolje istraženi
predstavnici upravo neke ncRNA: snRNA, snoRNA, miRNA i siRNA. miRNA i siRNA sudjeluju
u putevima RNA utišavanja, odnosno smanjuju razinu ekspresije ciljanih gena u različitim
uvjetima. U biljaka se utišavanje obično provodi na posttranskripcijskoj razini putem cijepanja
mRNA ciljanog gena. Za aktivnost ovih sRNA potrebni su određeni proteini, prvenstveno DCL
enzimi, koji cijepaju njihove prekursore, te Argonauti, koji su glavna komponenta kompleksa
RISC i cijepaju ciljane komplementarne molekule mRNA. hcsiRNA imaju posebnu ulogu u
regulaciji ekspresije gena na transkripcijskoj razini, gdje se metilacijom DNA usmjerenom
molekulom RNA utišavaju ciljani geni (epigenetska regulacija). Osim regulacije ekspresije
endogenih gena, siRNA i RNAi pružaju biljkama važan način obrane od patogena, prvenstveno
od virusa, bakterija i gljiva. U interakciji biljaka i njihovih patogena prisutni su i odgovori patogena
na biljne obrambene mehanizme. I jedni i drugi mehanizmi mijenjaju se i razvijaju tijekom
vremena. Otkrića iz područja RNA utišavanja našla su primjenu u razvijanju različitih metoda koje
se koriste za oplemenjivanje biljaka. |
| Abstract (english) | Plants (just like other eukaryotes) have great diversity of RNA molecules that have
essential and specific functions in cell and organism. Alongside coding mRNAs important function
in gene expression have ncRNAs too, which include tRNAs, rRNAs, lncRNAs, snRNAs,
snoRNAs, miRNAs, siRNAs and other sRNAs. Main topic of this paper are small RNAs (sRNAs),
whose best investigated representatives are some ncRNAs: snRNAs, snoRNAs, miRNAs and
siRNAs. miRNAs and siRNAs act in RNA silencing pathways, i. e. they reduce expression level
of targeted genes in different conditions. In plants, silencing is usually executed on
posttranscriptional level by targeted gene mRNA degrading. For activity of these sRNAs are
required some proteins, in first place DCL enzymes, which cleave their precursors, and Argonaute
enzymes, which are principal component of RISC complex and they degrade targeted
complementary mRNAs. hcsiRNAs have specific role in regulation of gene expression on
transcriptional level: targeted genes are silenced by RNA-directed DNA methylation (epigenetic
regulation). Beside endogenous genes expression regulation, siRNAs and RNAi provide important
defense mechanisms that protect plants from pathogens, especially from viruses, bacteria and
fungi. In interaction of plants and their pathogens, pathogen responses on plant defense
mechanisms are also present, both are changing and developing through time. Discoveries in the
field of RNA silencing found application in developing of different methods for agricultural plant
breeding |
