Exorribonucleases participate on iron homeostasis in Arabidopsis thaliana.

BALPARDA, M.; PAGANI, M.A.; ESTAVILLO, G.; DIEGO FABIAN GOMEZ CASATI

Rosario

Simposio; Simposio de Genómica Funcional de Plantas; 2017

Cellularresponses to environmental stresses involve changes in RNA transcript levelsthrough the modulation of the kinetics of transcription and decay rates ofindividual mRNA molecules. The most novel finding is the process ofco-transcriptional imprinting of mRNAs with proteins, which in turn regulatecytoplasmic mRNA stability.The XRN family of 5′ → 3′ exoribonucleasesis critical for ensuring the fidelity of cellular RNA turnoverin eukaryotes. Highly conserved across species, the family is typically representedby one cytoplasmic enzyme (AtXRN4 in Arabidopsis) and one or more nuclearenzymes (AtXRN2 and AtXRN3 in Arabidopsis). XRNs degrade diverse RNA substrates during generalRNA decay and function in specialized processes integral to RNA metabolism, suchas nonsense-mediated decay (NMD), gene silencing, rRNA maturation, andtranscription termination. The Arabidopsissystem has been the source of most information about plant XRNs and their rolesin small RNA-associated RNA decay mechanisms.3´-phosphoadenisine-5´-phosphate(PAP) inhibits the action of the XRNs which participate in post-transcriptionalgene expression regulation. Transcriptomic analysis of Arabidopsis mutant plants in the PAP-SAL1 pathway and inexoribonucleases(sal1, xrn4, xrn2/xrn3)revealed that the ferritin genes AtFer1,AtFer3, and AtFer4 are up-regulated in these genetic backgrounds, thusestablishing a link between the PAP retrograde signaling pathway andmRNA decaywiththeregulation of Fe homeostasis genes. We have further characterized Fe metabolismin these mutants, finding that genes implicated in Fe uptake and storage, andFe-S cluster biosynthesis are up-regulated, and that iron contents are elevatedin both roots and shoots of these lines.