5´→ 3´ exoribonucleases participate on iron homeostasis in Arabidopsis thaliana

ESTAVILLO, GONZALO; GOMEZ CASATI, DIEGO; PAGANI M AYELEN; BALPARDA, MANUEL

Rosario

Simposio; Genómica Funcional de Plantas; 2017

Cellular responses to environmental stresses involve changes in RNA transcript levels through the modulation of the kinetics of transcription and decay rates of individual mRNA molecules. The most novel finding is the process of co-transcriptional imprinting of mRNAs with proteins, which in turn regulate cytoplasmic mRNA stability. The XRN family of 5′ → 3′ exoribonucleases is critical for ensuring the fidelity of cellular RNA turnover in eukaryotes. Highly conserved across species, the family is typically represented by one cytoplasmic enzyme (AtXRN4 in Arabidopsis) and one or more nuclear enzymes (AtXRN2 and AtXRN3 in Arabidopsis). XRNs degrade diverse RNA substrates during general RNA decay and function in specialized processes integral to RNA metabolism, such as nonsense-mediated decay (NMD), gene silencing, rRNA maturation, and transcription termination. The Arabidopsis system has been the source of most information about plant XRNs and their roles in small RNA-associated RNA decay mechanisms.3´-phosphoadenisine-5´-phosphate (PAP) inhibits the action of the XRNs which participate in post-transcriptional gene expression regulation. Transcriptomic analysis of Arabidopsis mutant plants in the PAP-SAL1 pathway and in exoribonucleases (sal1, xrn4, xrn2/xrn3) revealed that the ferritin genes AtFer1, AtFer3, and AtFer4 are up-regulated in these genetic backgrounds, thus establishing a link between the PAP retrograde signaling pathway and mRNA decay with the regulation of Fe homeostasis genes. We have further characterized Fe metabolism in these mutants, finding that genes implicated in Fe uptake and storage, and Fe-S cluster biosynthesis are up-regulated, and that iron contents are elevated in both roots and shoots of these lines.