MicroRNA-induced regulation of wheat (Triticum aestivum L.) root architecture and function

Giorgia Tonielli ¹, Alessia D’Agostino ², Gabriele Di Marco ², Gerardo Pepe ², Adelaide Teofani ², Chiara Pontecorvi ², Manuela Helmer Citterich ², Antonella Canini ², Angelo Gismondi ²

1Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma, Italy 2 PhD program in Cellular and Molecular Biology, University of Rome Tor Vergata ¹, 1 ²

Wheat (Triticum sp.) is one of the most cultivated crops in the world, providing about 20% of the total calories in the human diet. Unfortunately, in the next decade, the increasing worldwide food demand and the present climate change issues have made insufficient the current grain yield rate. In recent years, the attention of scholars has been focused on promoting the root system architecture (RSA) of this species to improve its access to nutrients and productivity. However, to date, no study has investigated the role of miRNAs in the regulation of Triticum aestivum RSA. Thus, the aim of the present contribution was to investigate the cellular and molecular processes mediated by miRNAs which may determine the root growth in wheat seedlings (Altamira variety), to reach a better comprehension of the phenomena linked to the developmental biology of this species and to favour the design of novel biotechnological approaches able to promote its yield and quality. An initial transcriptomic approach was applied on roots from wheat seedlings grown at different timings (4 and 8 days after seeding, henceforth DAS). The bioinformatic analysis revealed a modulation at these stages of some molecular pathways already known in the literature and associated to RSA (e.g., calcium ion transport and homeostasis, cell wall structure, defense and pathogen response, redox balance). Interestingly, the results also evidenced an upregulation of genes involved in abscisic acid production. To have a better overview on the expression of miRNAs during wheat root growth, a miRNome differential expression analysis was carried out at the same DAS. The results of this analysis revealed the potential modulation of different pathways mediated by microRNAs associated with RSA (e.g. calcium ion transport, cell wall macromolecule catabolic processes, defense response), confirming the evidence obtained by transcriptomics. These findings directed our attention to two specific microRNAs, miR398 and miR397b-5p, which have not yet been studied in wheat root development. Their respective targets—Cu/Zn SOD (Cu, Zn Superoxide Dismutase, involved in detoxifying superoxide anions) and Laccase 2 (a multi-domain cupredoxin oxidoreductase involved in lignification and secondary cell wall biosynthesis)—are known to be regulated by distinct transcription factors activated by ABA. The expression analysis of miR397b-5p and miR398 and their targets in wheat roots at different growth stages (i.e., 4, 6, 8, 10 and 12 DAS) revealed a down regulation of both miRNAs during the root development, while the level of transcript for Laccase 2 remained stable and that of Cu/Zn SOD accumulated. These data would suggest a different regulatory mechanism for the two miRNAs on their respective targets (i.e., inhibition of translation and degradation of the mRNAs). To better define this context, spectrophotometric activity assays were performed for both these enzymes, confirming the putative key function of the two investigated miRNAs on their targets. Lastly, to provide a more general overview of this kind of regulation the transcript level of other Laccases and antioxidant enzymes was monitored. All this preliminary evidence opens new perspectives on the role of the miRNAs in wheat RSA.

Main author career stage: PhD student

Contribution type: Poster

First choice session: 4. Structure, physiology, and development

Second choice session: 4. Structure, physiology, and development