RT Conference Proceedings T1 Involvement of miRNAs in the short-term response of pine roots to ammonium nutrition A1 Ortigosa Peña, Francisco A1 Lobato-Fernández, César A1 Valderrama-Martín, José Miguel A1 Urbano-Gámez, Jose Alberto A1 Cantón, Francisco R. A1 Cañas-Pendón, Rafael Antonio K1 Pinos - Raíces AB Post-transcriptonal gene regulation is an essential control point regarding gene expression programs. A class of small non-coding RNAs, microRNAs (miRNAs) play important roles during this process. They act on target mRNAs through post-transcriptional gene silencing, either by endonuclease mediated transcript cleavage or by translational repression of targeted mRNAs (Pattanayak et al., 2013). Thus, miRNAs are involved in the regulation mechanisms of important plant processes, including the regulation of the processes related to nitrogen nutrition (Gutiérrez, 2012). In the present work, maritime pine (Pinus pinaster Aiton) was used to study the role of miRNAs regarding NH4+ nutrition in conifers, a group of plants that exhibits tolerance to NH4+ nutrition compared to NO3- nutrition specially during seedling stage Ortigosa et al., 2022). This fact is of high interest since numerous NH4+ nutrition can negatively affect the growth and development of different crops.The global miRNA expression has been characterized in the roots of maritime pine seedlings after 2 h and 24 h from fertilization with two levels of NH4+ solutions (0.1 mM and 3 mM). The miRNA-seq analysis revealed 271 new miRNAs with an identified precursor although only 4 were differentially expressed.Gutiérrez RA. 2012. Science, 336:1673-1675.Ortigosa F, et al. 2022. Plant Cell and Environment, 45,915-935.Pattanayak D, et al. 2013. Plant Molecular Biology Reporter, 31, 493-506. YR 2022 FD 2022 LK https://hdl.handle.net/10630/25059 UL https://hdl.handle.net/10630/25059 LA eng NO Acknowledgements & Funding. This work was supported by the grants BIO2015-73512-JIN MINECO/AEI/FEDER, UE; P20_00036 PAIDI 2020/FEDER, UE, and B4-2021-01 (Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech). JMVM was supported by the grant FPU17/03517. DS RIUMA. Repositorio Institucional de la Universidad de Málaga RD 21 ene 2026