Format: ORAL

Lorenzo F. Manjarrez1, Nuria de Mara1, Mara . Guevara1, Mara D. Vlez1, Jos A. Cabezas1, Jos A. Mancha1, Paula Ramos1, Alberto Pizarro2, Miriam Lpez-Hinojosa1, Irene Cobo-Simn1, Mara C. Daz-Sala2, Mara T. Cervera1

1 Institute of Forest Science - National Institute for Agricultural and Food Research and Technology, Spanish National Research Council (ICIFOR-INIA, CSIC), Madrid, Spain 2 University of Alcalá (UAH), Alcalá de Henares, Spain

Growing body of evidence has stablished miRNAs as a key regulation component of multiple biological processes across diverse species. Yet, studies focusing on miRNAs in forest species, particularly in gymnosperms like conifers, remain scarce. This scarcity limits our comprehension of how forest trees sense and respond to environmental stimuli to manage stress. Pinus pinaster Ait., a native conifer to the western Mediterranean, has held significant ecological and socioeconomic value for decades, emerging as an European model species due to its remarkable genetic variability, which has made it possible for this species to thrive in a wide variety of habitats, ranging from Mediterranean areas to the Atlantic coast. All these features make P. pinaster exceptional for studying the response and adaptation of conifers to water stress. In this study, we explored miRNA profiles from sampled stems of four different graft constructs. These grafts combined four genotypes that showed contrasting response to drought in previous studies. We used Gal1056 (drought-sensitive) and Oria6 (drought-tolerant) as scions grafted onto either R1S (drought-sensitive) or R18T (drought-tolerant) rootstocks. The rootstock genotypes are F1 siblings derived from the controlled cross Gal1056 x Oria6, vegetatively propagated. Three biological replicates of each graft construct were grown under water deficit and control conditions. This study will likely reveal potential roles of some miRNA families regulating transcripts associated with the response and tolerance to water stress. We can envisage they might regulate the expression of genes involved in response to osmotic and oxidative stresses, signalling of growth regulators (abscisic acid or ethylene) and controlling compatible solute metabolism. Additionally, other miRNA families, including two novel families, are involved in regulation of defence response and signal transduction.