Rootstock effects on scion gene expression in maritime pine
Pines are the dominant conifers in Mediterranean forests. As long-lived sessile organisms that seasonally have to cope with drought periods, they have developed a variety of adaptive responses. However, during last decades, highly intense and long-lasting drought events could have contributed to decay and mortality of the most susceptible trees. Among conifer species, Pinus pinaster Ait. shows remarkable ability to adapt to different environments. Previous molecular analysis of a full-sib family designed to study drought response led us to find active transcriptional activity of stress-responding genes even without water deprivation in tolerant genotypes. To improve our knowledge about communication between above- and below-ground organs of maritime pine, we have analyzed four graft-type constructions using two siblings as rootstocks and their progenitors, Gal 1056 and Oria 6, as scions. Transcriptomic profiles of needles from both scions were modified by the rootstock they were grafted on. However, the most significant differential gene expression was observed in drought-sensitive Gal 1056, while in drought-tolerant Oria 6, differential gene expression was very much lower. Furthermore, both scions grafted onto drought-tolerant rootstocks showed activation of genes involved in tolerance to abiotic stress, and is most remarkable in Oria 6 grafts where higher accumulation of transcripts involved in phytohormone action, transcriptional regulation, photosynthesis and signaling has been found. Additionally, processes, such as those related to secondary metabolism, were mainly associated with the scion genotype. This study provides pioneering information about rootstock effects on scion gene expression in conifers. ; Cruz Anegón Esteban and Enrique Sastre-Callejo from Área de Recursos Genéticos Forestales (MITECO) are gratefully acknowledge for grafting the pine trees. Daniel Carrillo Bautista and Juan Gallego Zamorano from ADM and Radboud University, respectively, are gratefully acknowledged for their advice in the bioinformatics analyses. Susana Ferrándiz (INIA-CIFOR) is gratefully acknowledged for helping with the preparation of the manuscript. This work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (AGL2015-66048-C2-1-R; RTI2018-098015-B-I00), and by University of Alcalá (UAH-AE 2017-2). Segregating progeny was obtained in accordance with the national ABS legislation before the Nagoya Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from their Utilization to the Convention on Biological Diversity was legally implemented by signatory countries. ; Peer reviewed
