Rootstock effects on scion gene expression in maritime pine

M López-Hinojosa,L M Díaz,L F Manjarrez,A Pizarro,J A Mancha,M A Guevara,M T Cervera Goy,M D Vélez,N De María,C Díaz-Sala,C Collada,J A Cabezas

doi:10.1038/s41598-021-90672-y

Abstract

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.

Highlights

Pines are the dominant conifers in Mediterranean forests
This study reveals processes, such as those associated to secondary metabolism, that are mainly determined by the scion genotype, as well as widespread effect of rootstocks on scion gene expression in Pinus pinaster (Fig. 8)
The different rootstocks significantly affected the transcript profile of Gal 1056, the drought-sensitive scion, especially the expression of genes involved in secondary metabolism, response to external stimuli, phytohormone action and RNA biosynthesis

Summary

Introduction

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. Pinus pinaster shows increased recalcitrance to vegetative propagation by cuttings during the first five years For this reason, maritime pine seed orchards are based on intraspecific grafts of selected trees as scions onto uncontrolled r ootstocks[28]. Maritime pine seed orchards are based on intraspecific grafts of selected trees as scions onto uncontrolled r ootstocks[28] This asexual propagation method, based in the combination of two genotypes, is an ancient agronomic technique that has been routinely used to enhance tolerance to stress, improve quality and increase production of woody and non-woody species[29,30]. In this study we designed intraspecific grafts of P. pinaster using as scions and rootstocks both drought-tolerant and droughtsensitive maritime pine genotypes, to analyze the effect of rootstocks on the needle transcriptome of the scions

Methods

Results

Discussion

Conclusion