Contrasting transcriptomic patterns reveal a genomic basis for drought resilience in the relict fir Abies pinsapo Boiss

Abstract

Climate change challenges the adaptive capacity of several forest tree species in the face of increasing drought and rising temperatures. Therefore, understanding the mechanistic connections between genetic diversity and drought resilience is highly valuable for conserving drought-sensitive forests. Nonetheless, the post-drought recovery in trees from a transcriptomic perspective has not yet been studied by comparing contrasting phenotypes. Here, experimental drought treatments, gas-exchange dynamics, and transcriptomic analysis (RNA-seq) were performed in the relict and drought-sensitive fir Abies pinsapo to identify gene expression differences over immediate (24 hours) and extended drought (20 days). Post-drought responses were investigated to define resilient and sensitive phenotypes. Single nucleotide polymorphisms (SNPs) were also studied to characterize the genomic basis of A. pinsapo drought resilience. Weighted gene co-expression network analysis showed an activation of stomatal closing and an inhibition of plant growth-related genes during the immediate drought, consistent with an isohydric dynamic. During the extended drought, transcription factors, as well as cellular damage and homeostasis protection-related genes prevailed. Resilient individuals activate photosynthesis-related genes and inhibit aerial growth-related genes, suggesting a shifting shoot/root biomass allocation to improve water uptake and whole-plant carbon balance. 152 fixed SNPs were found between resilient and sensitive seedlings, which were mostly located in RNA-activity-related genes, including epigenetic regulation. Contrasting gene expression and SNPs were found between different post-drought resilience phenotypes for the first time in a forest tree, suggesting a transcriptomic and genomic basis for drought resilience. The obtained drought-related transcriptomic profile and drought-resilience candidate genes may guide conservation programs for this threatened tree species.

De novo transcriptome sequencing and gene co-expression reveal a genomic basis for drought sensitivity and evidence of a rapid local adaptation on Atlas cedar (Cedrus atlantica)

“…This isohydric pattern has been observed in this work in C. atlantica seedlings through a progressive decrease of A and Gs values in both populations (Figure 3). These findings are similar to those obtained in A. pinsapo seedlings using the same study design (Cobo-Simoń et al, 2022), whose physiological response to drought is also isohydric.…”

“…Our findings, especially when complemented with those from A. pinsapo (Cobo-Simoń et al, 2022), shed light on the adaptive potential of trees in general, and relict conifers in particular, to the projected increasing drought caused by current climate change, which is particularly concerning in Mediterranean and other semiarid climates. This information will allow us better predict their future perspectives facing current global warming.…”

“…All these functions are related to plant response during drought stress (Kahur et al. 202, Tenhaken, 2015 ; Chen et al., 2021 ; Cobo-Simón et al., 2022 , see DroughtDB Alter 2015, see Discussion). Among the down-regulated, the more prevalent GO terms were related to DNA/RNA biosynthesis and regulation, cell wall organization and anatomical structure development ( Figure 9D ), related to aerial plant growth inhibition, which can be observed during drought stress response in plants ( Miao et al., 2017 ).…”

“…In particular, stomatal movement, potassium ion import, regulation of membrane potential, cell wall reorganization, sugar metabolism, cellular response to DNA damage stimulus, and protein ubiquitination GO terms were found among the up-regulated genes (Figure 9C). All these functions are related to plant response during drought stress (Kahur et al 202, Tenhaken, 2015;Chen et al, 2021;Cobo-Simoń et al, 2022, see DroughtDB Alter 2015, see Discussion). Among the down-regulated, the more prevalent GO terms were related to DNA/RNA biosynthesis and regulation, cell wall organization and anatomical structure development (Figure 9D), related to aerial plant growth inhibition, which can be observed during drought stress response in plants (Miao et al, 2017).…”

“…Relicts usually have small population sizes, isolation and limited possibilities for migration, leading to reduced gene flow and genetic diversity, which make them unique experimental models to test the adaptive potential of trees to a changing environment ( Hampe and Petit, 2005 ; e.g. Cobo-Simón et al., 2020 ; Cobo-Simón et al., 2021 ; Cobo-Simón et al., 2022 ). Despite this, some studies have found no evidence of decreasing population sizes or fitness ( Hampe and Jump, 2011 ).…”