High-density genetic map and identification of QTLs for responses to temperature and salinity stresses in the model brown alga Ectocarpus

Abstract

Deciphering the genetic architecture of adaptation of brown algae to environmental stresses such as temperature and salinity is of evolutionary as well as of practical interest. The filamentous brown alga Ectocarpus sp. is a model for the brown algae and its genome has been sequenced. As sessile organisms, brown algae need to be capable of resisting the various abiotic stressors that act in the intertidal zone (e.g. osmotic pressure, temperature, salinity, UV radiation) and previous studies have shown that an important proportion of the expressed genes is regulated in response to hyposaline, hypersaline or oxidative stress conditions. Using the double digest RAD sequencing method, we constructed a dense genetic map with 3,588 SNP markers and identified 39 QTLs for growth-related traits and their plasticity under different temperature and salinity conditions (tolerance to high temperature and low salinity). GO enrichment tests within QTL intervals highlighted membrane transport processes such as ion transporters. Our study represents a significant step towards deciphering the genetic basis of adaptation of Ectocarpus sp. to stress conditions and provides a substantial resource to the increasing list of tools generated for the species.

DISTAG/TBCCd1 Is Required for Basal Cell Fate Determination in Ectocarpus

“…Recently, the filamentous alga Ectocarpus sp has emerged as a genetic model for the brown algae (Coelho et al, 2012c;Cock et al, 2014). A high-quality genome sequence is available for this species Cormier et al, 2017), together with extensive transcriptomic data Luthringer et al, 2015) and genetic tools including a dense genetic map (Heesch et al, 2010;Avia et al, 2017). Genetic transformation is not yet possible, but gene knockdown using RNA interference has been demonstrated (Macaisne et al, 2017).…”

The antagonistic effect of UV radiation on warming or nitrate enrichment depends on ecotypes of freshwater macroalgae (Charophytes)

“…We encourage studies that genetically test the relative impacts of local adaptation to specific environments, and an increase in phenotypic plasticity in charophytes governed by stressor interactions as is occurring in marine macroalgae (Avia et al. , Pierangelini et al. , Vágnerová et al.…”

“…The aim is to unravel whether responses to the abiotic interaction are due to local adaptation to specific sets of environmental conditions or to a more generalist increase of phenotypic plasticity (Avia et al. , Pierangelini et al. ).…”

Chromosome-level quality scaffolding of brown algal genomes using InstaGRAAL, a proximity ligation-based scaffolder

“…Together, these steps removed all the misassemblies detected by QUAST (Table 1). To further validate the assembly, we exploited genetic linkage data to search for potential translocations between scaffold extremities [24]. This analysis, now implemented as an option in instaGRAAL, detected such events in the unpolished version but none in the polished assembly.…”

“…A range of genetic and genomic resources have been established for Ectocarpus sp. including a dense genetic map generated with 3,588 SNP markers [24], which was used to comprehensively validate the instaGRAAL assembly.…”