Universität zu Köln

Elfarargi, Ahmed ORCID: 0000-0003-3726-1848 (2023). Genetic basis and adaptive relevance of drought response in Cape Verde Arabidopsis. PhD thesis, Universität zu Köln.

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Abstract

Climate change is predicted to impact precipitation patterns, leading to shorter growing seasons and increased susceptibility to drought in many regions worldwide. These changes significantly threaten plant populations and may result in ecosystem desertification. Understanding the mechanisms enabling species to adapt to such changes is crucial for effective conservation strategies and developing resilient crop varieties. Plants cope with drought through various strategies, including avoidance, escape, and drought tolerance, which can be canalized or plastic, depending on the genetic and environmental context. Understanding the balance between canalization and plasticity is essential for predicting plant responses to future climate change. Here, we investigated the genetic architecture of drought adaptation in natural Cape Verdean Arabidopsis thaliana populations. In Chapter One, we reviewed the impact of climate change on precipitation patterns and its consequences on plant populations, including increased susceptibility to drought and extinction risk. We discussed various strategies plants employ to cope with drought, such as avoidance, escape, and drought tolerance. We also discussed the importance of understanding the balance between canalization and plasticity for predicting plant responses to future climate changes. We also highlighted the significance of genetic adaptations in enabling species to adapt and persist in rapidly changing environments and the potential insights gained from studying A. thaliana populations on the Cape Verde Islands (CVI), which have experienced rapid adaptation and evolutionary rescue in response to drought-prone climates. In Chapter Two, we investigated the evolution of stomatal conductance and water use efficiency (WUE) in an A. thaliana population that colonized an island with a montane cloud scrubland ecosystem characterized by seasonal drought and fog-based precipitation. We found that stomatal conductance increases and WUE decreases in the colonizing population relative to its closest outgroup population from temperate North Africa. Genome-wide association mapping revealed a polygenic basis of trait variation, with a substantial contribution from a nonsynonymous SNP in MAP KINASE 12 (MPK12 G53R), which explains 35% of the phenotypic variance in WUE in the island population. Furthermore, we reconstructed the spatially-explicit evolutionary history of MPK12 53R on the island and demonstrated that this allele increased in frequency due to positive selection as A. thaliana expanded into harsher regions of the island. The findings showed how adaptation shaped quantitative eco-physiological traits in a new precipitation regime defined by low rainfall and high humidity. In Chapter Three, we examined the genetic architecture of variation in growth rate, leaf color, and stomatal patterning in response to precisely controlled water conditions among CVI A. thaliana populations. Genome-wide association mapping analyses revealed that moderately complex genetic architectures with roles for several major effect variants underlie variation in these traits. Furthermore, we found that several identified genes through genetic mapping have pleiotropic functions for complex traits underlying drought stress, highlighting the intricate nature of plant adaptation to these challenging conditions. In conclusion, this work presents a comprehensive analysis of the mechanisms and genetic basis of plant adaptation to drought stress, focusing on the natural A. thaliana populations in the CVI islands. Understanding these mechanisms is critical for predicting species distribution and adaptive responses to drought stress. Furthermore, our findings expand our knowledge of how drought adaptation results from numerous genetic variants, suggesting polygenic adaptation, and reveal that new mutations arise frequently enough to potentially facilitate rapid adaptation in colonizing populations. Lastly, these findings enrich our understanding of plant responses to drought and provide valuable insights for developing effective conservation strategies and resilient crop varieties.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Elfarargi, Ahmed elfarargi@mpipz.mpg.de orcid.org/0000-0003-3726-1848 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-704875
Date:	2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Biology > Institute for Genetics
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language Arabidopsis thaliana, adaptive evolution, seasonal drought, GWA, CVI English UNSPECIFIED English UNSPECIFIED English
Date of oral exam:	11 July 2023
Referee:	Name Academic Title Hancock, Angela Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/70487