Tracing evolutionary patterns across the green lineage with respect to protein families and pathways in response to stress

by Amra Dhabalia Ashok
Doctoral thesis
Date of Examination:2023-10-09
Date of issue:2024-08-22
Advisor:Prof. Dr. Jan de Vries
Referee:Prof. Dr. Jan de Vries
Referee:Prof. Dr. Christoph Bleidorn
Persistent Address: http://dx.doi.org/10.53846/goediss-10689

 

 

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Abstract

English

The evolutionary history of Chloroplastida is unique, as it includes the emergence of those organisms that make up the macroscopic flora on land: the land plants (embryophytes). The land plants arose from a singular evolutionary event. The earliest land plants had the genetic molecular toolkit to not just survive but to thrive on land, undergoing an, among photosynthetic eukaryotes, unparalleled diversification. What happened? Since there is no fossil record of the possible earliest land plants, it is essential to explore this scientific question through its genetic chassis. The closest extant relatives of land plants are the streptophyte algae. These streptophyte algae must be studied in a comparative and complementing approach with the diversity of embryophytes in order to infer the earliest land plants. Great evolutionary change can stem from environmental changes. These changes can bring about heritable diversification in functions that builds on the emergence of moldable genetic material through processes such as whole genome duplication. What follows is often sub- and neo-functionalization of some genes. But what if we sought to understand this process by breaking it into smaller units. Protein domains can be considered the building blocks of protein function—their combination define the interplay between structure and function in protein. Proteins with a similar combination of protein domains form a protein family. A protein family is a large group of functionally related proteins. The closeness of species and lineages is determined by the closeness in the type of protein families between them. Thus, a comparative genomic approach that builds on the inferred proteomes can help understanding the singular evolutionary event of occurrence and diversity of land plants. Through this thesis, the diversity is captured to understand the biological innovations that ushered in the emergence of land plants. Their shared and diversified toolkit is explored and set in context by comparison with their algal relatives. Since stress is a key threshold to sustain before diversifying, this thesis explores the molecular toolkit in terms of pathways and protein families that respond to stress.
Keywords: Streptophyta; Green lineage; Stress-responsive networks; Mosaic evolution; Exaptation; Comparative analysis; Sequence similarity networks
 
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