Chloroplast Genome Traits Correlate With Organismal Complexity and Ecological Traits in Chlorophyta

Abstract

A positive relationship between cell size and chloroplast genome size within chloroplast-bearing protists has been hypothesized in the past and shown in some case studies, but other factors influencing chloroplast genome size during the evolution of chlorophyte algae have been less studied. We study chloroplast genome size and GC content as a function of habitats and cell size of chlorophyte algae. The chloroplast genome size of green algae in freshwater, marine and terrestrial habitats was differed significantly, with terrestrial algae having larger chloroplast genome sizes in general. The most important contributor to these enlarged genomes in terrestrial species was the length of intergenic regions. There was no clear difference in the GC content of chloroplast genomes from the three habitats categories. Functional morphological categories also showed differences in chloroplast genome size, with filamentous algae having substantially larger genomes than other forms of algae, and foliose algae had lower GC content than other groups. Chloroplast genome size showed no significant differences among the classes Ulvophyceae, Trebouxiophyceae, and Chlorophyceae, but the GC content of Chlorophyceae chloroplast genomes was significantly lower than that of Ulvophyceae and Trebouxiophyceae. There was a certain positive relationship between chloroplast genome size and cell size for the Chlorophyta as a whole and within each of three major classes. Our data also confirmed previous reports that ancestral quadripartite architecture had been lost many times independently in Chlorophyta. Finally, the comparison of the phenotype of chlorophytes algae harboring plastids uncovered that most of the investigated Chlorophyta algae housed a single plastid per cell.

The origin and early evolution of plants

“…These comparative analyses have demonstrated how genes linked to the development and functioning of vital morphological traits appear during the evolution of Archaeplastida. A selection of these works are discussed here, although many more genome [36][37][38][39][40][41][42] and comparative genomic studies [43][44][45][46][47][48] have been published.…”

Structure and Phylogeny of Chloroplast and Mitochondrial Genomes of a Chlorophycean Algae Pectinodesmus pectinatus (Scenedesmaceae, Sphaeropleales)

“…In 1978, the chloroplast genome of Chlamydomonas reinhardtii was successfully sequenced [8,9]. Since then, hundreds of Life 2022, 12,1912 2 of 19 chloroplast genome of aquatic organisms have been described [10]. The chloroplast genome differs between algal species both in term of the size and the form they take, giving an image of a diverse and quite complicated genetic system occurring inside chloroplasts [10].…”

“…Since then, hundreds of Life 2022, 12,1912 2 of 19 chloroplast genome of aquatic organisms have been described [10]. The chloroplast genome differs between algal species both in term of the size and the form they take, giving an image of a diverse and quite complicated genetic system occurring inside chloroplasts [10]. Determination of chloroplast genomes of chlorophycean algae has offered crucial information for study on the origin and evolution of green algae.…”