Spontaneous mutation rate as a source of diversity for improving desirable traits in cultured microalgae

Abstract

Mutations are the main origin of the biodiversity and biological innovations across the tree of life. The number of mutations in a population depends of the mutation rate, noted μ, a key parameter for understanding the evolutionary and adaptive capacity of a species. New mutations are submitted to selection and drift and their probability of fixation in a population depends on their advantageous, deleterious or neutral fitness effect. This process occurs in natural populations, but also in any lab cultures. In this context, the role of spontaneous mutations in the generation of genetic diversity in cultured algae has so far been overlooked, despite its influence on the acquisition and maintenance of desirable phenotypic traits. Several algal species that have a high biotechnological potential, such those producing high-value molecules, might be improved by domestication and oriented selection by experimental evolution. Here, we provide the first estimation of the spontaneous mutation rate, μ, in Picochlorum costavermella (Trebouxiophyceae), a green alga with many potential biotechnological applications. Its spontaneous mutation rate is μ = 10.12 × 10 −10 (CI Poisson distribution, μ = 6.3-15.4 × 10 −10) mutations per nucleotide per genome per generation. This is one of the highest mutation rates reported for a unicellular eukaryote.

Evolution of Codon Usage Bias in Diatoms

“…Furthermore, the mutation spectrum and rate can vary depending on the environment [63]. Thus, plankton species may exhibit strong variation in mutation rate and spectrum [14,64,65,66,67], and extending the results of the only direct analysis of mutations in diatoms (in P. tricornutum [42]) to other species has to be done with caution. The mutation spectrum variation, both in bias strength and direction, may cause a shift in the mutation-drift balance and affect codon usage [68].…”

First Estimation of the Spontaneous Mutation Rate in Diatoms

“…2017); Chlamydomonas reinhardtii (Ness et al. 2015); Picochlorum costavermella (Krasovec et al. 2018); Pt : Phaeodactylum tricornutum ; Paramecium tetraurelia (Sung et al.…”

High rates of spontaneous chromosomal duplications unravel dosage compensation by translational regulation

“…However, these mutations did not lead to a fitness increase in all disomic strains, and a few disomic strains with higher growth rates did not harbour any non-synonymous mutations. The previously identified point mutations from each MA line carrying a WCD in this study (Table S2) (Krasovec et al 2017, 2018a, 2019) are unlikely to impact the aneuploidy tolerance for two reasons. First, some lines such as Mp03, Bp28b, Bp26 or Bp25 did not carry any additional point mutation as compared to MA lines without WCD.…”

“…The principle is to follow mutation accumulation lines originated from an inbred couple (such as in Drosophila ) or a clone (such as in yeast) under minimal selection obtain by serial bottlenecks during dozen to thousands generations (Halligan and Keightley 2009). Mutation accumulation experiments were done previously by maintaining 12 to 40 mutation accumulations line which accumulated 1,595 to 17,250 generations (Krasovec et al 2017, 2018a, 2019). Whole chromosome duplications detected here are part of structural mutations, such as large insertions-deletions, inversions or chromosome rearrangements and may have huge phenotypical effect, much more than a nucleotide or short insertion-deletion mutations because they impact a larger proportion of the genome.…”