Population-level consequences of inheritable somatic mutations and the evolution of mutation rates in plants

Abstract

Inbreeding depression, that is the decrease in fitness of inbred relative to outbred individuals, was shown to increase strongly as life expectancy increases in plants. Because plants are thought to not have a separated germline, it was proposed that this pattern could be generated by somatic mutations accumulating during growth, since larger and more long-lived species have more opportunities for mutations to accumulate. A key determinant of the role of somatic mutations is the rate at which they occur, which probably differs between species because mutation rates may evolve differently in species with constrasting life histories. In this paper, I study the evolution of the mutation rates in plants, and consider the population-level consequences of inheritable somatic mutations given this evolution. I show that despite substantially lower somatic and meiotic mutation rates, more long-lived species still tend to accumulate larger amounts of deleterious mutations because of the increased number of opportunities they have to acquire mutations during growth, leading to higher levels of inbreeding depression in these species. However, the magnitude of this increase depends strongly on how mutagenic meiosis is relative to growth, to the point of being close to non-existent in some situations.

Frequent spontaneous structural rearrangements promote rapid genome diversification in a Brassica napus F1 generation

“…Species are expected to have low to intermediate mutation rates to avoid loss of required biological information (Lesaffre, 2021) and retain fitness across generations. Nevertheless, mutations within populations can lead to significant functional changes.…”

“…However, the F1 plant F1 replicate 1, which was found to carry a unique NHRE between chromosomes C08 and A09 (Supplementary Figures 11-13), was similar to the maternal line Express 617 in terms of height, digital biomass and leaf area throughout its life cycle, and dissimilar to the other 11 sister plants for these characters despite growing side-by-side in the same controlled environment. Because many genes were impacted by the various SV events, it is likely that other macro and microphenotypic traits could be affected by the spontaneous rearrangements in individual plants, although gene redundancy in the allopolyploid B. napus genome likely balances or buffers many effects from gene loss or inactivation due to rearrangements (Lesaffre, 2021). Nevertheless, the plant with a putative SV-driven impact on height, leaf area and biomass demonstrates the potential adaptive implications of frequent, spontaneous structural rearrangements as a source of novel genetic variation in a recent allopolyploid species with a narrow genetic diversity due to polyploidization and breeding bottlenecks.…”

Frequent spontaneous structural rearrangements promote rapid genome diversification in a Brassica napus F1 generation

“…Genomic rearrangements have also been associated to changes in flowering time (Schiessl et al, 2019; Chawla et al, 2021; Vollrath et al, 2021a), seed quality (Stein et al, 2017) and disease resistance (Gabur et al, 2020; Vollrath et al, 2021b) in B. napus cultivars. Intragenic structural variations within cultivars have also been reported in maize and wheat (Lesaffre, 2021). To our knowledge the present study is the first to clearly describe and validate spontaneous genomic rearrangements in F1 sister plants derived from a single meiosis in B. napus .…”

“…Genomic rearrangements have also been associated to changes in flowering time (Schiessl et al, 2019;Chawla et al, 2021;Vollrath et al, 2021a), seed quality (Stein et al, 2017) and disease resistance (Gabur et al, 2020;Vollrath et al, 2021b) in B. napus cultivars. Intragenic structural variations within cultivars have also been reported in maize and wheat (Lesaffre, 2021)…”

“…However, the F1 plant F1 replicate 1, which was found to carry a unique NHRE between chromosomes C08 and A09 , was similar to the maternal line Express 617 in terms of height, digital biomass and leaf area throughout its life cycle, despite growing side-byside in the same controlled environment . Because many genes were impacted by the various SV events,, it is likely that other macro and micro-phenotypic traits could be affected by the spontaneous rearrangements in individual plants, although gene redundancy in the alllopolyploid B. napus genome likely balances or buffers many effects from gene loss or inactivation due to rearrangements (Lesaffre, 2021). Nevertheless, the plant with a putative SV-driven impact on height, leaf area and biomass demonstrates the potential adaptive implications of frequent, spontaneous, transgenerational structural rearrangements as a source of novel genetic variation in a recent allopolyploid species with a narrow genetic diversity due to polyploidization and breeding bottlenecks (Samans et al, 2017).…”