Genotypic variation in the persistence of transgenerational responses to seasonal cues*

Abstract

Phenotypes respond to environments experienced directly by an individual, via phenotypic plasticity, or to the environment experienced by ancestors, via transgenerational environmental effects. The adaptive value of environmental effects depends not only on the strength and direction of the induced response but also on how long the response persists within and across generations, and how stably it is expressed across environments that are encountered subsequently. Little is known about the genetic basis of those distinct components, or even whether they exhibit genetic variation. We tested for genetic differences in the inducibility, temporal persistence, and environmental stability of transgenerational environmental effects in Arabidopsis thaliana. Genetic variation existed in the inducibility of transgenerational effects on traits expressed across the life cycle. Surprisingly, the persistence of transgenerational effects into the third generation was uncorrelated with their induction in the second generation. Although environmental effects for some traits in some genotypes weakened over successive generations, others were stronger or even in the opposite direction in more distant generations. Therefore, transgenerational effects in more distant generations are not merely caused by the retention or dissipation of those expressed in prior generations, but they may be genetically independent traits with the potential to evolve independently.

Digest: Transgenerational stress memory mechanisms in Arabidopsis thaliana *

“…In line with their hypothesis of a genetic basis of stress memory, Alvarez et al. (2020) showed the genotype of A. thaliana influenced the induction of environmental effects on phenotypic traits. However, contrary to the hypothesis that phenotypes would dissipate in the third generation without refamiliarization of the stressor in the second, the researchers found some accessions retained their phenotype, some exhibited stronger phenotypes than the previous generation, and some accessions even showed phenotypic plasticity in the opposite direction.…”

“…The study by Alvarez et al. (2020) does not suggest HR and PM to be the main or only mechanism of transgenerational stress because certain accessions had reversible phenotypic plasticity, which is not indicative of permanent genomic changes. However, this study used a mild heat stressor indicative of differing climates, rather than a strong, stressful cue as used in previous studies (Yao et al 2013)…”

“…Stressed A. thaliana plants have increased homologous recombination (HR) and point mutations (PM), but impaired recognition and repair of double stranded breaks can inhibit the effects of transgenerational stress on HR and PM (Yao et al 2013). The study by Alvarez et al (2020) does not suggest HR and PM to be the main or only mechanism of transgenerational stress because certain accessions had reversible phenotypic plasticity, which is not indicative of permanent genomic changes. However, this study used a mild heat stressor indicative of differing climates, rather than a strong, stressful cue as used in previous studies (Yao et al 2013) A growing body of evidence suggests epigenetic regulation plays a large role in transgenerational stress memory in A. thaliana.…”

“…In this study, Alvarez et al. (2020) grew eight accessions of A. thaliana in controlled conditions while manipulating various experimental conditions to detect several phenotypic outcomes in successive generations. The authors manipulated seed germination temperature, thermal regime, and vernalization in different genotypes to determine the effect on three components of transgenerational plasticity: induction, temporal persistence, and environmental stability.…”

Mimulus sRNAs Are Wound Responsive and Associated with Transgenerationally Plastic Genes but Rarely Both

“…Meiotic transmission of epigenetic markings resulting from environmental cues provides a mechanism through which plastic responses to the environment can be transmitted from one generation to the next (transgenerational plasticity [ 6 ]). While plant germline cells do undergo a number of rounds of epigenetic reprogramming prior to the formation of a new seed [ 7 ], it is clear that environmental conditions experienced by parents can alter phenotypes [ 8 , 9 , 10 , 11 ], epigenetic profiles [ 4 , 10 , 12 , 13 ] and gene expression [ 14 , 15 , 16 ] in the next generation. Importantly, autocorrelation between offspring and parent environment can favor mechanisms that establish such patterns of transgenerational plasticity [ 17 , 18 ], perhaps leading to natural selection that either favors or disfavors this transmission depending on local environmental patterns [ 11 ].…”