Mtr TN Lines Parental Effects
Genetic variation of transgenerational plasticity on seed transcriptome and offspring early response to salinity
In many cases, the environment that parents experience can influence offspring traits early in development, resulting in transgenerational phenotypic plasticity in which the parental environment (PE) can be a predictor of offspring phenotype. One mechanism by which parental environmental experience is transmitted to offspring is through the deposition of long-live RNA transcripts in seeds. PE influence on seed characters is expected to be large because most of seed development and maturation occur while the seed is attached to the parental plant. To study the effects of transgenerational phenotypic plasticity under salt stress, we sequenced the mature seed transcriptome of four selfed M. truncatula inbred genotypes grown in saline and non-saline environments to determine the extent of genetic variation and the response of these genotypes to contrasting PE. Out of 9,321 genes detected in our seed transcriptome, we found evidence of genotype-dependent transcription for 1500 genes, PE-dependent transcription for 321 genes, and the interaction between genotype and PE for 1362 genes. Gene ontology enrichment analysis of the total genes expressed in our seed transcriptome revealed significant enrichment of terms related to stress response, epigenetics, post-embryonic development, symbiosis and post-transcriptional and translational regulation. We observe minimal overlap of PE responsive genes among the four genotypes, which is in agreement with the genotypic variation observed in offspring early developmental traits in response to PE. Some of the most interesting G by PE transcripts code for AGO 4 protein, Dicer-like protein, DNA cytosine 5 methyltransferase, chromatin remodeling proteins, histone modifying factors and DEAD-box ATP-dependent helicase proteins —all of which have been implicated in RNA-directed DNA methylation pathway. This pathway has been well documented to mediate de novo methylation in plants and studies have suggested its involvement in transgenerational epigenetic inheritance.