Honjo, M. N. | Search bioRxiv

bioRxiv2019

Altered stomatal patterning accompanies a trichome dimorphism in a natural population of Arabidopsis

Trichomes are large epidermal cells on the surface of leaves that are thought to deter herbivores, yet the presence of trichomes can also negatively impact plant growth and reproduction. Stomatal guard cells and trichomes have shared developmental origins, and experimental manipulation of trichome formation can lead to changes in stomatal density. The influence of trichome formation upon stomatal development in natural populations of plants is currently unknown. Here, we show that a natural population of Arabidopsis halleri that includes hairy (trichome-bearing) and glabrous (no trichomes) morphs has differences in stomatal density that are associated with this trichome dimorphism. We found that glabrous morphs had significantly greater stomatal density and stomatal index than hairy morphs. One interpretation is that this arises from a trade-off between the proportions of cells that have trichome and guard cell fates during leaf development. The differences in stomatal density between the two morphs might have impacts upon environmental adaptation, in addition to herbivory deterrence caused by trichome development.

plant biology↗

bioRxiv2019

Seasonal stability and dynamics of DNA methylation in plants in a natural environment

Organisms survive in naturally fluctuating environments by responding to long-term signals, such as seasonality, by filtering out short-term noise. DNA methylation has been considered a stable epigenetic mark but has also been reported to change in response to experimental manipulations of biotic and abiotic factors. However, it is unclear how they behave in natural environments. Here, we analyzed seasonal patterns of genome-wide DNA methylation at a single-base resolution using a single clone from a natural population of the perennial Arabidopsis halleri. The genome-wide pattern of DNA methylation was primarily stable, and most of the repetitive regions were methylated across the year. Although the proportion was small, we detected seasonally methylated cytosines (SeMCs) in the genome. SeMCs in the different contexts showed distinct seasonal patterns of methylation. SeMCs in CHH context were detected predominantly at repetitive sequences in intergenic regions. Additionally, we found that CHH methylation within AhgFLC locus showed a seasonal pattern that was negatively associated with changes in gene expression. Gene-body CG methylation (gbM) itself was generally stable across seasons, but the levels of gbM were positively associated with seasonal stability of RNA expression of the genes. These results suggest the existence of two distinct aspects of DNA methylation in natural environments: sources of epigenetic variation and epigenetic marks for stable gene expression.

plant biology↗