Hydrangea DNA Methylation Caused by pH Substrate Changes to Modify Sepal Colour is Detected by MSAP and ISSR Markers

Julio Y. Anaya-Covarrubias,Martha Escoto-Delgadillo,Ramón Rodríguez-Macías,Nerea Larranaga,Martha I. Torres-Morán,Norma Almaráz-Abarca

doi:10.3390/agronomy9120871

Julio Y. Anaya-Covarrubias, Martha Escoto-Delgadillo + Show 4 more

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https://doi.org/10.3390/agronomy9120871

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Abstract

The hydrangea (Hydrangea macrophylla (Thunb). Ser.) is an ornamental species with great market potential. It is known for its ability to change the colour of its inflorescence, according to the pH of the culture substrate. The molecular mechanisms that underlie these changes are still unclear. It is known that epigenetic mechanisms, such as DNA methylation, play an important role in genetic expression, so they could be responsible for this phenomenon in hydrangea. In the present study, the molecular markers ISSR (Inter Simple Sequence Repeat) and MSAP (Methyl-Sensitive Amplification Polymorphism) were used to detect molecular changes in the genome of hydrangea plants that were cultivated under different pH levels to modify the colour of the sepals. The results showed a correspondence between the methylation signal measured with MSAP and amplification ISSR patterns when compared before and after the modification of pH culture substrates. These results suggest that DNA methylation might be involved as a molecular mechanism underlying the colour change of hydrangea sepals in response to a differential pH in the substrate. In addition, the results pave the way to study the relationship between DNA methylation and ISSR marker profiles.

Highlights

The genera Hydrangea, native to Japan, from the Hydrangeae family, was divided in two sections: Hydrangea McClint. and Cornidia Engl., which englobe 25 species in total and numerous subspecies [1].In addition, many cultivars have been developed and named as species, which complicates the taxonomy of this family [2]
Plants have a rooting period of 10 days under greenhouse, after which the plants were divided in two treatments of 14 plants. Afterwards, they were placed in 20.32 cm pots with two kinds of substratum; a substratum that was composed by 50% organic soil and 50% fine pumice (AL) producing Alkaline pH, and a substratum composed by 60% peat moss and 40% fine pumice (AC) producing Acid pH
The objective of the present work was to corroborate the change of the hydrangea colour sepals when the pH of the substratum is modified and relate these changes with the DNA methylation as an epigenetic mechanism

Summary

Introduction

Many cultivars have been developed and named as species, which complicates the taxonomy of this family [2]. Many of these species are marketed as flower of court, due to its long lasting characteristic umbelliform cyme inflorescences [3]. The inflorescences are complex and polymorphic, since they are composed of small fertile flowers and other sterile with large coloured sepals, which are often much more visible than the petals [4,5,6]. These species’ ability to change the colour of the sepals as a consequence of the pH in the culture substrate is Agronomy 2019, 9, 871; doi:10.3390/agronomy9120871 www.mdpi.com/journal/agronomy

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