Changes in genomic 5-methylcytosine level mirror the response of orthodox (Acer platanoides L.) and recalcitrant (Acer pseudoplatanus L.) seeds to severe desiccation

Abstract

Poor storability of recalcitrant seeds is due to their inability to tolerate low moisture content. Understanding the processes underlying their recalcitrance is a prerequisite to developing a maintenance strategy and prolonging their lifespan. Multiple studies have investigated the differences between orthodox (desiccation-tolerant) and recalcitrant (desiccation-sensitive) seeds. Information on epigenetic regulation, however, is lacking and thus limits our understanding of the processes defining the physiology of seeds. In the present comparative study, changes in the global levels of 5-methylcytosine (m5C) in orthodox and recalcitrant seeds of Acer platanoides L. and Acer pseudoplatanus L. were characterized during progressive stages of severe drying. Concomitant with their differential sensitivity to desiccation stress, we demonstrate variation in the response of embryonic axes and cotyledons to water deficit at the level of DNA methylation. Results indicate that desiccation-induced changes in m5C are both tissue- and seed category-specific and are highly correlated with recalcitrant seed viability. Moreover, we demonstrate that m5C global changes in response to desiccation are not retained in DNA isolated from seedlings, except in seedlings that are derived from strongly desiccated orthodox seeds (moisture content of 3.5%). Finally, the potential utilization of m5C status as a universal seed viability marker is discussed.

Genetic and Epigenetic Stability in Rye Seeds under Different Storage Conditions: Ageing and Oxygen Effect

“…Changes in the seed methylation status during storage have been studied before in orthodox and recalcitrant seeds [25][26][27]32]. In the present work, epigenetic changes detected on rye were up to 15-30% in stored seeds, even during the earlier stages of deterioration, and up to 13-27% in seedlings produced from stored seeds.…”

“…Recalcitrant seeds suffer viability loss during desiccation. Epigenetic changes associated with drying are highly correlated with viability loss of Acer pseudoplatanus recalcitrant seeds but not in A. platanoides orthodox seeds [26]. In that study, methylation changes in response to desiccation were not retained in DNA isolated from seedlings, except in seedlings that were derived from strongly desiccated orthodox seeds (3.5% wc).…”

“…Comparing adult plant tissues to juvenile ones, results suggest that the methylation status of genomic DNA can vary during plant ageing [23,24]. In seeds, epigenetic changes have been detected after drying, both in orthodox and recalcitrant seeds [25,26], and also in seedlings obtained from them [27]. However, epigenetic stability during seed storage and ageing have not been studied extensively, especially regarding what could happen to the next generation.…”

A new approach towards the so-called recalcitrant seeds

“…Among the groups that persist in the area, the panel that was demonstrated up to two decades ago did not change much afterward (Figure 1). The majority of the studies are basically focused on desiccation tolerance Corsato et al, 2012;Chapell et al, 2015;Amoedo and Ferraz, 2017;Gasparin et al, 2017;Subbiah et al, 2017;Chandra and Keshavkant, 2018;Plitta-Michalak et al, 2018), identification of storage behavior (Comin et al, 2014;Joshi et al, 2015;Vicente et al, 2016; 2017; Plitta-Michalak et al, 2018), analysis of deterioration and evaluation of techniques to extend the storage period (Barbedo and Cicero, 2000;Andréo et al, 2006;Bonjovani and Barbedo, 2008;Ballesteros et al, 2014;Lan et al, 2014;Parkhey et al, 2014;Garcia et al, 2015;Ming-Yue et al, 2015;Umarani et al, 2015;Araldi et al, 2016;Hossel et al, 2016;Félix et al, 2017), and rare studying other aspects such as seed maturation (Avila et al, 2009;Lamarca et al, 2013b;Mata et al, 2013;Schultz et al, 2014;Araldi and Coelho, 2015;Shibata and Coelho, 2016;Souza et al, 2018a, b), whose importance will be discussed later, and ecological (Ramlall et al, 2015;Vaz et al, 2016;Porto et al, 2018) or germinative aspects (Moothoo-Padayachie et al, 2016). An analysis, albeit superficial, of studies developed in Brazil and in the world shows small differences.…”

“…Studies that seek to increase the storage period, despite important advances, still does not achieve substantial gains, obtaining an extension for a few months or, exceptionally, years. Some advances have been obtained, for instance, with fungus control (Figure 2A) during storage, one of the main problems since seeds are stored moist and often at temperatures that do not totally inhibit the development of microorganisms (Oliveira et al, 2011;Parisi et al, 2013;Françoso and Barbedo, 2014;Hennipman et al, 2017). Studies on desiccation tolerance, although essential, are not exclusive to seeds, but include ferns (Fallard et al, 2018), mosses (Xiao et al, 2018), fungi (Jackson et al, 2006), algae (Cardon et al, 2018), and even animals such as insects (Kellermann et al, 2018) and amphibians (Eads et al, 2012), evidently each within certain limits of interest in the specific areas.…”