DNA Methylation as an Early Indicator of Aging in Stored Seeds of “Exceptional” Species Populus nigra L.

Abstract

Ex situ preservation of genetic resources is an essential strategy for the conservation of plant biodiversity. In this regard, seed storage is the most convenient and efficient way of preserving germplasm for future plant breeding efforts. A better understanding of the molecular changes that occur during seed desiccation and aging is necessary to improve conservation protocols, as well as real-time methods for monitoring seed quality. In the present study, we assessed changes in the level of genomic 5-methylcytosine (5mC) in seeds of Populus nigra L. by 2D-TLC. Epigenetic changes were characterized in response to several seed storage regimes. Our results demonstrate that P. nigra seeds represent an intermediate type of post-harvest behavior, falling between recalcitrant and orthodox seeds. This was also true for the epigenetic response of P. nigra seeds to external factors. A crucial question is whether aging in seeds is initiated by a decline in the level of 5mC, or if epigenetic changes induce a process that leads to deterioration. In our study, we demonstrate for the first time that 5mC levels decrease during storage and that the decline can be detected before any changes in seed germination are evident. Once P. nigra seeds reached an 8–10% reduction in the level of 5mC, a substantial decrease in germination occurred. The decline in the level of 5mC appears to be a critical parameter underlying the rapid deterioration of intermediate seeds. Thus, the measurement of 5mC can be a fast, real-time method for assessing asymptomatic aging in stored seeds.

Identification of DNA Methylation Changes in European Beech Seeds during Desiccation and Storage

“…Conservation of seeds is the primary method of choice when attempting to preserve the gene pool of a plant species [ 20 , 30 , 33 , 34 , 35 , 36 ]; therefore, deterioration of seeds during storage has profound influences on agriculture and conservation efforts [ 37 ]. Seed aging processes resulting in viability decline and final decrease of plantlet amount are dependent on storage conditions, which are the temperature and RH that determine seed MC.…”

“…Studying the changes in plant methylome under stressed conditions has become an essential issue in order to better understand the molecular mechanisms underlying plant stress responses [ 24 , 25 ]. Previously, we showed desiccation and aging related changes in global m 5 C levels in seeds of recalcitrant, orthodox, and short-lived intermediate categories [ 11 , 26 , 27 , 28 , 29 , 30 ]. Importantly, in our last research entire poplar ( Populus nigra L.) seeds without separation for embryonic axes and cotyledons were tested.…”

“…Importantly, in our last research entire poplar ( Populus nigra L.) seeds without separation for embryonic axes and cotyledons were tested. Poplar seeds, contrary to beech seeds, have a low amount of storage lipids and contain developed chloroplasts that may be the main source of oxidative stress leading to the fast aging in those seeds [ 30 , 31 , 32 ]. The current work shows for the first time the impact of applied treatment (desiccation and storage) on common beech intermediate seed methylome.…”

Choosing the Right Path for the Successful Storage of Seeds

“…Consequently, there is a huge need for new biochemical or molecular markers of seed viability that improve the process of monitoring plant material during storage in gene banks and to help with the understanding of the concomitant aging process occurring in seeds. These studies have developed rapidly over the last decade and substantiate the importance of volatile organic compounds [ 94 , 95 , 98 ], proteomic studies [ 191 ], RNA integrity [ 192 , 193 , 194 , 195 , 196 ] and DNA damage markers or epigenetic marks [ 96 , 97 , 99 , 190 , 197 , 198 , 199 , 200 ] that are highly promising and should be more widely explored.…”

“…Importantly, a meta-analysis of germination data indicated that predicted germinability was often higher than actual values that were experimentally obtained [ 87 ]. Therefore, further research which focuses on obtaining more accurate predictions of orthodox seed longevity based upon the testing of new markers of seed viability and quality in real-time appear warranted and necessary [ 91 , 94 , 95 , 96 , 97 , 98 , 99 ].…”