Epigenetic Changes Accompany Developmental Programmed Cell Death in Tapetum Cells

Abstract

The tapetum, the nursing tissue inside anthers, undergoes cellular degradation by programmed cell death (PCD) during late stages of microspore-early pollen development. Despite the key function of tapetum, little is known about the molecular mechanisms regulating this cell death process in which profound nuclear and chromatin changes occur. Epigenetic features (DNA methylation and histone modifications) have been revealed as hallmarks that establish the functional status of chromatin domains, but no evidence on the epigenetic regulation of PCD has been reported. DNA methylation is accomplished by DNA methyltransferases, among which DNA methyl transferase 1 (MET1) constitutes one of the CG maintenance methyltransferase in plants, also showing de novo methyltransferase activity. In this work, the changes in epigenetic marks during the PCD of tapetal cells have been investigated by a multidisciplinary approach to reveal the dynamics of DNA methylation and the pattern of expression of MET1 in relation to the main cellular changes of this PCD process which have also been characterized in two species, Brassica napus and Nicotiana tabacum. The results showed that tapetum PCD progresses with the increase in global DNA methylation and MET1 expression, epigenetic changes that accompanied the reorganization of the nuclear architecture and a high chromatin condensation, activity of caspase 3-like proteases and Cyt c release. The reported data indicate a relationship between the PCD process and the DNA methylation dynamics and MET1 expression in tapetal cells, suggesting a possible new role for the epigenetic marks in the nuclear events occurring during this cell death process and providing new insights into the epigenetic control of plant PCD.

Cork Oak Young and Traumatic Periderms Show PCD Typical Chromatin Patterns but Different Chromatin-Modifying Genes Expression

“…Similar to cork cells differentiation are the changes in nuclear morphology and chromatin organization found amongst the most typical structural features in cells undergoing PCD [reviewed in (Van Hautegem et al, 2014; Latrasse et al, 2016)]. These alterations accompanied by increased levels and a change in the distribution of DNA methylation in differentiating cork cells has also been observed in tapetum cells PCD correlating with an up-regulation of MET1 (Solís et al, 2014), responsible for CpG methylation maintenance in cycling cells (Huang et al, 2010). Indeed, QsMET1 was amongst the genes with higher levels of relative expression in the cork tissue contradicting, however, previous results in corks with different qualities (Ramos et al, 2013) where was argued that QsMET2 might be substituting QsMET1 function to maintain the CpG methylation during phellogen activity.…”

Histone Deacetylase Is Required for GA-Induced Programmed Cell Death in Maize Aleurone Layers

“…Thus, reduced acetylation might be implicated in the cytological changes of aleurone cell death. DNA methylation and histone monoubiquitination have been shown to play an important role in regulating PCD in tapetum (Solís et al, 2014;Cao et al, 2015).…”

Changes in DNA Methylation Levels and Nuclear Distribution Patterns after Microspore Reprogramming to Embryogenesis in Barley

“…Genomic DNA was extracted from microspores and mature pollen directly isolated from anthers, and from different microspore culture stages using a plant genomic DNA extraction kit (DNeasy Plant Mini, Qiagen) as described [Solís et al, 2014]. A MethylFlash Methylated DNA Quantification Kit (Colorimetric) (Epigentek, N.Y., USA) was employed according to the manufacturer's instruction using 200 ng of genomic DNA for each sample [Li and Liu, 2011;Testillano et al, 2013] for the quantification of DNA methylation.…”