Expression analysis of epigenetic and abscisic acid-related genes during maturation of Quercus suber somatic embryos

Abstract

Clonal propagation of Quercus suber via somatic embryogenesis is an alternative to conventional tree propagation methods; however, complete maturation of somatic embryos is considered the major bottleneck for mass propagation of Quercus species. During somatic embryogenesis, embryo development and maturation are controlled by signaling pathways that integrate information from genetic and epigenetic programs as well as hormonal signals. Therefore, in this study genes were identified related to epigenetic regulation and the abscisic acid (ABA) pathway during development and maturation of cork oak somatic embryos. A total of eight expressed sequence tags were obtained of genes encoding a 9-cisepoxycarotenoid dioxygenase (NCED), two histone deacetylases (HDA6 and HDA19), two histone monoubiquitinases (HUB1 and HUB2), a histone H3 kinase (AUR3) as well as genes related to chromatin remodeling processes PICKLE and VP1/ABSCISIC ACID INSENSI-TIVE 3-LIKE 1 (VAL1). The analysis of the expression patterns of selected genes during different developmental stages indicated that QsNCED3 may play a role in ABA synthesis during embryogenesis. The change in the expression levels for all seven genes associated with epigenetic regulation showed that QsHUB1 and QsHUB2 may have a role in ABA signalling while QsHDA6 and QsHDA19 could act in different pathways than in Arabidopsis. Furthermore, expression levels of QsAUR3 indicated that histone phosphorylation is an early epigenetic mark in Q. suber somatic embryos while QsPICKLE and QsVAL1 may be necessary for the correct development of cork oak somatic embryos.

Epigenetic Regulation of Auxin-Induced Somatic Embryogenesis in Plants

“…Consistently, AuxREs have been identified in the promoters of the majority of the TF genes of upregulated expression during SE induced in Arabidopsis with the HDAC-inhibitor, trichostatin A (TSA) [22]. Evidence of the contribution of the (de)acetylation of histones to the in vitro-induced embryogenic transition also provides the differential expression of several members of the HDAC and HAT gene families in the SE transcriptomes of plants [125,[167][168][169]. Two of the deacetylases, HDAC6 and HDAC19, seem to be of particular importance in SE induction as the hdac6/hdac19 mutant plants showed somatic embryo development on their leaves [23].…”

Somatic Embryogenesis: Fundamental Aspects and Applications

“…Recently, it was discovered that genes necessary for embryo maturation are under the regulation of histone H3 modifications and chromatin remodeling (Pérez et al 2015a). The in vitro culture of Q. suber L. via SE is an alternative to conventional methods of reproduction that solve the problem of its long reproductive propagation and irregular seed yield.…”

The role of chromatin modifications in somatic embryogenesis in plants

“…This epigenetic mechanism during the induction of SE has been documented in at least 18 species from 12 families ( Table 2 ). However, in only four of these species have the modifications in histones been determined ( Nic-Can et al, 2013 ; Rodríguez-Sanz et al, 2014b ; Pérez et al, 2015a ; Wickramasuriya and Dunwell, 2015 ).…”

“…The expression pattern of several genes related to chromatin modification and remodeling [two histone deacetylases (HDACs), HDA6 and HDA19 , two histone monoubiquitinases ( HUB1 and HUB2 ), a histone H3 kinase ( AUR3 ), PICKLE and VP1 / ABSCISIC ACID INSNSITIVE 3-LIKE 1 ( VAL1 )], have been studied during the SE process of Q. suber ( Pérez et al, 2015a ). It was found that QsHDA19 decreases its expression as soon as the callus begins its differentiation, followed by a steady increase from immature cotyledonary embryo to an embryo with the cotyledons fully differentiated.…”