Embryogenic potential and expression of embryogenesis-related genes in conifers are affected by treatment with a histone deacetylase inhibitor

Abstract

Somatic embryogenesis is used for vegetative propagation of conifers. Embryogenic cultures can be established from zygotic embryos; however, the embryogenic potential decreases during germination. In Arabidopsis, LEAFY COTYLEDON (LEC) genes are expressed during the embryonic stage, and must be repressed to allow germination. Treatment with the histone deacetylase inhibitor trichostatin A (TSA) causes de-repression of LEC genes. ABSCISICACID3 (ABI3) and its Zeamays ortholog VIVIPAROUS1 (VP1) act together with the LEC genes to promote embryo maturation. In this study, we have asked the question whether TSA treatment in a conifer affects the embryogenic potential and the expression of embryogenesis-related genes. We isolated two conifer LEC1-type HAP3 genes, HAP3A and HAP3B, from Picea abies and Pinus sylvestris. A comparative phylogenetic analysis of plant HAP3 genes suggests that HAP3A and HAP3B are paralogous genes originating from a duplication event in the conifer lineage. The expression of HAP3A is high, in both somatic and zygotic embryos, during early embryo development, but decreases during late embryogeny. In contrast, the expression of VP1 is initially low but increases during late embryogeny. After exposure to TSA, germinating somatic embryos of P. abies maintain the competence to differentiate embryogenic tissue, and simultaneously the germination progression is partially inhibited. Furthermore, when embryogenic cultures of P. abies are exposed to TSA during embryo maturation, the maturation process is arrested and the expression levels of PaHAP3A and PaVP1 are maintained, suggesting a possible link between chromatin structure and expression of embryogenesis-related genes in conifers.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-011-1418-8) contains supplementary material, which is available to authorized users.

Recent progress in the understanding of tissue culture-induced genome level changes in plants and potential applications

“…Trichostatin treatment inhibited germination progression of embryos such that they could efficiently initiate proliferative embryogenic calli in a suitable medium. Maturation of somatic embryos was also blocked by this treatment and this was mediated by affecting the expression of embryogenesis-related leafy cotyledon genes, possibly via chromatin modification (Uddenberg et al 2011).…”

“…Chemicals that can potentially modify the epigenetic state of plant cells have been utilized recently in conifer cultures to improve embryogenic efficiency (Uddenberg et al 2011). Trichostatin treatment inhibited germination progression of embryos such that they could efficiently initiate proliferative embryogenic calli in a suitable medium.…”

A transcriptional view on somatic embryogenesis

“…Germinating spruce somatic embryos treated with TSA maintain their embryo identity rather than converting to seedlings (Uddenberg et al., 2011). TSA was also found to enhance haploid embryo induction from heat‐stressed in vitro cultured male gametophytes in B. napus (Li et al., 2014).…”

Cryopreservation of embryogenic tissues from mature holm oak trees

“…Several authors described changes at gene transcription level such as DNA methylation or histone modification linked to the embryogenic response [60], somatic embryo maturation [55] and complete somatic embryo development and conversion [37]. Such changes were also observed in the different steps of the cryopreservation procedure [17].…”