Phase-change related epigenetic and physiological changes in Pinus radiata D. Don

Abstract

DNA methylation and polyamine levels were analysed before and after Pinus radiata D. Don. phase change in order to identify possible molecular and physiological phase markers. Juvenile individuals (without reproductive ability) were characterised by a degree of DNA methylation of 30-35% and a ratio of free polyamines to perchloric acid-soluble polyamine conjugates greater than 1, while mature trees (with reproductive ability) had 60% 5-methylcytosine and a ratio of free polyamines to perchloric acid-soluble polyamine conjugates of less than 1. Results obtained with trees that attained reproductive capacity during the experimental period confirmed that changes in the degree of DNA methylation and polyamine concentrations found among juvenile and mature states come about immediately after the phase change. We suggest that both indicators may be associated with the loss of morphogenic ability during ageing, particularly after phase change, through a number of molecular interactions, which are subsequently discussed.

Photochemical Efficiency during the Establishment and Consolidation Phases of in Vitro Pinus radiata Micrograft Made from Scions of Different Ontogenetic Age

“…The decrease in vigor and adventitious organs formation capacity are responses associated with the tissue maturation stage [4]. Hence, basal scions must present higher morphogenic capacities than apical ones, because their younger ontogenetic age determined by the proximity to the mother cell located at the collar of the ortet [5] [6]. In the consolidation phase we found that juvenile traits of ontogenically young tissues can be preserved in basal scions.…”

“…This higher photochemical activity is a proxy of higher CO 2 assimilation capacity, and therefore of greater photosynthetic performance and potentially faster growth [18] [20] [21]. Additionally higher Fv/Fm reflects an ontogenetic age gradient of shoot tips morphogenic competence, where basal meristematic shoot tips present higher morphogenic capacities than apical ones [5] [6]. Finally, based on our results, we conclude that Fv/Fm can be an indicator of the micrograft's development according to the shoot tips position in the ortet and can be a useful indicator of the physiological stage of scions during micrograft transition from establishment to consolidation.…”

“…It has been suggested that the decline in morphogenic capacity could be due to the loss in competence at the cellular level and it is highly likely that this phenomenon causes changes in gene transcription [8]. In vitro propagation methods may induce reinvigoration of advanced physiological tissue and renewal of ontogenetically adult P. radiata [3] [6], and in this way avoid the problems associated to the lost of morphogenic capacity. This reinvigoration includes anatomical, molecular and epigenetic changes which reflect characteristic juvenile individual's protein patterns, DNA methylation and polyamine content [6] [9].…”

“…In vitro propagation methods may induce reinvigoration of advanced physiological tissue and renewal of ontogenetically adult P. radiata [3] [6], and in this way avoid the problems associated to the lost of morphogenic capacity. This reinvigoration includes anatomical, molecular and epigenetic changes which reflect characteristic juvenile individual's protein patterns, DNA methylation and polyamine content [6] [9]. Altogether, the reversion of several adult phenotypic traits towards more juvenile stages and the recovery of tissue morphogenic capabilities allow the cloning of selected adult trees [6] [9] [10].…”

“…This reinvigoration includes anatomical, molecular and epigenetic changes which reflect characteristic juvenile individual's protein patterns, DNA methylation and polyamine content [6] [9]. Altogether, the reversion of several adult phenotypic traits towards more juvenile stages and the recovery of tissue morphogenic capabilities allow the cloning of selected adult trees [6] [9] [10]. One tissue reinvigoration techniques is the in vitro micrograft, which has been tested to reinvigorate ontogenetically adult vegetative buds on juvenile rootstocks [11] and can be a solution for cloning adult trees of several species, in which sprouts present deficient rooting and lack of vigor [3] [4].…”