Female parthenogenetic apomixis and androsporogenetic parthenogenesis in embryonal cells of Araucaria angustifolia: interpolation of progenesis and asexual heterospory in an artificial sporangium.

Cell fate, development timing and occurrence of reproductive versus apomictic development in gymnosperms are shown to be influenced by culture conditions in vitro. In this study, female parthenogenetic apomixis (fPA), androsporogenetic parthenogenesis (mAP) and progenesis were demonstrated using embryonal initials of Araucaria angustifolia in scaled-up cell suspensions passing through a single-cell bottleneck in darkness and in an artificial sporangium (AS). Expression was based on defined nutrition, hormones and feedforward-adaptive feedback process controls at 23-25 °C and in darkness. In fPA, the nucleus of an embryonal initial undergoes endomitosis and amitosis, forming a diploid egg-equivalent and an apoptotic ventral canal nucleus in a transdifferentiated archegonial tube. Discharge of egg-equivalent cells as parthenospores and their dispersal into the aqueous culture medium were followed by free-nuclear conifer-type proembryogenesis. This replaced the plesiomorphic and central features of proembryogenesis in Araucariaceae. Protoplasmic fusions of embryonal initials were used to reconstruct heterokaryotic expressions of fPA in multiwell plates. In mAP, restitutional meiosis (automixis) was responsible for androsporogenesis and the discharge of monads, dyads, tetrads and polyads. In a display of progenesis, reproductive development was brought to an earlier ontogenetic stage and expressed by embryonal initials. Colchicine increased polyploidy, but androspore formation became aberrant and fragmented. Aberrant automixis led to the formation of chromosomal bouquets, which contributed to genomic silencing in embryonal initials, cytomixis and the formation of pycnotic micronucleated cells. Dispersal of female and male parthenospores displayed heteromorphic asexual heterospory in an aqueous environment.

Female parthenogenetic apomixis and androsporogenesis in Douglas-fir embryonal initials in an artificial sporangium.

Control of female parthenogenetic apomixis and androsporogenesis of Douglas-fir embryonal initials was studied using an experimental culture system in which changes in growth condition can mediate changes in cell identity and outcomes. This culture system constitutes an artificial sporangium in which myriad culture conditions can be simulated and should be applicable for research on a variety of gymnosperms. In this study, embryonal initials from developing seeds from two Douglas-fir trees were rescued and became reprogrammed for female parthenogenetic apomixis (fPA) and parthenogenetic androsporogenesis (mPA). Female PA was initiated by endomitosis forming a binucleate cell with a diploid egg-equivalent and an apoptotic ventral canal nucleus in an archegonial tube. Egg-equivalent nuclei formed cells (parthenotes) that were discharged into an aqueous culture medium. Parthenotes developed axial tiers atypical of early embryogenesis in seeds. Earlier in the year, androsporangial tubes were parthenogenetically differentiated and released monads, dyads, triads, and tetrads into the culture medium. Spores showed chromosomal aberrations. PA demonstrated a temporal separation in gender expression (dichogamy). Embryonal initials brought forward and by-passed the long juvenile phases normally needed for cells to develop into trees and express reproductive maturity. Expressions of fPA and mPA indicated that the specialized culture flasks served as an artificial sporangium (AS). Awareness is raised for the value of an AS for research in gymnosperm life cycles and as a teaching and research laboratory.

Salmine and the homeotic integrity of early embryos of Norway spruce.

Salmine, an arginine-rich protamine, is explored for its concentration-dependent potential to restructure the genome and remodel the homeotic development of Norway spruce embryos expressing monozygotic cleavage polyembryony (MCP). In controls and at low salmine, two protein fractions on SDS-PAGE gels were associated with cells responsible for generating the basal plan for early embryogenesis. With high salmine, embryonal initials no longer differentiated into embryonal tubes. Embryos having embryonal tubes no longer enucleated and differentiated into embryonal suspensors. Biomass and amino acid N declined. Nuclear and cytoplasmic organization was disrupted and nucleoli were highly vacuolated. The transcription of the two protein fractions, PCNA (cyclin) activity and MCP were blocked. Cellular proteins were turned over by proteasomal ubiquitination and others released into the culture medium. Biomass loss and gluconeogenesis of amino acids led to the accumulation of free arginine N. No evidence was obtained with salmine for the remodeling of cells into gametes.

Arginine, scurvy and Cartier's "tree of life".

Several conifers have been considered as candidates for "Annedda", which was the source for a miraculous cure for scurvy in Jacques Cartier's critically ill crew in 1536. Vitamin C was responsible for the cure of scurvy and was obtained as an Iroquois decoction from the bark and leaves from this "tree of life", now commonly referred to as arborvitae. Based on seasonal and diurnal amino acid analyses of candidate "trees of life", high levels of arginine, proline, and guanidino compounds were also probably present in decoctions prepared in the severe winter. The semi-essential arginine, proline and all the essential amino acids, would have provided additional nutritional benefits for the rapid recovery from scurvy by vitamin C when food supply was limited. The value of arginine, especially in the recovery of the critically ill sailors, is postulated as a source of nitric oxide, and the arginine-derived guanidino compounds as controlling factors for the activities of different nitric oxide synthases. This review provides further insights into the use of the candidate "trees of life" by indigenous peoples in eastern Canada. It raises hypotheses on the nutritional and synergistic roles of arginine, its metabolites, and other biofactors complementing the role of vitamin C especially in treating Cartier's critically ill sailors.

Monozygotic cleavage polyembryogenesis and conifer tree improvement.

The mass cloning of elite genotypes of commercially important conifers has led to the establishment of an industrial forest of two of the most important softwood species in the USA. Embryonal-suspensor masses, produced by monozygotic cleavage polyembryony (MCP), are rescued from controlled-pollinated seeds in tree breeding orchards. MCP is scaled up as cell suspensions and grown into mature somatic embryos. The embryos serve as a source for the production of various artificial and manufactured seeds used in replicated field trials to test genotype x environmental interactions. For the capture of genetic gains, early selections are based on correlations with known traits. This reduces the costs of years of tree improvement. Mass cloning and genotype cryopreservation enables field testing under a wider range of sites. Process-controlled bioreactors are proposed as artificial ovules to impose nutritional variables from the mother tree, and to simulate environmental factors that are known to affect the performance of the new generation. Comparisons among extant and modern conifer genotypes would provide new insights regarding their latent potentials for apomixis, the alternation of generations, and adaptive plasticity.