5-Azacytidine: A Promoter of Epigenetic Changes in the Quest to Improve Plant Somatic Embryogenesis

Somatic embryogenesis (SE) is a widely studied process due to its biotechnological potential to generate large quantities of plants in short time frames and from different sources of explants. The success of SE depends on many factors, such as the nature of the explant, the microenvironment generated by in vitro culture conditions, and the regulation of gene expression, among others. Epigenetics has recently been identified as an important factor influencing SE outcome. DNA methylation is one of the most studied epigenetic mechanisms due to its essential role in gene expression, and its participation in SE is crucial. DNA methylation levels can be modified through the use of drugs such as 5-Azacytidine (5-AzaC), an inhibitor of DNA methylation, which has been used during SE protocols. The balance between hypomethylation and hypermethylation seems to be the key to SE success. Here, we discuss the most prominent recent research on the role of 5-AzaC in the regulation of DNA methylation, highlighting its importance during the SE process. Also, the molecular implications that this inhibitor might have for the increase or decrease in the embryogenic potential of various explants are reviewed

Polyamines and WOX genes in the recalcitrance to plant conversion of somatic embryos of Habanero pepper (Capsicum chinense Jacq.)

In order to determine the role of polyamines in the formation and development of the somatic embryos of Capsicum chinense, the effect of different concentrations (0, 0.01, 0.1, and 1.0 mM) of Putrescine, Spermidine and Spermine on the efficiency and morphology of the embryos was evaluated. The results show that none of the three polyamines evaluated had a significant effect on the number of embryos formed, except Spermidine (1 mM), which caused a significant reduction in their numbers, in comparison with the control treatment. However, the most noteworthy result was observed in the treatment containing 0.1 mM of Spermine. The embryos developed in this treatment showed harmonic apex-radicle development, pale-green coloration and the formation of two tiny cotyledonary leaves. Real-time PCR was used to analyze the differential expression of the WUS, WOX1 and WOX3 genes in somatic embryos treated with Spermine and untreated, including the zygotic embryo. The transcript levels of the genes analyzed were found to differ significantly between both types of embryos (somatic and zygotic), with the zygotic embryos presenting a higher level of transcripts; however, compared to the untreated somatic embryos, the somatic embryos treated with Spermine showed an increase in the transcript levels of the three genes analyzed (WUS, WOX1 and WOX3); the WOX1 gene in particular presented an accumulation pattern similar to that of the zygotic embryo of the species. Keywords: Somatic embryos, zygotic embryos, polyamines, transcript patterns and morphology.

Middle Paleolithic lithic assemblages in Western Mediterranean Europe from MIS 5 to 3

This paper focuses on an overview of the sites featuring lithic industries ascribed to Middle Palaeolithic based upon a raw materials, technological organization and toolkit management. This is a synthetic analysis of the Western Mediterranean area where sites featuring broad stratigraphic sequences are abundant and enable an adequate assessment of the available record. Presenting all the data organized according to geographical regions contributed to the homogeneity of the results and allowed us to contextualize a regional synthesis, from a broad territorial and chronological point of view. This perspective was compared to other distant European spheres which in turn enabled establishing a framework that consolidates the study area as a different cluster, in- dependent from the remainder of the territories. This paper shows how the various Neanderthal populations had diverse cultural traditions throughout Europe; these are reflected by the archaeological record with the existence of diverse regional clusters that show a significant variability during the Middle Palaeolithic. Therefore it seems reasonable to conclude that even though the previously referred technical traditions persisted throughout the entire Middle Palaeolithic, arguably even more so than during more recent time periods, it seems pretty obvious that the idea of the Middle Palaeolithic being an homogenous period is wrong and should be disregarded as far as Europe and the Western Mediterranean in particular are concerned.PROMETEO/2017/060HAR2017-85153-PHAR2016-76760-C3-1-PThis paper focuses on an overview of the sites featuring lithic industries ascribed to Middle Palaeolithic based upon a raw materials, technological organization and toolkit management. This is a synthetic analysis of the Western Mediterranean area where sites featuring broad stratigraphic sequences are abundant and enable an adequate assessment of the available record. Presenting all the data organized according to geographical regions contributed to the homogeneity of the results and allowed us to contextualize a regional synthesis, from a broad territorial and chronological point of view. This perspective was compared to other distant European spheres which in turn enabled establishing a framework that consolidates the study area as a different cluster, in- dependent from the remainder of the territories. This paper shows how the various Neanderthal populations had diverse cultural traditions throughout Europe; these are reflected by the archaeological record with the existence of diverse regional clusters that show a significant variability during the Middle Palaeolithic. Therefore it seems reasonable to conclude that even though the previously referred technical traditions persisted throughout the entire Middle Palaeolithic, arguably even more so than during more recent time periods, it seems pretty obvious that the idea of the Middle Palaeolithic being an homogenous period is wrong and should be disregarded as far as Europe and the Western Mediterranean in particular are concerned