Somatic embryogenesis is the process by which somatic cells, under induction conditions, generate embryogenic cells, which go through a series of morphological and biochemical changes that result in ...the formation of a somatic embryo. Somatic embryogenesis differs from zygotic embryogenesis in that it is observable, its various culture conditions can be controlled, and a lack of material is not a limiting factor for experimentation. These characteristics have converted somatic embryogenesis into a model system for the study of morphological, physiological, molecular and biochemical events occurring during the onset and development of embryogenesis in higher plants; it also has potential biotechnological applications. The focus of this review is on embryo development through somatic embryogenesis and especially the factors affecting cell and embryo differentiation.
Auxins are responsible for a large part of the plant development process. To exert their action, they must move throughout the plant and from cell to cell, which is why plants have developed complex ...transport systems for indole-3-acetic acid (IAA). These transporters involve proteins that transport IAA into cells, transporters that move IAA to or from different organelles, mainly the endoplasmic reticulum, and transporters that move IAA out of the cell. This research determined that
has 12 PIN transporters in its genome. The twelve transporters are expressed during different stages of development in
zygotic embryos. Using different bioinformatics tools, we determined the type of transporter of each of the
PIN proteins and their structure and possible location in the cell. We also predict the potential phosphorylation sites for each of the twelve-PIN proteins. The data show the presence of highly conserved sites for phosphorylation and those sites involved in the interaction with the IAA.
Background and Aims In Costa Rica, coffee (Coffea arabica) plants are often grown in agroforests. However, it is not known if shade-inducing trees reduce coffee plant biomass through root ...competition, and hence alter overall net primary productivity (NPP). We estimated biomass and NPP at the stand level, taking into account deep roots and the position of plants with regard to trees. Methods Stem growth and root biomass, turnover and decomposition were measured in mixed coffee/tree (Erythrina poeppigiana) plantations. Growth ring width and number at the stem base were estimated along with stem basal area on a range of plant sizes. Root biomass and fine root density were measured in trenches to a depth of 4 m. To take into account the below-ground heterogeneity of the agroforestry system, fine root turnover was measured by sequential soil coring (to a depth of 30 cm) over 1 year and at different locations (in full sun or under trees and in rows/inter-rows). Allometric relationships were used to calculate NPP of perennial components, which was then scaled up to the stand level. Key Results Annual ring width at the stem base increased up to 2·5 mm yr-1 with plant age (over a 44-year period). Nearly all (92 %) coffee root biomass was located in the top 1·5 m, and only 8 % from 1·5 m to a depth of 4 m. Perennial woody root biomass was 16 t ha-1 and NPP of perennial roots was 1·3 t ha-1 yr-1. Fine root biomass (0-30 cm) was two-fold higher in the row compared with between rows. Fine root biomass was 2·29 t ha-1 (12 % of total root biomass) and NPP of fine roots was 2·96 t ha-1 yr-1 (69 % of total root NPP). Fine root turnover was 1·3 yr-1 and lifespan was 0·8 years. Conclusions Coffee root systems comprised 49 % of the total plant biomass; such a high ratio is possibly a consequence of shoot pruning. There was no significant effect of trees on coffee fine root biomass, suggesting that coffee root systems are very competitive in the topsoil.
Gene expression in response to signaling molecules has been well studied in the leaves of the model plant species Arabidopsis thaliana. However, knowledge of gene expression and metabolic regulation ...at the root level is limited. Here, the signaling compounds salicylic acid (SA), methyl jasmonate (MeJA) and nitric oxide (NO) were applied exogenously to induce various defense responses in roots, and their effect was studied using a combination of genomic, molecular and biochemical approaches. Genes involved in defense signaling/activation, cellular redox state, metabolism, transcription factors and membrane transport were altered in expression following treatment with SA, MeJA and NO. In addition, it was found that SA-, MeJA- and NO-elicited roots increased the root exudation of phytochemicals compared with the roots of nontreated control plants. Transport systems likely to be involved in the root exudation of phytochemicals, including the MATE, ABC, MFS, amino acid, sugar and inorganic solute transporters, showed altered expression profiles in response to treatments. Overall, significant differences were found in the signaling compound-elicited expression profiles of genes in roots vs those in leaves. These differences could be correlated to the underground nature of roots and their exposure to higher microbial inoculum rates under natural conditions.
Bacterial infections are an important threat in the early post–liver transplantation period. Donor‐transmitted infections, although rare, can have high mortality. The utility of routine culture from ...the donor bile duct as screening of donor‐transmitted infection has not been evaluated. We performed a retrospective study of 200 consecutive liver transplants between 2010 and 2015. Demographic, clinical, and microbiological data were collected from the recipients’ medical records. Clinical data included pretransplantation, perioperative, and posttransplantation information (until 30 days after the procedure). The 3‐month patient survival and/or retransplantation were recorded. A total of 157 samples from the donor bile duct were collected and cultured. Only 8 were positive. The microorganisms isolated were as follows: Klebsiella pneumoniae, n = 2; Escherichia coli, n = 1; Enterobacter cloacae, n = 1; Streptococcus anginosus, n = 1; Streptococcus sp., n = 1; multiple gram‐negative bacilli, n = 1; and polymicrobial, n = 1. All of the microorganisms were susceptible to the antibiotic prophylaxis administered. During the first month after transplantation, 81 recipients developed 131 infections. Only 1 of these recipients had a donor with a positive bile culture, and none of the infections were due to the microorganism isolated in the donor’s bile. The 3‐month overall survival was 89.5%, and there were no differences between recipients with positive donor bile cultures and those with negative donor bile cultures (87.5% versus 89.26%; P > 0.99). Routine testing of donor bile cultures does not predict recipients’ infection or survival after liver transplantation and should not be recommended.
Species delimitation studies based on integrative taxonomic approaches have received considerable attention in the last few years, and have provided the strongest hypotheses of species boundaries. We ...used three lines of evidence (molecular, morphological, and niche envelopes) to test for species boundaries in Peruvian populations of the Liolaemus walkeri complex. Our results show that different lines of evidence and analyses are congruent in different combinations, for unambiguous delimitation of three lineages that were "hidden" within known species, and now deserve species status. Our phylogenetic analysis shows that L. walkeri, L. tacnae and the three new species are strongly separated from other species assigned to the alticolor-bibronii group. Few conventional morphological characters distinguish the new species from closely related taxa and this highlights the need to integrate other sources of data to erect strong hypothesis of species limits. A taxonomic key for known Peruvian species of the subgenus Lioalemus is provided.
Auxin and polar auxin transport have been implicated in controlling zygotic embryo development, but less is known about their role in the development of somatic embryos. The aim of this study was to ...determine if indole-3-acetic acid (IAA) and the PIN1 transporter participate in the induction of somatic embryogenesis (SE) and the development of somatic embryos. The results show that IAA levels gradually increase during pre-treatment and accumulate in the chloroplast. During pre-treatment and the globular stage of SE in
C. canephora
, auxin is distributed uniformly in all of the cells of the somatic embryo. During the subsequent stages of development, auxins are mobilized to the cells that will form the cotyledons and the root meristem. The location of the PIN transporters shifts from the plasmalemma of the protoderm cells during the globular stage to the plasmalemma of the cells that will give rise to the cotyledons and the vascular tissue in the late stages of somatic embryogenesis. The incubation of the explants in the presence of 2,3,5-triiodobenzoic acid (TIBA) produced aberrant somatic embryos, suggesting that PIN1 mediates the transport of IAA.
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