Core pathways controlling shoot meristem maintenance

Essential to the function of shoot meristems in plants to act as sites of continuous organ and tissue formation is the ability of cells within the meristem to remain undifferentiated and proliferate indefinitely. These are characteristics of the stem cells within meristems that are critical for their growth properties. Stem cells are found in tight association with the stem cell niche—those cells that signal to maintain stem cells. Shoot meristems are unique among stem cell systems in that the stem cell niche is a constantly changing population of recent daughter stem cells. Recent progress from Arabidopsis and other systems have uncovered a large number of genes with defined roles in meristem structure and maintenance. This review will focus on well‐studied pathways that represent signaling between the stem cells and the niche, that prevent ectopic differentiation of stem cells, that regulate the chromatin status of stem cell factors, and that reveal intersection of hormone signaling and meristem maintenance. WIREs Dev Biol 2013, 2:671–684. doi: 10.1002/wdev.110 For further resources related to this article, please visit the WIREs website .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99612/1/wdev110.pd

Molecular Species of Diacylglycerols and Phosphoglycerides and the Postmortem Changes in the Molecular Species of Diacylglycerols in Rat Brains

The molecular species of 1,2-diacyl- sn -glycerol (DAG), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP), and phosphatidylinositol 4,5-bisphosphate (PIP 2 ) from brains of adult rats (weighing 150 g) were determined. The DAG, isolated from brain lipid extracts by TLC, was benzoylated, and the molecular species of the purified benzoylated derivatives were separated from each other by reverse-phase HPLC. The total amount and the concentration of each species were quantified by using 1,2-distearoyl- sn -glycerol (18:0–18:0) as an internal standard. About 30 different molecular species containing different fatty acids at the sn -1 and sn -2 positions of DAG were identified in rat brains (1 min postmortem), and the predominant ones were 18:0–20:4 (35%), 16:0–18:1 (15%), 16:0–16:0 (9%), and 16:0–20:4 (8%). The molecular species of PC, PE, PS, and PI were determined by hydrolyzing the lipids with phospholipase C to DAG, which was then benzoylated and subjected to reverse-phase HPLC, PIP and PIP 2 were first dephosphorylated to PI with alkaline phosphatase before hydrolysis by phospholipase C. The molecular species composition of phosphoinositides showed predominantly the 18:0–20:4 species (50% in PI and ∼65% in PIP and PIP 2 ). PS contained mainly the 18:0–22:6 (42%) and 18:0–18:1 (24%) species. PE was mainly composed of the 18:0–20:4 (22%), 18:0–22:6 (18%), 16:0–18:1 (15%), and 18:0–18:1 (15%) species. In PC the main molecular species were 16:0–18:1 (36%), 16:0–16:0 (19%), and 18:0–18:1 (14%). Studies on postmortem brains (30 s to 30 min) showed a rapid increase in the total amount (from 40–50 nmol/g in 0 min to 210–290 nmol/g in 30 min) and in all the molecular species of DAG. Comparatively larger increases (seven- to 10-fold) were found for the 18:0–20:4 and 16:0–20:4 species. Comparison of DAG species with the molecular species of different glycerolipids indicated that the rapid postmortem increase in content of DAG was mainly due to the breakdown of phosphoinositides. However, a slow but continuous breakdown of PC to DAG was also observed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66196/1/j.1471-4159.1991.tb08161.x.pd

A WUSCHEL-Independent Stem Cell Specification Pathway is Repressed by PHB, PHV and CNA in Arabidopsis.

A tight balance between stem cell specification and differentiation is important to maintain a functional meristem and continuously initiate new organs throughout the lifespan of plants. The Arabidopsis WUSCHEL (WUS) transcription factor has been thought to be essential for specification of stem cell identity at shoot and flower meristems. CLAVATA (CLV) signaling acts through POL/PLL1 to limit WUS transcription and thus promote stem cell differentiation. To further dissect the CLV signaling pathway, I performed a modifier mutagenesis on pol-6 seeds and identified a novel allele of AGO10 (ago10-15). AGO10 prevents the degradation the HD-zip III family of transcription factors. I used a triple mutant of three of the HD-zip III members (PHB, PHV and CNA) which have superficially been described as having post-embryonic meristem enhancement. I found that phb phv cna mutants accumulate stem cells at both the shoot and flower meristems, along with changes to CLV3 and WUS cis element activation. When I generated the clv3 phb phv cna quadruple mutant, I observed dramatic enhancement of the clv stem cell accumulation phenotypes at the shoot and flower meristem. Remarkably, wus phb phv cna quadruple mutants developed functional meristems despite the absence of the central stem cell factor WUS. This conclusion is based on the ability of the triple mutant to engage in continuous organogenesis, the formation of meristem-like structures, as well as the retention of cell layering and WUS cis element activation within these meristem-like structures. These observations allow for a number of conclusions. First, WUS is dispensable for shoot meristem formation and organogenesis. Second, PHB/PHV/CNA represent a second, previously unknown, pathway for stem cell specification at shoot and flower meristems. Third, PHB/PHV/CNA act to repress this novel stem cell specification. When de-repressed, this second stem cell pathway leads to an accumulation of stem cells and an enlargement of the stem cell niche. When de-repressed in a wus mutant background, this second stem cell pathway leads to functional meristems. These results indicate a set of key stem cell specification factors remains unidentified.PHDMolecular, Cellular and Developmental BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107112/1/bluelee_1.pd

Attention mechanisms and emotion judgment for Korean and American emotional faces: an eye movement study

IntroductionThis study investigates attention mechanisms and the accuracy of emotion judgment among South Korean children by employing Korean and American faces in conjunction with eye-tracking technology.MethodsA total of 42 participants were individually presented with photos featuring either Korean or American children, and their task was to judge the emotions conveyed through the facial expressions in each photo. The participants’ eye movements during picture viewing were meticulously observed using an eye tracker.ResultsThe analysis of the emotion judgment task outcomes revealed that the accuracy scores for discerning emotions of joy, sadness, and anger in Korean emotional faces were found to be significantly higher than those for American children. Conversely, no significant difference in accuracy scores was observed for the recognition of fear emotion between Korean and American faces. Notably, the study also uncovered distinct patterns of fixation duration among children, depending on whether they were viewing Korean or American faces. These patterns predominantly manifested in the three main facial areas of interest, namely the eyes, nose, and mouth.DiscussionThe observed phenomena can be best understood within the framework of the “other-race effect.” Consequently, this prototype formation leads to heightened accuracy in recognizing and interpreting emotional expressions exhibited by faces belonging to the same racial group. The present study contributes to a deeper understanding of how attention mechanisms and other-race effects impact emotion judgment among South Korean children. The utilization of eye-tracking technology enhances the validity and precision of our findings, providing valuable insights for both theoretical models of face processing and practical applications in various fields such as psychology, education, and intercultural communication

Systematic identification and integrative analysis of novel genes expressed specifically or predominantly in mouse epididymis

BACKGROUND: Maturation of spermatozoa, including development of motility and the ability to fertilize the oocyte, occurs during transit through the microenvironment of the epididymis. Comprehensive understanding of sperm maturation requires identification and characterization of unique genes expressed in the epididymis. RESULTS: We systematically identified 32 novel genes with epididymis-specific or -predominant expression in the mouse epididymis UniGene library, containing 1505 gene-oriented transcript clusters, by in silico and in vitro analyses. The Northern blot analysis revealed various characteristics of the genes at the transcript level, such as expression level, size and the presence of isoform. We found that expression of the half of the genes is regulated by androgens. Further expression analyses demonstrated that the novel genes are region-specific and developmentally regulated. Computational analysis showed that 15 of the genes lack human orthologues, suggesting their implication in male reproduction unique to the mouse. A number of the novel genes are putative epididymal protease inhibitors or β-defensins. We also found that six of the genes have secretory activity, indicating that they may interact with sperm and have functional roles in sperm maturation. CONCLUSION: We identified and characterized 32 novel epididymis-specific or -predominant genes by an integrative approach. Our study is unique in the aspect of systematic identification of novel epididymal genes and should be a firm basis for future investigation into molecular mechanisms underlying sperm maturation in the epididymis

Development of a Mobile Application, “Wild Flowers of Bukhansan National Park (version 1.0)”, for Identification of Plants in Bukhansan National Park

AbstractWe developed the educational purpose mobile application, named “Wild Flowers of Bukhansan National Park (version 1.0)”, aiming for easy identification of wildflowers for students and visitors in the park. When visitors find a flower or part of plant in the park, visitors can search for its name utilizing the pictures and characters provided in their own smartphone mobile devices or tablet PCs. The application provides pictures of wildflowers in the park and character-based searching system based on 12 diagnostic features (e.g., growth form, leaf arrangement, flower symmetry, petal color, petal number, sepal number, etc). We adopted the complete floristic survey of Chung and Lee (1962) and added species that we confirmed their distribution in the park during the development of this application. In summary, number of vascular plants in this park was estimated to be 428 taxa including 100 families, 280 genera, 327 species, 1 subspecies, 50 varieties, and 5 formas. We provided a total of 588 pictures representing 358 taxa and each taxon includes multiple pictures in many cases. Included identification quizzes can be an efficient educational tool as well as fun activity for students and visitors who are learning plant species in Korea. Our next step will include GPS function in the application for indicating visitor's location and for providing previously reported sites of the species that we interested in the map of the park. The future application which includes GPS function will be a valuable tool for the monitoring of rare plants, plant researches related to the climate changes, etc. We currently provide Korean iPhone version only, and English version and both of android versions will be serviced soon

Integrative characterization of germ cell-specific genes from mouse spermatocyte UniGene library

<p>Abstract</p> <p>Background</p> <p>The primary regulator of spermatogenesis, a highly ordered and tightly regulated developmental process, is an intrinsic genetic program involving male germ cell-specific genes.</p> <p>Results</p> <p>We analyzed the mouse spermatocyte UniGene library containing 2155 gene-oriented transcript clusters. We predict that 11% of these genes are testis-specific and systematically identified 24 authentic genes specifically and abundantly expressed in the testis via in <it>silico </it>and <it>in vitro </it>approaches. Northern blot analysis disclosed various transcript characteristics, such as expression level, size and the presence of isoform. Expression analysis revealed developmentally regulated and stage-specific expression patterns in all of the genes. We further analyzed the genes at the protein and cellular levels. Transfection assays performed using GC-2 cells provided information on the cellular characteristics of the gene products. In addition, antibodies were generated against proteins encoded by some of the genes to facilitate their identification and characterization in spermatogenic cells and sperm. Our data suggest that a number of the gene products are implicated in transcriptional regulation, nuclear integrity, sperm structure and motility, and fertilization. In particular, we found for the first time that Mm.333010, predicted to contain a trypsin-like serine protease domain, is a sperm acrosomal protein.</p> <p>Conclusion</p> <p>We identify 24 authentic genes with spermatogenic cell-specific expression, and provide comprehensive information about the genes. Our findings establish a new basis for future investigation into molecular mechanisms underlying male reproduction.</p

The origins and metabolism of diacylglycerol and phosphatidate formed upon stimulation of neural receptors.

1,2-diacyl-sn-glycerol (DAG), besides being a biosynthetic precursor of glycerolipids, has recently been shown to act as a second messenger activating protein kinase C (PKC). The sources and metabolism of both this second messenger DAG and the phosphatidate (PA) formed upon inositide-linked receptor stimulation were studied. DAG isolated from biological samples was benzoylated and the molecular species of the benzoylated DAG's were separated from each other by reverse-phase high-performance liquid chromatography. The total mass and the masses of individual molecular species were quantified by using an internal standard. Molecular species of all the phosphoglycerides were also analyzed after being hydrolyzed into DAG. About thirty different molecular species were identified in resting rat brains (45 nmol of total DAG/g brain). Studies on postmortem changes of brain DAG showed that the initial ($$1 min) they originated both from PI's (30-15%) and PC (70-85%). The molecular species profile of the incremental PA (200% over control) was very similar to that of PI's. When cells were preincubated with staurosporine, a PKC inhibitor, CCh produced DAG only from PI's. In contrast, 1-oleoyl-2-acetyl glycerol, a PKC activator, generated DAG solely from hydrolysis of PC. From these studies in neuroblastoma cells, it was concluded that DAG generated from PI's activates PKC and is recycled back to PI's via PA. The activated PKC stimulates PC-specific phospholipase C causing the breakdown of PC to DAG, which in turn may activate other kinds of PKC resulting in long-term effects. PC-specific phospholipase D is not stimulated after receptor activation and DAG produced from PC is not phosphorylated to PA.Ph.D.Biological ChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/105936/1/9226950.pdfDescription of 9226950.pdf : Restricted to UM users only

Quantitative Analysis of Changes in the Molecular Species of Glycerolipids in Cultured Cells during Signal Transduction

A method for the quantitative analysis of the molecular species of glycerolipids present In biological samples has been described. 1,2-Diacyl-sn-glycerol, either isolated from biological samples or enzymatically generated from phosphoglycerides, is benzoylated at the sn-3 position and then subjected to reverse-phase (C18-silica) HPLC to separate the molecular species of different hydrophobicitles. An internal standard (1,2-distearoyl-sn-glycerol) is used to identify and quantify the various species eluted from the reverse-phase column. Examples are given for the quantitative analysis of molecular species and precursor-product relationships of glycerolipids generated In SK-N-SH neuroblastoma cells after stimulation of the cell-surface muscarinic acetylcholine receptors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30528/1/0000160.pd