Terminal Buds Research Articles

Biochemical changes in terminal buds of three different walnut (Juglans regia L.) genotypes during dormancy break

To the better management of frostbite problem in fruit crops, evaluation of biochemical changes in buds during dormancy break is a key factor. In this study biochemical changes in terminal buds of three different walnut genotypes (early-season, mid-season, and late-season), was investigated during winter dormancy release time. Terminal bud samples were taken from the genotypes in two different times in winter (1st and 20th of March). Variables such as; bud soluble sugars, starch, proline, chlorophyll, total phenolic and protein content as well as catalase (CAT) and guaiacol peroxidase (GPO) enzymes activities were assessed. Analysis of variance ANOVA) revealed significant differences (p ≤ 0.05) for the measured variables and sampling times among the genotypes. The results indicated that the late growth genotype had the highest content of soluble sugars and proline, and the lowest amount of starch and protein (p ≤ 0.05) in comparison with early and mid-season growth genotypes. Different enzymes activities were observed in terminal buds among the genotypes. As sampling time delaying, the content of chlorophyll, CAT and GPO enzymes activity increased, while a decrease in proline and total phenol was observed. The results of this study can be considered to a better understanding of the primary mechanisms of bud dormancy break in walnut to reduce the late spring frost damage problem as well as for using in breeding programs.

BUD FERTILITY OF NEW TABLE GRAPE CULTIVARS AND BREEDING SELECTIONS IN THE SÃO FRANCISCO VALLEY

ABSTRACT Knowledge of bud fertility is an important aid in selection of new cultivars of table grapes with high yield potential. The aim of this study was to determine the sprouting percentage and fertility index of buds of 11 cultivars and table grape breeding selections over five production cycles. The study was carried out at the Bebedouro Experimental Field of Embrapa Semiárido in Petrolina-PE, Brazil, in the period 2013-2015 considering 14 table grape genotypes and 5 production cycles as sources of variation. A randomized block experimental design was used, evaluating sprouting percentage and the mean bud fertility index. A significant effect of the genotype on sprouting was observed only in the first and second production cycles; however, bud fertility exhibited significant interaction between the genotype and the production cycle, and the highest mean values of bud fertility were obtained in the fifth cycle in the 2nd semester of 2015. The cultivars ‘A Dona’, ‘A1105’, ‘BRS Clara’, and Marroo Seedless’ stood out through high bud fertility (mean values from 0.78 to 0.95 bunches/shoot) in all the cycles evaluated, with higher values in the terminal buds of the cane (8th and 9th buds). These results show the yield potential of these new cultivars in the São Francisco Valley region.

Photoperiodic Regulation of Growth-Dormancy Cycling through Induction of Multiple Bud-Shoot Barriers Preventing Water Transport into the Winter Buds of Norway Spruce.

Whereas long days (LDs) sustain shoot elongation, short days (SDs) induce growth cessation and formation of dormant buds in young individuals of a wide range of temperate and boreal tree species. In specific conifers, including Norway spruce, photoperiodic control of bud development is associated with the formation of a plate of thick-walled cells, denoted as the crown, at the base of the bud. Information about cellular characteristics of this crown region is limited. We aimed to test whether the crown region is an important SD-induced barrier ensuring dehydration of the developing winter bud by preventing water influx. Using microscopy and synchrotron techniques, we show here that under LD, cell walls in growing shoot tips had highly methyl-esterified homogalacturonan pectin. During SD-induced bud development, the homogalacturonan in the crown region was de-methyl-esterified, enabling Ca2+ binding and crosslinking, a process known to decrease cell wall water permeability by reducing pectin pore size. In addition, there was abundant callose deposition at plasmodesmata in the crown region, and xylem connections between the bud and the subtending shoot were blocked. Consistent with reduced water transport across the crown region into the bud, uptake of fluorescein in shoot tips was blocked at the base of the bud under SD. Upon transfer from SD to bud-break-inducing LD, these processes were reversed, and aquaporin transcript levels significantly increased in young stem tissue after 4 weeks under LD. These findings indicate that terminal bud development is associated with reduced water transport through decreased cell wall permeability and blocking of plasmodesmata and xylem connections in the crown structure. This provides further understanding of the regulatory mechanism for growth-dormancy cycling in coniferous tree species such as Norway spruce.

Proteomics reveals key proteins participating in growth difference between fall dormant and non-dormant alfalfa in terminal buds

To explore the molecular mechanism of growth differences between fall dormant (FD) and non-FD alfalfa, we conducted iTRAQ-based quantitative proteomics on terminal buds of Maverick (FD) and Cuf101 (non-FD) cultivars, identified differential abundance protein species (DAPS) and verified expression profiling of certain corresponding mRNA by qRT-PCR. A total of 3872 protein species were annotated. Of the 90 DAPS, 56 and 34 were respectively up- and down-accumulated in Maverick, compared to Cuf101. They were grouped into 35 functional categories and enriched in seven pathways. Of which, auxin polar transport was up-regulated, while phenylpropanoid biosynthesis, pyruvate metabolism and transportation, vitamin B1 synthesis process and flavonoid biosynthesis were down-regulated in Maverick, comparing with Cuf101. In Maverick, mRNA abundances of l-asparaginase, chalcone and stilbene synthase family protein, cinnamyl alcohol dehydrogenase-like protein, thiazole biosynthetic enzyme, pyruvate dehydrogenase E1 beta subunit, and aldo/keto reductase family oxidoreductase were significantly lower at FD than at other stages, and lower than in Cuf101. We also observed opposite mRNA profiles of thiazole biosynthetic enzyme, chalcone and stilbene synthase family protein, pyruvate dehydrogenase E1 beta subunit in both cultivars from summer to autumn. Our results suggest that these DAPS could play important roles in growth difference between FD and non-FD alfalfa. Biological significanceUp to now, as far as we know, currently the proteins related with the growth differences between FD and non-FD alfalfa cultivars in autumn have not yet been identified in terminal buds. This study identified the protein species expressed in alfalfa terminal buds, selected differentially abundant protein species in terminal buds between Maverick (FD) and Cuf101 (non-FD) cultivars in autumn and identified the important protein species participated in the growth differences. This study lays a foundation for further investigation of the molecular mechanism of the growth differences between FD and non-FD alfalfa and the cultivation of advanced alfalfa cultivars.

Persian Walnut Phenology: Effect of Chilling and Heat Requirements on Budbreak and Flowering Date

Walnut production is limited by late-spring frost in many countries. The current research was carried out to evaluate chilling and heat requirement of catkin and terminal buds break on six selected superior walnut genotypes and cultivars (‘C-25’, ‘88-1’, ‘88-2’, ‘Chandler’, ‘Jamal’ and ‘Damavand’). The Utah and accumulation growing degree hours (GDH) models were applied to determine the chilling and heat requirements under field and greenhouse conditions, respectively. ‘Damavand’ cultivar (650 CU) and ‘C-25’ genotype (650-800 CU) had the lowest chilling requirement for terminal bud break. ‘Jamal’ cultivar and ‘C-25’ genotypes had the lowest chilling requirement to break the dormancy of catkins (650–800 CU). ‘Chandler’ cultivar and ‘88-1’ and ‘88-2’ genotypes as late-leafing genotypes/cultivars had the highest chilling and heat requirements to break dormancy of terminal buds (800-1100 CU and 11832-12648 GDH) and catkin (800-950 CU and 11484-12180 GDH). In conclusion, late-leafing genotypes/cultivars had the higher heat requirement than early-leafing genotypes/cultivars. Based on the results, a linear and significant relation was observed between chilling requirement and heat accumulation. Therefore, heat accumulation of buds and catkins was reduced by increase in the amount of chilling requirement. Furthermore, the result revealed that heat accumulation is more important than chilling requirements to estimate walnut budbreak date. The GDH of catkins and terminal buds was decreased with increase in the average temperature during heat accumulation.

Immunolocalization patterns of cytokeratins during salivary acinar cell development in mice.

Embryonic development of the mouse salivary glands begins with epithelial thickening and continues with sequential changes from the pre-bud to terminal bud stages. After birth, morphogenesis proceeds, and the glands develop into a highly branched epithelial structure that terminates with saliva-producing acinar cells at the adult stage. Acinar cells derived from the epithelium are differentiated into serous, mucous, and seromucous types. During differentiation, cytokeratins, intermediate filaments found in most epithelial cells, play vital roles. Although the localization patterns and developmental roles of cytokeratins in different epithelial organs, including the mammary glands, circumvallate papilla, and sweat glands, have been well studied, their stage-specific localization and morphogenetic roles during salivary gland development have yet to be elucidated. Therefore, the aim of this study was to determine the stage and acinar cell type-specific localization pattern of cytokeratins 4, 5, 7, 8, 13, 14, 18, and 19 in the major salivary glands (submandibular, sublingual, and parotid glands) of the mouse at the E15.5, PN0, PN10, and adult stages. In addition, cell physiology, including cell proliferation, was examined during development via immunostaining for Ki67 to understand the cellular mechanisms that govern acinar cell differentiation during salivary gland morphogenesis. The distinct localization patterns of cytokeratins in conjunction with cell physiology will reveal the roles of epithelial cells in salivary gland formation during the differentiation of serous, mucous or seromucous salivary glands.

The development of lingual glands in the domestic duck (Anas platyrhynchos f. domestica): 3D-reconstruction, LM, and SEM study.

The major salivary glands of birds develop by branching or elongation of the epithelial cords. The development of the minor salivary glands in form of the lingual glands has never been described. Among birds, only Anatidae have three types of the lingual glands: rostral, caudo-lateral, and caudo-medial lingual glands. The study aims to characterize the manner and rate of the lingual glands development in the domestic duck and their topographical arrangement relative to the hyoid apparatus. The study reveals that all three types of the lingual glands develop by branching. We describe five stages of the lingual glands development in the domestic ducks: prebud, initial bud, pseudoglandular, canalicular, and terminal bud stage. The pattern of the lingual glands development in birds is similar to that described for mammals, with the exception, that the terminal buds are formed at the same time as the lumen of the glands. Generally, the rostral lingual gland starts to branch earlier than the caudal lingual glands. The 3D-reconstruction shows the location and direction of lingual gland development relative to the entoglossal cartilage and basibranchial bone. Light microscopy and scanning electron microscopy allow to characterize the histogenesis of the embryonic epithelium into glandular epithelium. At a time of hatching only secretory units of caudal lingual glands resemble the secretory units of the adult domestic duck. The rostral and caudo-lateral lingual glands are arranged on the sides of the entoglossal cartilage and basibranchial bone and caudo-madial lingual glands are located over the basibranchial bone. We suggest that such an arrangement of the lingual glands in the domestic duck is important during food intake and responsible for reduction of friction and formation of food bites.

Mango malformation in South Africa: occurrence of conidia of Fusarium mangiferae on malformed panicles and leaves

Mango malformation caused by Fusarium mangiferae is a serious disease in South Africa, causing severe economic losses annually. The aim of this study was to determine the occurrence of conidia of F. mangiferae on malformed panicles and leaves in a 'Sensation' mango orchard at the Agricultural Research Council's Institute for Tropical and Subtropical Crops (ARC-ITSC) in Nelspruit, Mpumalanga, South Africa, in order to optimise disease control. Malformed panicles and leaves were collected weekly during 2013 and 2014, spores washed off from panicles and leaves respectively and plated onto a semi-selective medium for Fusarium to determine spore concentrations. The average number of conidia per gram panicles and gram leaves were calculated for each sampling date. Results showed that low levels of conidia were detected on malformed panicles in the first three months of flowering (July to September). Spore numbers increased slowly through the following month (October), jumped dramatically the next month (November) and decreased thereafter. An increase in conidial number coincided with drying out of individual flowers on the malformed panicles. The presence of spores on the leaves coincided with the detection of high numbers of spores on malformed panicles. This is also the time when infection of terminal buds takes place. Spraying of fungicides should be focused on when inoculum is available to keep inoculum levels as low as possible and to protect the terminal buds from infection.

WNT-Mediated Regulation of FOXO1 Constitutes a Critical Axis Maintaining Pubertal Mammary Stem Cell Homeostasis

Puberty is characterized by dynamic tissue remodeling in the mammary gland involving ductal elongation, resolution into the mature epithelial bilayer, and lumen formation. To decipher the cellular mechanisms underlying these processes, we studied the fate of putative stem cells, termed cap cells, present in terminal end buds of pubertal mice. Employing a p63CreERT2-based lineage-tracing strategy, we identified a unipotent fate for proliferative cap cells that only generated cells with basal features. Furthermore, we observed that dislocated "cap-in-body" cells underwent apoptosis, which aided lumen formation during ductal development. Basal lineage-specific profiling and genetic loss-of-function experiments revealed a critical role for FOXO transcription factors in mediating these proliferative versus apoptotic fates. Importantly, these studies revealed a mode of WNT signaling-mediated FOXO1 inhibition, potentially mediated through AKT. Together, these data suggest that the WNT pathway confers proliferative and survival advantages on cap cells via regulation of FOXO1 localization.

Variation of inflorescence character in response to GA3application at advancing stages of terminal floral bud differentiation in mango

Variation of inflorescence character in response to GA₃application at advancing stages of terminal floral bud differentiation in mango

The dioecious Populus tremula displays interactive effects of temperature and ultraviolet-B along a natural gradient

Observed and projected warming has provoked research interest on tree phenology in relation to climate. While both ultraviolet-B (UV-B) radiation and warming has been shown to affect growth and development in plants, the combined effects of the two environmental factors has been little studied. In addition, there is concern for environmental change yielding divergent responses between sexes in dioecious tree species. Here, we present a study of the dioecious Populus tremula grown along a natural temperature and UV-B gradient in Central Norway, reducing UV-B using specific screening filters. We tested for effects on growth, timing of terminal bud formation and bud break, carbon and nitrogen content and concentrations of phenolic compounds. Increased elevation had a negative effect on plant growth and promoted bud formation, with effects differing between plant sexes. UV-B attenuation delayed bud formation and enhanced growth of males at the highest elevation, counteracting the effect of low temperature. In addition, elevation and UV-B affected concentrations of different phenolics in stems and leaves. Our data show that interactive effects of warming and other climate factors like UV-B should be considered when predicting climate change effects in woody plants, and add to present evidence of sex-related responses to climate change in dioecious woody plants.

Epithelial Markers aSMA, Krt14, and Krt19 Unveil Elements of Murine Lacrimal Gland Morphogenesis and Maturation.

As an element of the lacrimal apparatus, the lacrimal gland (LG) produces the aqueous part of the tear film, which protects the eye surface. Therefore, a defective LG can lead to serious eyesight impairment. Up to now, little is known about LG morphogenesis and subsequent maturation. In this study, we delineated elements of the cellular and molecular events involved in LG formation by using three epithelial markers, namely aSMA, Krt14, and Krt19. While aSMA marked a restricted epithelial population of the terminal end buds (TEBs) in the forming LG, Krt14 was found in the whole embryonic LG epithelial basal cell layer. Interestingly, Krt19 specifically labeled the presumptive ductal domain and subsequently, the luminal cell layer. By combining these markers, the Fucci reporter mouse strain and genetic fate mapping of the Krt14+ population, we demonstrated that LG epithelium expansion is fuelled by a patterned cell proliferation, and to a lesser extent by epithelial reorganization and possible mesenchymal-to-epithelial transition. We pointed out that this epithelial reorganization, which is associated with apoptosis, regulated the lumen formation. Finally, we showed that the inhibition of Notch signaling prevented the ductal identity from setting, and led to a LG covered by ectopic TEBs. Taken together our results bring a deeper understanding on LG morphogenesis, epithelial domain identity, and organ expansion.

Early postnatal exposure to endosulfan interferes with the normal development of the male rat mammary gland

Our aim was to evaluate whether postnatal exposure to endosulfan (ENDO) modifies mammary gland (MG) development in pre- and post-pubertal male rats. From postnatal day 1 (PND1) to PND7, male rats were injected subcutaneously every 48h with either corn oil (vehicle) or 600μg ENDO/kg.bw. On PND21 and PND60, MG and blood samples were collected. Estradiol (E2) and testosterone (T) serum levels, MG histology, collagen fiber organization, proliferation index, and estrogen (ESR1) and androgen receptor (AR) expressions were evaluated. On PND21, E2 and T levels were similar between groups, whereas MG area, perimeter, number of terminal end buds and ESR1 expression were increased in ENDO-exposed rats. These changes were associated with alveolar development and increased organized collagen in the stroma. On PND60, a higher proliferation index in ENDO-exposed rats was correlated with a more developed lobuloalveolar structure. Hyperplastic alveoli and, hyperplastic ducts surrounded by a dense stroma were also observed in this group. T levels and ESR1 expression were similar between groups, whereas E2 levels and AR expression were decreased in ENDO-exposed rats. The exposure to ENDO in the first week of life interferes with the normal development of the MG and induces pre-malignant lesions in post-pubertal male rats.

A dioxin-like compound induces hyperplasia and branching morphogenesis in mouse mammary gland, through alterations in TGF-β1 and aryl hydrocarbon receptor signaling

Hexachlorobenzene (HCB) is a widespread environmental pollutant and a dioxin-like compound that binds weakly to the aryl hydrocarbon receptor (AhR). Because AhR and transforming growth factor β1 (TGF-β1) converge to regulate common signaling pathways, alterations in this crosstalk might contribute to developing preneoplastic lesions. The aim of this study was to evaluate HCB action on TGF-β1 and AhR signaling in mouse mammary gland, through AhR+/+ and AhR−/− models. Results showed a differential effect in mouse mammary epithelial cells (NMuMG), depending on the dose: 0.05μM HCB induced cell migration and TGF-β1 signaling, whereas 5μM HCB reduced cell migration, promoted cell cycle arrest and stimulated the dioxin response element (DRE) -dependent pathway. HCB (5μM) enhanced α-smooth muscle actin expression and decreased TGF-β receptor II mRNA levels in immortalized mouse mammary fibroblasts AhR+/+, resembling the phenotype of transformed cells. Accordingly, their conditioned medium was able to enhance NMuMG cell migration. Assays in C57/Bl6 mice showed HCB (3mg/kg body weight) to enhance ductal hyperplasia, cell proliferation, estrogen receptor α nuclear localization, branch density, and the number of terminal end buds in mammary gland from AhR+/+ mice. Primary culture of mammary epithelial cells from AhR+/+ mice showed reduced AhR mRNA levels after HCB exposure (0.05 and 5μM). Interestingly, AhR−/− mice exhibited an increase in ductal hyperplasia and mammary growth in the absence of HCB treatment, thus revealing the importance of AhR in mammary development. Our findings show that environmental HCB concentrations modulate AhR and TGF-β1 signaling, which could contribute to altered mammary branching morphogenesis, likely leading to preneoplastic lesions and retaining terminal end buds.

A new rapid and efficient method to estimate browse impacts from twig age

Abstract High densities of white-tailed deer restrict the regeneration of tree species, reduce understory cover and diversity, enhance invasions of exotic species, and facilitate the spread of human and deer diseases. Deer managers often base management decisions on estimated deer densities and carrying capacities, generating controversy. It may be simpler, cheaper, and more appropriate to manage deer populations in relation to their effects on local habitat conditions. Here, we describe a method based on the mean ages of woody twigs on saplings exposed to browsing. Growth can be traced back at least five years on deciduous species using terminal bud scale scars, generating estimates for the minimum interval between browsing events. We applied this method to three species of maple ( Acer ) growing in canopy gaps in- and outside a 5–7 year-old fenced deer exclosure in a mature forest in upper Michigan. Maples are palatable to deer but resprout readily after browsing. The method was simple and efficient to implement in the field with negligible among-observer variation. Mean twig age responded sensitively to differences in deer impacts among species, across the fence, and over time (all p Acer rubrum and pensylvanicum had lower mean twig ages than A. saccharum reflecting higher rates of browsing. Twig age showed a larger deer effect size and r 2 values than the sapling height or browse indicators (Cohen’s d = 34.85 vs. 1.39 and 9.55 for height and browse; r 2 = 0.556 vs. 0.154 and 0.331). Twig ages declined with height outside the fence while rising inside, providing a second independent indicator of deer impacts. Twig ages provide a direct indicator of deer browse on regenerating trees with lower sampling variance and higher independence from local environmental conditions than height or browse incidence. We should next test the twig age method in other contexts and species to confirm that it is an efficient, sensitive, and reliable indicator of deer impacts and habitat conditions.

DISPOSICIÓN DE PLANTAS DE TOMATE EN DOSELES EN FORMA DE ESCALERA BAJO DOS DENSIDADES DE POBLACIÓN

El manejo de la arquitectura de la planta es de suma importancia en sistemas de producción intensiva. El objetivo del presente estudio fue evaluar el crecimiento y rendimiento de plantas de tomate (Solanum lycopersicum L.) bajo un sistema de producción alternativo basado en el despunte temprano de las yemas terminales para dejar tres racimos por planta y alta densidad de población, en condiciones hidropónicas y bajo invernadero. Se compararon tres disposiciones de plantas con doseles en forma de escalera (escaleriformes) y una cuarta con dosel uniforme (testigo). Se usaron plantas de tomate Pik Ripe 461 de hábito de crecimiento determinado. Dentro de cada sistema de producción se probaron dos densidades de población (10 y 12.5 plantas m-2). Se utilizó un diseño de parcelas divididas en bloques al azar con cuatro repeticiones. En las parcelas grandes se evaluaron los sistemas de producción y en las subparcelas las densidades de población. Se analizaron características morfológicas y variables de rendimiento. Se encontró que las plantas con arreglos de dosel escaleriforme rindieron entre 18 y 21 % más por unidad de superficie que las de dosel uniforme, debido a que produjeron mayor cantidad de frutos sin una disminución significativa de su peso medio. La densidad de población con que se logró el mayor rendimiento (31 kg m-2) fue de 12.5 plantas m-2. El sistema de manejo propuesto fue efectivo para incrementar el rendimiento de tomate por unidad de superficie bajo condiciones de invernadero.

In vitro propagation of Actinidia melanandra Franch. and Actinidia rubricaulis Dunn. from shoot tip explants

ABSTRACTA highly efficient in vitro micropropagation protocol, using newly emerged sprouts coming from greenhouse-grown plants, was developed to produce Actinidia melanandra Franch. and Actinidia rubricaulis Dunn. This is the first report of in vitro culture of A. rubricaulis Dunn. Axenic culture was possible using one- or two-node explants or terminal buds, surface-sterilised with commercial bleach tablets. Nearly 90% success rate in establishment was observed. The best axillary shoot proliferation and maximum adventitious shoots elongation were achieved on Quoirin-Lepoivre medium supplemented with 1.5 mg L−1 6-benzyladenine and 30 g L−1 sucrose. Although used as an inert support, agar brand has a significant effect. Kobe agar at 8 g L−1 gave the best response. 100% of in vitro rooting was observed. Roots length and their quality were highly improved by the use of vermiculite in transfer medium. Over 99% of rooted plants survived after acclimatisation.

753 Dietary regulation of allometric ductal growth in the mammary glands

Development of the mammary glands is a continual process spanning from prenatal establishment of the epithelial primordium through to the full establishment of the secretory gland during lactation and its subsequent regression during involution. While the accretion of parenchymal tissue is greatest during phases such as gestation, it is the growth and establishment of the mammary ductal network prior to and during puberty that sets the stage for all subsequent periods of development and function. Depending on the species, ductal elongation can involve large amounts of epithelial proliferation and apoptosis in terminal end bud structures that interface with the surrounding stromal microenvironment. Ultimately all these processes are considered to be driven by a changing endocrine environment – but is it that simple? Of course, postnatal development also occurs against a changing nutritional background. Our findings from various models emphasize that dietary nutrients and plane of nutrition can dramatically impact mammary growth – either positively or negatively. We will review some of these key findings and summarize the potential for alternate mechanisms of ductal growth regulation in the mammary glands across species.

The expression of water channel proteins during human salivary gland development: a topographic study of aquaporins 1, 3 and 5

Some members of aquaporin family (AQP) plays crucial functions in salivary synthesis and secretion. These proteins expression has already been reported during salivary gland formation, however no previous studies in human developing glands have been performed. We evaluated AQP1, 3 and 5 expression through the stages of human salivary gland morphogenesis and discuss the possible role of AQP for glandular maturation. Human salivary glands derived from foetuses aged between 14 and 25 weeks were submitted to immunohistochemistry. At the bud stage, membrane expression of AQP1, 3 and 5 were observed within the epithelial bud cells presenting a similar apicolateral pattern, also found at the pseudoglandular stage, present within the terminal portions of future acini, while AQP5 was also particularly strong at the apical membrane of pre-acinar and pre-ductal cells. AQP5 was co-localised with Cytokeratin 7. Similar AQP1, 3 and 5 expression were observed at the following canalicular stage, where distinct and strongly luminal and acinar AQP5 expression is present. During the final terminal bud stage, AQP1 was only identified in serous acini, myoepithelial and endothelial cells, while differentiated mucous acinar cells and ducts were negative. AQP3 was detected at apicolateral membranes of both mucous and serous acini. AQP5 also showed a diffuse expression in mucous and serous acini, in addition to strong apical membrane expression within lumen of intercalated ductal cells. This topographic analysis of AQP1, 3 and 5 revealed differences in the expression pattern throughout salivary gland developmental stages, suggesting different roles for each protein in human glandular maturation.

Stearic acid suppresses mammary gland development by inhibiting PI3K/Akt signaling pathway through GPR120 in pubertal mice

It has been demonstrated that dietary high fat diet negatively affects the pubertal mammary gland development. The aim of the present study was to investigate the effects of stearic acid (SA), an 18-carbon chain saturated fatty acid, on mammary gland development in pubertal mice and to explore the underlying mechanism. Our results demonstrated that dietary supplementation of 2% SA suppressed mammary duct development, with significant reduction of terminal end bud (TEB) number and ductal branch. In accord, the expression of proliferative marker Cyclin D1 was markedly decreased by dietary SA. Furthermore, dietary SA led to increase of G protein-coupled receptor 120 (GPR120) expression and inhibition of PI3K/Akt signaling pathway in mammary gland of pubertal mice. In good agreement with the in vivo findings, the in vitro results showed that 40 μM SA significantly suppressed proliferation of mouse mammary epithelial cell HC11 by regulating mRNA and/or protein expression of proliferative markers such as Cyclin D1/3, p21, and PCNA. Meanwhile, SA activated GPR120 and inhibited PI3K/Akt signaling pathway in a GPR120-dependent manner. In addition, SA-induced inhibition of PI3K/Akt signaling pathway, suppression of HC11 proliferation, and alteration of proliferative markers expression were abolished by knockdown of GPR120 with siRNA. Collectively, these findings showed that SA suppressed mammary gland development of pubertal mice, which was coincident with the SA-inhibited HC11 proliferation, and was associated with inhibition of PI3K/Akt signaling pathway through activation of GPR120. These data provided new insights into the regulation of mammary gland development by dietary fatty acids.