RESUMO

Plants synchronize their growth and development with environmental changes, which is critical for their survival. Among their life cycle transitions, seed germination is key for ensuring the survival and optimal growth of the next generation. However, even under favorable conditions, oftentimes germination can be blocked by seed dormancy, a regulatory multilayered checkpoint integrating internal and external signals. Intricate genetic and epigenetic mechanisms underlie seed dormancy establishment, maintenance, and release. In this review, we focus on recent advances that shed light on the complex mechanisms associated with physiological dormancy, prevalent in seed plants, with Arabidopsis thaliana serving as a model. Here, we summarize the role of multiple epigenetic regulators, but with a focus on histone modifications like acetylation and methylation, that finely tune dormancy responses and influence dormancy-associated gene expression. Understanding these mechanisms can lead to a better understanding of seed biology in general, as well as result in the identification of possible targets for breeding climate-resilient plants.

RESUMO

Abstract In view of the morphological similarity between gastrointestinal stromal tumors (GIST) and other sarcomas of the intestine of dogs, the aim was to carry out the histomorphological and immunohistochemical diagnosis of these tumors, associating breed, sex and age, location and tumor invasion. 217 cases were evaluated by histopathology and 36 diagnosed by immunohistochemistry were included (24 GIST and 12 other intestinal sarcomas). Mixed breed dogs were the most diagnosed with GIST, mainly elderly females (9.5±2.2 years); in the other intestinal sarcomas, crossbreeds and Dachshunds, males and females, were equally affected. The cecum was the most affected by GISTs, with tumor invasion of the intestinal layers in all cases. The small intestine was the most affected by the other intestinal sarcomas, with invasion of the layers in most of these tumors. GISTs expressed markers such as CD117 and DOG-1, unlike other intestinal sarcomas. GIST and other intestinal sarcomas denoted histomorphological and immunophenotypic characteristics similar to histopathology, justifying the association of immunohistochemistry for the definitive diagnosis.

Resumo Tendo em vista a semelhança morfológica entre tumores estromais gastrointestinais (GIST) e outros sarcomas do intestino de cães, objetivou-se realizar o diagnóstico histomorfológico e imunoistoquímico desses tumores, associando raça, sexo e idade, localização e invasão tumoral. Foram avaliados 217 casos por histopatologia e incluídos 36 diagnosticados por imuno-histoquímica (24 GIST e 12 outros sarcomas intestinais). Cães sem raça definida foram os mais diagnosticados com GIST, principalmente fêmeas idosas (9,5±2,2 anos); nos demais sarcomas intestinais, mestiços e Dachshunds, machos e fêmeas, foram igualmente acometidos. O ceco foi o mais acometido pelos GISTs, com invasão tumoral das camadas intestinais em todos os casos. O intestino delgado foi o mais acometido pelos demais sarcomas intestinais, com invasão das camadas na maioria desses tumores. GISTs expressaram marcadores como CD117 e DOG-1, ao contrário de outros sarcomas intestinais. O GIST e outros sarcomas intestinais denotaram características histomorfológicas e imunofenotípicas semelhantes à histopatologia, justificando a associação da imuno-histoquímica para o diagnóstico definitivo.

RESUMO

The relief of dormancy and the promotion of seed germination are of extreme importance for a successful seedling establishment. Although alternating temperatures and light are signals promoting the relief of seed dormancy, the underlying mechanisms of their interaction in seeds are scarcely known. By exposing imbibed Arabidopsis thaliana dormant seeds to two-day temperature cycles previous of a red light pulse, we demonstrate that the germination mediated by phytochrome B requires the presence of functional PSEUDO-RESPONSE REGULATOR 7 (PRR7) and TIMING OF CAB EXPRESSION 1 (TOC1) alleles. In addition, daily cycles of alternating temperatures in darkness reduce the protein levels of DELAY OF GERMINATION 1 (DOG1), allowing the expression of TOC1 to induce seed germination. Our results suggest a functional role for some components of the circadian clock related with the action of DOG1 for the integration of alternating temperatures and light signals in the relief of seed dormancy. The synchronization of germination by the synergic action of light and temperature through the activity of circadian clock might have ecological and adaptive consequences.

Assuntos

RESUMO

Gastrointestinal stromal tumor (GIST) accounts for nearly 1% of all gastrointestinal tumors. Its association with renal transplantation is not frequent. Approximately 95% of GIST show staining for CD177. DOG1 is a recently described monoclonal antibody that shows positivity even in the absence of CD177 staining. The diagnosis of GIST should be pursued because of the availability of very effective treatments with tyrosine-kinase inhibitors. Herein, we describe the case of a woman with renal transplant who presented a small bowel GIST and weak positivity for CD177, treated initially with surgery. Tumor recurrence was documented 3 years later and histopatology showed loss of CD177 staining and positivity for DOG1. She was treated with imatimib without further recurrence after five years of follow up.

Assuntos

RESUMO

El tumor estromal gastrointestinal (GIST) representa alrededor del 1% de todos los tumores digestivos y su aparición en pacientes trasplantados renales es infrecuente. Aproximadamente el 95% muestra tinción positiva para c-kit/CD117. DOG1 es un anticuerpo recientemente descrito que se sobre-expresa en los GIST, incluso en c-kit/ CD117 negativos. El diagnóstico preciso de GIST resulta imperativo, debido a la disponibilidad y la creciente eficacia de los inhibidores de la tirosina quinasa en estos tumores, incluso en el subgrupo c-kit/ CD117 negativo. Se presenta el caso de una mujer trasplantada renal inicialmente con GIST en intestino delgado y débil positividad para CD117 tratada con cirugía y recidiva tumoral a los tres años, pérdida de la expresión CD117 y tinción positiva para DOG1. Recibió tratamiento exitoso con imatimib sin presentar recaída tumoral durante un seguimiento de cinco años.

Gastrointestinal stromal tumor (GIST) accounts for nearly 1% of all gastrointestinal tumors. Its association with renal transplantation is not frequent. Approximately 95% of GIST show staining for CD177. DOG1 is a recently described monoclonal antibody that shows positivity even in the absence of CD177 staining. The diagnosis of GIST should be pursued because of the availability of very effective treatments with tyrosine-kinase inhibitors. Herein, we describe the case of a woman with renal transplant who presented a small bowel GIST and weak positivity for CD177, treated initially with surgery. Tumor recurrence was documented 3 years later and histopatology showed loss of CD177 staining and positivity for DOG1. She was treated with imatimib without further recurrence after five years of follow up.

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RESUMO

BACKGROUND: Polymorphous low-grade adenocarcinoma (PLGA) remains a diagnostic challenge for most pathologists due to its large spectrum of histological patterns. In this study, the expression of two new markers recently described for salivary gland tumors was studied in PLGA. METHODS: The morphology of 33 cases of PLGA was carefully evaluated using hematoxylin-and-eosin-stained sections and confirmed by immunohistochemistry for cytokeratin 7, vimentin, and S-100. Periodic acid-Schiff with diastase digestion was also used. The expression of mammaglobin and DOG-1 was carried out using the EnVision System. Mammaglobin was assessed according to the percentage of positively stained tumor cells, while DOG-1 was evaluated according to its presence and site. For MCM-2 and Ki-67, markers of proliferation, the labeling index of cell nuclei positivity was evaluated using total cell number. The ETV6-NTRK3 fusion was examined by fluorescence in situ hybridization analysis. RESULTS: The histological patterns of the tumor were classified as lobular or non-lobular. For the non-lobular pattern, tubular, cribriform, glomeruliform, trabecular, and papillary patterns were observed. Mammaglobin was present in all PLGA cases, and its expression was stronger (P = 0.01) in the lobular than in the non-lobular pattern. The expression of DOG-1 was present in the apical portion and cytoplasm of the cells. Proliferation markers were low for all cases independent of histological pattern. CONCLUSIONS: Polymorphous low-grade adenocarcinoma has been confirmed to originate from the intercalated duct and to feature high expression of mammaglobin in its lobular pattern resembling that of mammary secretory analogue carcinoma, except for the ETV6 gene rearrangement.

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Lysozyme is an enzymatic marker of acinar and intercalated duct cells of normal salivary glands. The aim of this study was to verify whether lysozyme expression could be useful to distinguish acinic cell carcinoma (ACC) from its main mimic, mammary analog secretory carcinoma (MASC). For comparison, DOG1 expression was analyzed as well. Seventeen cases of ACC, 15 MASC, and 125 other salivary tumors were studied. Lysozyme expression was found in tumor cells as well as in secreted material of MASC (86.6 % of cases) and in ductal cells of epithelial-myoepithelial carcinoma (EMC-53.8 %), pleomorphic adenoma (PA-29.1 %) and polymorphous low-grade adenocarcinoma (PLGA-23.8 %). However, in ACC, lysozyme was not expressed. Three patterns of DOG1 staining were seen: apical-luminal, cytoplasmic, and mixed cytoplasmic/membranous. The apical-luminal pattern was detected in ductal cells of ACC (58.8 % of cases), EMC (38.4 %), adenoid-cystic carcinoma (AdCC-35.3 %), PA (8.3 %), and PLGA (4.8 %). These tumors also showed mixed membranous/cytoplasmic staining for DOG1. MASC, mucoepidermoid, and salivary duct carcinomas exhibited only DOG1 cytoplasmic staining. In conclusion, lysozyme cannot be used as a marker of acinar differentiation in salivary tumors. However, lysozyme expression can be helpful to distinguish MASC from ACC due to its high frequency in the former and absence in ACC. It is likely that in MASC, lysozyme expression may reflect a lactational-like secretory differentiation since lysozyme belongs to breast milk proteins. Regarding DOG1 expression, the apical-luminal pattern is related to acinar and intercalated duct differentiation whereas the cytoplasmic staining does not seem to be associated with a specific cellular phenotype.

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