Asymmetric leaves2 and elongator, a histone acetyltransferase complex, mediate the establishment of polarity in leaves of Arabidopsis thaliana

Leaf primordia are generated around the shoot apical meristem. Mutation of the ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana results in defects in repression of the meristematic and indeterminate state, establishment of adaxial-abaxial polarity and left-right symmetry in leaves. AS2 represses transcription of meristem-specific class 1 KNOX homeobox genes and of the abaxial-determinant genes ETTIN/ARF3, KANADI2 and YABBY5. To clarify the role of AS2 in the establishment of leaf polarity, we isolated mutations that enhanced the polarity defects associated with as2. We describe here the enhancer-of-asymmetric-leaves-two1 (east1) mutation, which caused the formation of filamentous leaves with abaxialized epidermis on the as2-1 background. Levels of transcripts of class 1 KNOX and abaxial-determinant genes were markedly higher in as2-1 east1-1 mutant plants than in the wild-type and corresponding single-mutant plants. EAST1 encodes the histone acetyltransferase ELONGATA3 (ELO3), a component of the Elongator complex. Genetic analysis, using mutations in genes involved in the biogenesis of a trans-acting small interfering RNA (ta-siRNA), revealed that ELO3 mediated establishment of leaf polarity independently of AS2 and the ta-siRNA-related pathway. Treatment with an inhibitor of histone deacetylases (HDACs) caused additive polarity defects in as2-1 east1-1 mutant plants, suggesting the operation of an ELO3 pathway, independent of the HDAC pathway, in the determination of polarity. We propose that multiple pathways play important roles in repression of the expression of class 1 KNOX and abaxial-determinant genes in the development of the adaxial domain of leaves and, thus, in the establishment of leaf polarity

Carbon-Ion Irradiation Suppresses Migration and Invasiveness of Human Pancreatic Carcinoma Cells MIAPaCa-2 via Rac1 and RhoA Degradation

PurposeTo investigate the mechanisms underlying the inhibition of cancer cell migration and invasion by carbon (C)-ion irradiation.Methods and MaterialsHuman pancreatic cancer cells MIAPaCa-2, AsPC-1, and BxPC-3 were treated by x-ray (4 Gy) or C-ion (0.5, 1, 2, or 4 Gy) irradiation, and their migration and invasion were assessed 2 days later. The levels of guanosine triphosphate (GTP)-bound Rac1 and RhoA were determined by the active GTPase pull-down assay with or without a proteasome inhibitor, and the binding of E3 ubiquitin ligase to GTP-bound Rac1 was examined by immunoprecipitation.ResultsCarbon-ion irradiation reduced the levels of GTP-bound Rac1 and RhoA, 2 major regulators of cell motility, in MIAPaCa-2 cells and GTP-bound Rac1 in AsPC-1 and BxPC-3 cells. Proteasome inhibition reversed the effect, indicating that C-ion irradiation induced Rac1 and RhoA degradation via the ubiquitin (Ub)-proteasome pathway. E3 Ub ligase X-linked inhibitor of apoptosis protein (XIAP), which directly targets Rac1, was selectively induced in C-ion–irradiated MIAPaCa-2 cells and coprecipitated with GTP-bound Rac1 in C-ion–irradiated cells, which was associated with Rac1 ubiquitination. Cell migration and invasion reduced by C-ion radiation were restored by short interfering RNA–mediated XIAP knockdown, indicating that XIAP is involved in C-ion–induced inhibition of cell motility.ConclusionIn contrast to x-ray irradiation, C-ion treatment inhibited the activity of Rac1 and RhoA in MIAPaCa-2 cells and Rac1 in AsPC-1 and BxPC-3 cells via Ub-mediated proteasomal degradation, thereby blocking the motility of these pancreatic cancer cells

Marked Hypertriglyceridemia in a Patient with type 2 Diabetes Receiving SGLT2 Inhibitors

A 43-year-old male with type 2 diabetes, under treatment with 5 mg/day of dapagliflozin, was referred to our hospital with upper left abdominal pain and marked hypertriglyceridemia (triglycerides [TGs], 5,960 mg/dl). He was also on a low-carbohydrate diet that promoted ketosis under sodium glucose cotransporter 2 (SGLT2) inhibitor administration. Polyacrylamide gel electrophoresis revealed a remarkable increase in very-low-den-sity lipoprotein, a TG-rich lipoprotein particle synthesized in the liver using free fatty acids derived from adi-pose tissue. Although SGLT2 inhibitors generally improve the lipid profile, under certain conditions such as a low-carbohydrate diet, they may adversely exacerbate the lipid profile via ketosis

ASYMMETRIC LEAVES2 and Elongator, a Histone Acetyltransferase Complex, Mediate the Establishment of Polarity in Leaves of Arabidopsis thaliana

Leaf primordia are generated around the shoot apical meristem. Mutation of the ASYMMETRIC LEAVES2 (AS2) gene of Arabidopsis thaliana results in defects in repression of the meristematic and indeterminate state, establishment of adaxial-abaxial polarity and left-right symmetry in leaves. AS2 represses transcription of meristem-specific class 1 KNOX homeobox genes and of the abaxial-determinant genes ETTIN/ARF3, KANADI2 and YABBY5. To clarify the role of AS2 in the establishment of leaf polarity, we isolated mutations that enhanced the polarity defects associated with as2. We describe here the enhancer-of-asymmetric-leaves-two1 (east1) mutation, which caused the formation of filamentous leaves with abaxialized epidermis on the as2-1 background. Levels of transcripts of class 1 KNOX and abaxial-determinant genes were markedly higher in as2-1 east1-1 mutant plants than in the wild-type and corresponding single-mutant plants. EAST1 encodes the histone acetyltransferase ELONGATA3 (ELO3), a component of the Elongator complex. Genetic analysis, using mutations in genes involved in the biogenesis of a trans-acting small interfering RNA (ta-siRNA), revealed that ELO3 mediated establishment of leaf polarity independently of AS2 and the ta-siRNA-related pathway. Treatment with an inhibitor of histone deacetylases (HDACs) caused additive polarity defects in as2-1 east1-1 mutant plants, suggesting the operation of an ELO3 pathway, independent of the HDAC pathway, in the determination of polarity. We propose that multiple pathways play important roles in repression of the expression of class 1 KNOX and abaxial-determinant genes in the development of the adaxial domain of leaves and, thus, in the establishment of leaf polarit

ATRIBUTOS POLARIMÉTRICOS DE IMAGEM RADAR NA INFERÊNCIA DE PARÂMETROS MORFOLÓGICOS DE MACRÓFITAS

O propósito deste trabalho é ajustar um modelo de regressão múltipla em função de atributos de imagens de radar polarimétrico, para estimativa da variável morfológica “volume da haste” de macrófitas encontradas na planície de inundação da Amazônia, no Lago Grande de Monte Alegre (Pará - Brasil). Com esta estimativa, pretende-se avaliar o potencial dos dados polarimétricos do sensor ALOS/PALSAR, destacando a importância da informação de fase das imagens de radar. Para este estudo, foram coletados dados de campo em época próxima à aquisição do dado de radar. Variáveis morfológicas, como altura e diâmetro da haste emergente, de três espécies de macrófitas foram medidas em campo e usadas para derivar o “volume da haste”, o qual foi modelado usando atributos da imagem de radar. Dois atributos da decomposição de Freeman-Durden, dois de Touzi e um de Pope apresentaram melhor desempenho na modelagem. Apesar do modelo não ter obtido um elevado coeficiente de determinação (44%), ele apresentou boa capacidade preditiva, já que todos os elementos de validação caíram dentro do intervalo de predição de 95% de confiança. Dentre as cinco variáveis independentes do modelo, quatro foram geradas a partir da informação de fase  das imagens, o que reforça a importância dessa informação.