Washington State University

About: Washington State University is a education organization based out in Pullman, Washington, United States. It is known for research contribution in the topics: Population & Gene. The organization has 26947 authors who have published 57736 publications receiving 2341509 citations. The organization is also known as: WSU & Wazzu.

Transcriptional regulators of stamen development in Arabidopsis identified by transcriptional profiling

Abstract: In Arabidopsis, jasmonate is required for stamen and pollen maturation. Mutants deficient in jasmonate synthesis, such as opr3, are male-sterile but become fertile when jasmonate is applied to developing flower buds. We have used ATH1 oligonucleotide arrays to follow gene expression in opr3 stamens for 22 h following jasmonate treatment. In these experiments, a total of 821 genes were specifically induced by jasmonate and 480 genes were repressed. Comparisons with data from previous studies indicate that these genes constitute a stamen-specific jasmonate transcriptome, with a large proportion (70%) of the genes expressed in the sporophytic tissue but not in the pollen. Bioinformatics tools allowed us to associate many of the induced genes with metabolic pathways that are probably upregulated during jasmonate-induced maturation. Our pathway analysis led to the identification of specific genes within larger families of homologues that apparently encode stamen-specific isozymes. Extensive additional analysis of our dataset identified 13 transcription factors that may be key regulators of the stamen maturation processes triggered by jasmonate. Two of these transcription factors, MYB21 and MYB24, are the only members of subgroup 19 of the R2R3 family of MYB proteins. A myb21 mutant obtained by reverse genetics exhibited shorter anther filaments, delayed anther dehiscence and greatly reduced male fertility. A myb24 mutant was phenotypically wild-type, but production of a myb21myb24 double mutant indicated that introduction of the myb24 mutation exacerbated all three aspects of the myb21 phenotype. Exogenous jasmonate could not restore fertility to myb21 or myb21myb24 mutant plants. Together with the data from transcriptional profiling, these results indicate that MYB21 and MYB24 are induced by jasmonate and mediate important aspects of the jasmonate response during stamen development.

Microwave-sintered 3D printed tricalcium phosphate scaffolds for bone tissue engineering.

Abstract: We report here the fabrication of three dimensional (3D) interconnected macro porous tricalcium phosphate (TCP) scaffolds with controlled internal architecture by direct 3D printing (3DP), and high mechanical strength by microwave sintering. TCP scaffolds with 27%, 35% and 41% designed macro porosity having pore sizes of 500 μm, 750 μm, and 1000 μm, respectively, have been fabricated via direct 3DP. These scaffolds are then sintered at 1150 °C and 1250 °C in conventional electric muffle furnace as well as microwave furnace. Total open porosity between 42% and 63% is obtained in the sintered scaffolds due to the presence of intrinsic micro pores along with the designed pores. A significant increase in compressive strength, between 46% and 69%, is achieved by microwave sintering as compared to conventional sintering as a result of efficient densification. A maximum compressive strength of 10.95 ± 1.28 MPa and 6.62 ± 0.67 MPa is achieved for scaffolds with 500 μm designed pores (~400 μm after sintering) sintered in microwave and conventional furnaces, respectively. An increase in cell density with a decrease in macro pore size is observed during in vitro cell-material interactions using human osteoblast cells. Histomorphological analysis reveals that the presence of both micro and macro pores facilitated osteoid like new bone formation when tested in the femoral defect on Sprague-Dawley rats. Our results show that bioresorbable 3D printed TCP scaffolds have great potential in tissue engineering applications for bone tissue repair and regeneration.

s - p Hybridization and Electron Shell Structures in Aluminum Clusters: A Photoelectron Spectroscopy Study

Abstract: Using photoelectron spectroscopy of size-selected ${\mathrm{Al}}_{x}^{\ensuremath{-}}$ $(x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1--162)$ clusters, we studied the electronic structure evolution of ${\mathrm{Al}}_{x}$ and observed that the Al $3s$- and $3p$-derived bands evolve and broaden with cluster size and begin to overlap at ${\mathrm{Al}}_{9}$. Direct spectroscopic signatures were obtained for electron shell structures with spherical shell closings at ${\mathrm{Al}}_{11}^{\ensuremath{-}}$, ${\mathrm{Al}}_{13}^{\ensuremath{-}}$, ${\mathrm{Al}}_{19}^{\ensuremath{-}}$, ${\mathrm{Al}}_{23}^{\ensuremath{-}}$, ${\mathrm{Al}}_{35}^{\ensuremath{-}}$, ${\mathrm{Al}}_{37}^{\ensuremath{-}}$, ${\mathrm{Al}}_{46}$, ${\mathrm{Al}}_{52}$, ${\mathrm{Al}}_{55}^{\ensuremath{-}}$, ${\mathrm{Al}}_{56}$, ${\mathrm{Al}}_{66}$, and ${\mathrm{Al}}_{73}^{\ensuremath{-}}$. The electron shell effect diminishes above ${\mathrm{Al}}_{75}$ and new spectral features appearing in ${\mathrm{Al}}_{x}^{\ensuremath{-}}$ $(xg100)$ suggest a possible geometrical packing effect in large clusters.