The malignant phenotype in breast cancer is driven by aberrant signal transduction pathways. Mixed-lineage kinase-3 (MLK3) is a mammalian mitogen-activated protein kinase kinase kinase (MAP3K) that activates multiple MAPK pathways. Depending on the cellular context, MLK3 has been implicated in apoptosis, proliferation, migration and differentiation. Here we investigated the effect of MLK3 and its signaling to MAPKs in the acquisition of malignancy in breast cancer. We show that MLK3 is highly expressed in breast cancer cells. We provide evidence that MLK3's catalytic activity and signaling to c-jun N-terminal kinase (JNK) is required for migration of highly invasive breast cancer cells and for MLK3-induced migration of mammary epithelial cells. Expression of active MLK3 is sufficient to induce the invasion of mammary epithelial cells, which requires AP-1 activity and is accompanied by the expression of several proteins corresponding to AP-1-regulated invasion genes. To assess MLK3's contribution to the breast cancer malignant phenotype in a more physiological setting, we implemented a strategy to inducibly express active MLK3 in the preformed acini of MCF10A cells grown in 3D Matrigel. Induction of MLK3 expression dramatically increases acinar size and modestly perturbs apicobasal polarity. Remarkably, MLK3 expression induces luminal repopulation and suppresses the expression of the pro-apoptotic protein BimEL, as has been observed in Her2/Neu-expressing acini. Taken together, our data show that MLK3-JNK-AP-1 signaling is critical for breast cancer cell migration and invasion. Our current study uncovers both a proliferative and novel antiapoptotic role for MLK3 in the acquisition of a malignant phenotype in mammary epithelial cells. Thus, MLK3 may be an important therapeutic target for the treatment of invasive breast cancer.

The involvement of Rhizobium enzymes that degrade plant cell wall polymers has long been an unresolved question about the infection process in root nodule symbiosis. Here we report the production of enzymes from Rhizobium leguminosarum bv. trifolii that degrade carboxymethyl cellulose and polypectate model substrates with sensitive methods that reliably detect the enzyme activities: a double-layer plate assay, quantitation of reducing sugars with a bicinchoninate reagent, and activity gel electrophoresis-isoelectric focusing. Both enzyme activities were (i) produced commonly by diverse wild-type strains, (ii) cell bound with at least some of the activity associated with the cell envelope, and (iii) not changed appreciably by growth in the presence of the model substrates or a flavone that activates expression of nodulation (nod) genes on the resident symbiotic plasmid (pSym). Equivalent levels of carboxymethyl cellulase activity were found in wild-type strain ANU843 and its pSym-cured derivative, ANU845, consistent with previous results of Morales et al. (V. Morales, E. Martínez-Molina, and D. Hubbell, Plant Soil 80:407-415, 1984). However, polygalacturonase activity was lower in ANU845 and was not restored to wild-type levels in the recombinant derivative of pSym- ANU845 containing the common and host-specific nod genes within a 14-kb HindIII DNA fragment of pSym from ANU843 cloned on plasmid pRt032. Activity gel electrophoresis resolved three carboxymethyl cellulase isozymes of approximately 102, 56, and 33 kDa in cell extracts from ANU843. Isoelectric focusing activity gels revealed one ANU843 polygalacturonase isozyme with a pI of approximately 7.2. These studies show that R. leguminosarum bv. trifolii produces multiple enzymes that cleave glycosidic bonds in plant cell walls and that are cell bound.

Coordinated, Open, Networked (ICON) principles in the American Geophysical Union Biogeosciences section, and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: (a) Global collaboration, technology transfer, and application (Section 2), (b) Community engagement, community science, education, and stakeholder involvement (Section 3), and (c) Field, experimental, remote sensing, and real-time data research and application (Section 4). We discuss needs and strategies for implementing ICON and outline short-and long-term goals. The inclusion of global data and international community engagement are key to tackling grand challenges in biogeosciences. Although recent technological advances and growing open-access information across the world have enabled global collaborations to some extent, several barriers, ranging from technical to organizational to cultural, have remained in advancing interoperability and tangible scientific progress in biogeosciences. Overcoming these hurdles is necessary to address pressing large-scale research questions and applications in the biogeosciences, where ICON principles are essential. Here, we list several opportunities for ICON, including coordinated experimentation and field observations across global sites, that are ripe for implementation in biogeosciences as a means to scientific advancements and social progress. Plain Language SummaryBiogeosciences is an interdisciplinary field that requires multiscale global data and concerted international community efforts to tackle grand challenges. However, several technical, institutional, and cultural hurdles have remained as major roadblocks toward scientific progress, hindering seamless global data acquisition and international community engagement. To bring a paradigm shift in biogeosciences, there is a need to implement integrated, coordinated, open, and networked efforts, collectively known as the Integrated, Coordinated, Open, Networked (ICON) principles. In this article, we present three related commentaries about the state of ICON, discuss needs to reduce geographical bias in data for enhancing scientific progress, and identify action items. Action items are primarily people-centric DWIVEDI ET AL.

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