Broadening the impact of plant science through innovative, integrative, and inclusive outreach.

Population growth and climate change will impact food security and potentially exacerbate the environmental toll that agriculture has taken on our planet. These existential concerns demand that a passionate, interdisciplinary, and diverse community of plant science professionals is trained during the 21st century. Furthermore, societal trends that question the importance of science and expert knowledge highlight the need to better communicate the value of rigorous fundamental scientific exploration. Engaging students and the general public in the wonder of plants, and science in general, requires renewed efforts that take advantage of advances in technology and new models of funding and knowledge dissemination. In November 2018, funded by the National Science Foundation through the Arabidopsis Research and Training for the 21st century (ART 21) research coordination network, a symposium and workshop were held that included a diverse panel of students, scientists, educators, and administrators from across the US. The purpose of the workshop was to re-envision how outreach programs are funded, evaluated, acknowledged, and shared within the plant science community. One key objective was to generate a roadmap for future efforts. We hope that this document will serve as such, by providing a comprehensive resource for students and young faculty interested in developing effective outreach programs. We also anticipate that this document will guide the formation of community partnerships to scale up currently successful outreach programs, and lead to the design of future programs that effectively engage with a more diverse student body and citizenry.

Biaxial mechanical properties of the human thoracic and abdominal aorta, common carotid, subclavian, renal and common iliac arteries.

The biomechanics of large- and medium-sized arteries influence the pathophysiology of arterial disease and the response to therapeutic interventions. However, a comprehensive comparative analysis of human arterial biaxial mechanical properties has not yet been reported. Planar biaxial extension was used to establish the passive mechanical properties of human thoracic (TA, [Formula: see text]) and abdominal (AA, [Formula: see text]) aorta, common carotid (CCA, [Formula: see text]), subclavian (SA, [Formula: see text]), renal (RA, [Formula: see text]) and common iliac (CIA, [Formula: see text]) arteries from 11 deceased subjects ([Formula: see text] years old). Histological evaluation determined the structure of each specimen. Experimental data were used to determine constitutive parameters for a structurally motivated nonlinear anisotropic constitutive model. All arteries demonstrated appreciable anisotropy and large nonlinear deformations. Most CCA, SA, TA, AA and CIA specimens were stiffer longitudinally, while most RAs were stiffer circumferentially. A switch in anisotropy was occasionally demonstrated for all arteries. The CCA was the most compliant, least anisotropic and least frequently diseased of all arteries, while the CIA and AA were the stiffest and the most diseased. The severity of atherosclerosis correlated with age, but was not affected by laterality. Elastin fibers in the aorta, SA and CCA were uniformly and mostly circumferentially distributed throughout the media, while in the RA and CIA, elastin was primarily axially aligned and concentrated in the external elastic lamina. Constitutive modeling provided good fits to the experimental data for most arteries. Biomechanical and architectural features of major arteries differ depending on location and functional environment. A better understanding of localized arterial mechanical properties may support the development of site-specific treatment modalities for arterial disease.

Adaptation of an ecdysone-based genetic switch for transgene expression in soybean seeds.

Soybean was used as a model for studies of chemical induction of gene expression in seeds. A chimeric transcriptional activator, VGE, driven by the soybean seed glycinin G1 promoter, was used to induce the expression of an ER-targeted GFP(KDEL) reporter protein upon addition of the chemical ligand, methoxyfenozide. The chemical gene switch activated gene expression under in vitro conditions in somatic cotyledonary embryos and zygotic seed embryos cultured from transgenic soybean plants, as well as in seeds in planta under greenhouse conditions. The efficiency of induction of GFP expression under different growth conditions was strongly influenced by the developmental stage of the seed and availability of the inducer. The formation of ER-derived GFP-containing protein bodies in seed storage parenchyma cells was correlated with the level of induced expression.

Production of Escherichia coli heat labile toxin (LT) B subunit in soybean seed and analysis of its immunogenicity as an oral vaccine.

The B subunit of the heat labile toxin of enterotoxigenic Escherichia coli (LTB) was used as a model immunogen for production in soybean seed. LTB expression was directed to the endoplasmic reticulum (ER) of seed storage parenchyma cells for sequestration in de novo synthesized inert protein accretions derived from the ER. Pentameric LTB accumulated to 2.4% of the total seed protein at maturity and was stable in desiccated seed. LTB-soybean extracts administered orally to mice induced both systemic IgG and IgA, and mucosal IgA antibody responses, and was particularly efficacious when used in a parenteral prime-oral gavage boost immunization strategy. Sera from immunized mice blocked ligand binding in vitro and immunized mice exhibited partial protection against LT challenge. Moreover, soybean-expressed LTB stimulated the antibody response against a co-administered antigen by 500-fold. These results demonstrate the utility of soybean as an efficient production platform for vaccines that can be used for oral delivery.

Ecdysone agonist-inducible expression of a coat protein gene from tobacco mosaic virus confers viral resistance in transgenic Arabidopsis.

Constitutive expression of a gene encoding tobacco mosaic virus (TMV) coat protein (CP) in transgenic plants confers resistance to infection by TMV and related tobamoviruses. Here, we examined resistance to TMV by temporal and quantitative control of TMV Cg CP (CgCP) gene expression using a simple, methoxyfenozide-inducible system in Arabidopsis plants. By soil drenching with a commercial ecdysone agonist (Intrepid-2F/methoxyfenozide), most transgenic lines were induced from undetectable levels of gene expression to protein levels from 0.05 to 0.8% (w/w) of CgCP. This corresponds to up to four times the amount of CP produced by the constitutive cauliflower mosaic virus (CaMV) double 35S promoter. CgCP transcripts were induced by 700-fold, without changing the expression patterns of pathogenesis-related (PR) genes. The high level of accumulation of CgCP was sufficient to produce large amounts of virus-like particles that accumulate in large aggregates throughout the cells. In virus challenge assays, treatment with Intrepid-2F prior to TMV infection resulted in high levels of viral resistance, while no treatment or treatment with the inducer following infection did not confer resistance. This report demonstrates chemically controlled disease resistance and confirms the utility of the ecdysone agonist-inducible system under greenhouse conditions.

Targeting of CD45 protein tyrosine phosphatase activity to lipid microdomains on the T cell surface inhibits TCR signaling.

CD45, a transmembrane protein tyrosine phosphatase (PTP), can either positively or negatively regulate Src-family protein tyrosine kinase (PTK) activity in vivo. It is proposed that TCR-initiated signaling requires the segregation of PTP activities from the engaged TCR, based upon the differential membrane compartmentalization on the T cell surface. To test the importance of CD45 exclusion from lipid microdomains for proper TCR signaling, a chimeric molecule was generated by fusing the CD45 cytoplasmic region, which contains the PTP domains, to the amino-terminal 12 amino acids of Lck, which target Lck to lipid microdomains. Using 3A9 T lymphocyte hybridoma (3A9H) cells whose TCR recognizes hen egg-white lysozyme (HEL), Lck-CD45 expression resulted in its targeting to lipid microdomains. The 3A9H cells expressing Lck-CD45 were reduced in their responses to HEL or co-cross-linking of CD3 and CD4, as assessed by IL-2 production and Ca(2+) mobilization. Src-family PTK activity associated with lipid microdomains was also decreased. These results suggest that the segregation of CD45 from proximal TCR signaling components is necessary for TCR signaling and that the targeting of CD45 PTP activity to lipid microdomains on the T cell surface results in decreased sensitivity of TCR-mediated signaling.

Absence of apparent phenotype in mice lacking Cdc25C protein phosphatase.

The Cdc25 family of protein phosphatases positively regulate the cell division cycle by activating cyclin-dependent protein kinases. In humans and rodents, three Cdc25 family members denoted Cdc25A, -B, and -C have been identified. The murine forms of Cdc25 exhibit distinct patterns of expression both during development and in adult mouse tissues. In order to determine unique contributions made by the Cdc25C protein phosphatase to embryonic and adult cell cycles, mice lacking Cdc25C were generated. We report that Cdc25C(-/-) mice are viable and do not display any obvious abnormalities. Among adult tissues in which Cdc25C is detected, its transcripts are most abundant in testis, followed by thymus, ovary, spleen, and intestine. Mice lacking Cdc25C were fertile, indicating that Cdc25C does not contribute an essential function during spermatogenesis or oogenesis in the mouse. T- and B-cell development was also found to be normal in Cdc25C(-/-) mice, and Cdc25C(-/-) mouse splenic T and B cells exhibited normal proliferative responses in vitro. Finally, the phosphorylation status of Cdc2, the timing of entry into mitosis, and the cellular response to DNA damage were unperturbed in mouse embryo fibroblasts lacking Cdc25C. These findings indicate that Cdc25A and/or Cdc25B may compensate for loss of Cdc25C in the mouse.

The sialoadhesin CD33 is a myeloid-specific inhibitory receptor.

Activating and inhibitory receptors act in concert to regulate cellular activation. Inhibitory receptors are characterized by the presence of a characteristic sequence known as an immunoreceptor tyrosine-based inhibitory motif (ITIM) in their cytoplasmic tail. Phosphorylated ITIM serve as docking sites for the SH2-containing phosphatases which then inhibit signal transduction. CD33 is a member of the immunoglobulin superfamily and contains two immunoglobulin-like domains, a transmembrane region and a cytoplasmic tail that has two potential ITIM sequences. CD33 expression is restricted to cells of myelomonocytic lineage. The precise function of CD33 is unknown although it is a lectin that binds sialic acid residues in N- and O-glycans on cell surfaces. Co-immunoprecipitation studies demonstrate that CD33 associates with the SH2-containing tyrosine phosphatase SHP-1 in monocytes. The proximal ITIM is necessary and sufficient for SHP-1 binding which is mediated by the aminoterminal SH2 domain. Treatment of SHP-1 with a phosphopeptide representing the proximal CD33 ITIM results in increased SHP-1 enzymatic activity. CD33 exerts an inhibitory effect on tyrosine phosphorylation and Ca(2+) mobilization when co-engaged with the activating FcgammaRI receptor. This data indicates that CD33 is an inhibitory receptor that may regulate FcgammaRI signal transduction.

Cloning and characterization of a cdc25 phosphatase from mouse lymphocytes.

Members of the cdc25 phosphatase family are proposed to function as important regulators of the eukaryotic cell cycle, particularly in the induction of mitotic events. A new cdc25 tyrosine phosphatase, cdc25M1, has been cloned from a mouse pre-B cell cDNA library and characterized. The cdc25M1 protein consists of 465 amino acids with a predicted relative molecular mass (M(r)) of 51,750. Over the highly conserved carboxyl terminal region, the amino acid sequence similarity to the human cdc25 C or Hs1 isoform is 89%, while the overall similarity is 67%. The phosphatase active site is located within residues 367-374. Tissue expression of the cdc25M1 was highest in mouse spleen and thymus by northern blot analysis. The cdc25M1 mRNA was detected in a number of cloned mouse lymphocyte cell lines including both CD8+ and CD4+ cells. cdc25M1 mRNA was shown to be cell cycle-regulated in T cells following interleukin-2 (IL-2)-stimulation. Accumulation of cdc25M1 mRNA occurred at 48 h after IL-2 stimulation, when lymphocytes were progressing from S phase to G2/M phase of the cell cycle. This pattern of expression is in contrast to that observed for other protein tyrosine phosphatases expressed in T lymphocytes including CD45, LRP, SHP, and PEP. The elevation in cdc25M1 mRNA level occurred concomittant to the appearance of the hyperphosphorylated form of p34cdc2 protein kinase. A purified, bacterial-expressed recombinant cdc25M1 phosphatase domain catalyzed the dephosphorylation of p-nitrophenol phosphate, as well as [32P-Tyr] and [32P-Ser/Thr]-containing substrates. Preincubation of p34cdc2 kinase with cdc25M1 activated its histone H1 kinase activity in vitro. These results suggest that cdc25M1 may be involved in regulating the proliferation of mouse T lymphocytes following cytokine stimulation, through its action on p34cdc2 kinase.

The leukocyte common antigen, CD45 and other protein tyrosine phosphatases in hematopoietic cells.

Numerous protein tyrosine phosphatases have been characterized that are expressed by hematopoietic-derived cells. CD45, a transmembrane protein tyrosine phosphatase expressed by all nucleated cells of hematopoietic origin, has been a prototype for studying the function of these enzymes. In T lymphocytes, CD45 serves to dephosphorylate and activate members of the Src-tyrosine kinase family. Without CD45 function, T cells cannot respond to antigen. Therefore, CD45 functions positively to regulate lymphocyte activation. The characteristics of other protein tyrosine phosphatases found in hematopoietic-derived cells suggests that they are also essential in regulating cell differentiation and activation.

Expression of a protein tyrosine phosphatase in normal and v-src-transformed mouse 3T3 fibroblasts.

A rat cDNA encoding a 51-kD protein tyrosine phosphatase (PTP1) was cloned into a mammalian expression vector and transfected into normal and v-src-transformed mouse NIH 3T3 fibroblasts. In the stable subclones isolated, PTP1 expression at the mRNA level was elevated twofold to 25-fold. The highest constitutive level of phosphotyrosine-specific dephosphorylating activity observed without cytotoxic effects or significant clonal instability was approximately 10-fold over the endogenous activity. The expressed PTP1 was found to be associated with the particulate fraction of the fibroblasts. Subcellular fractionation and immunofluorescent microscopic examination of PTP1-overexpressing cells has shown the phosphatase to be localized to the reticular network of the ER. PTP1 was readily solubilized by detergents, but not by high salt. Limited proteolysis of membrane-associated PTP1 resulted in the release of lower molecular mass (48 and 37 kD) forms of the enzyme to the cytosol. Thermal phase partitioning of isolated membranes with Triton X-114 indicated that the full-length PTP1 was strongly integrated into the membrane in contrast to the proteolytically derived fragments of PTP1. Overexpression of PTP1 caused little apparent change in the rate of cell proliferation, but did induce changes in fibroblast morphology. A substantial increase in the proportion of bi- and multinucleate cells in PTP1-expressing cell populations was observed, and, in the case of the v-src-transformed cells, cell flattening and loss of refractibility occurred. Although no apparent difference in the tyrosine phosphorylation of pp60v-src was noted in v-src-transformed control and PTP1-overexpressing fibroblasts, the phosphotyrosine content of a 70-kD polypeptide was decreased in PTP1-overexpressing cells.