Browsing by Author "Wolff, David W."
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- Evaluation of anther-derived, inbred, and hybrid populations of Streptocarpus X hybridus VossWolff, David W. (Virginia Tech, 1985-08-05)The potential of inbreeding and selective hybridization, along with anther culture, for increasing homogeneity with 2 early flowering cultivars of Streptocarpus X hybridus was examined. A 'Concorde' and 'Mixed Nymph' genotype expressed inbreeding depression within 2 generations, characterized by a reduction in corolla, leaf, and peduncle size, as well as an increase in floral deformities (flower part fusions). Inbred populations contained individuals which resembled the parent cultivars for several morphological traits. Such could be selected by cluster analysis of important traits, for the development of inbreeding depression resistant lines for hybrid production of more uniform, seed-propagated Streptocorpus cultivars. Reciprocal differences were observed among hybrids of first-generation inbreds, suggesting that female parent selection is critical for certain ornamental traits such as corolla size and peduncle length. Plants were regenerated from anther-derived callus of ‘Concorde’ and 'Mixed Nymph'. The plants were found to be of somatic cell origin, but exhibited somaclonal variation for overall morphology. Variation for leaf variegation and morphology, days to flowering, flowers per peduncle, peduncle length and leaf area were observed among progeny of anther-derived plants, indicating that heritable somaclonal variation in Streptocarpus may be exploited for increased genetic diversity for cultivar development.
- Phosphorylation of guanosine monophosphate reductase triggers a GTP-dependent switch from pro- to anti-oncogenic function of EPHA4Wolff, David W.; Deng, Zhiyong; Bianchi-Smiraglia, Anna; Foley, Colleen E.; Han, Zhannan; Wang, Xingyou; Shen, Shichen; Rosenberg, Masha M.; Moparthy, Sudha; Yun, Dong Hyun; Chen, Jialin; Baker, Brian K.; Roll, Matthew; Magiera, Andrew J.; Li, Jun; Hurley, Edward; Feltri, Maria Laura; Cox, Anderson O.; Lee, Jingyun; Furdui, Cristina M.; Liu, Liang; Bshara, Wiam; LaConte, Leslie E. W.; Kandel, Eugene S.; Pasquale, Elena B.; Qu, Jun; Hedstrom, Lizbeth; Nikiforov, Mikhail A. (Cell Press, 2022-02-10)Signal transduction pathways post-translationally regulating nucleotide metabolism remain largely unknown. Guanosine monophosphate reductase (GMPR) is a nucleotide metabolism enzyme that decreases GTP pools by converting GMP to IMP. We observed that phosphorylation of GMPR at Tyr267 is critical for its activity and found that this phosphorylation by ephrin receptor tyrosine kinase EPHA4 decreases GTP pools in cell protrusions and levels of GTP-bound RAC1. EPHs possess oncogenic and tumor-suppressor activities, although the mechanisms underlying switches between these two modes are poorly understood. We demonstrated that GMPR plays a key role in EPHA4-mediated RAC1 suppression. This supersedes GMPR-independent activation of RAC1 by EPHA4, resulting in a negative overall effect on melanoma cell invasion and tumorigenicity. Accordingly, EPHA4 levels increase during melanoma progression and inversely correlate with GMPR levels in individual melanoma tumors. Therefore, phosphorylation of GMPR at Tyr267 is a metabolic signal transduction switch controlling GTP biosynthesis and transformed phenotypes.