Browsing by Author "Becker, Jorg D."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Absence of functional TolC protein causes increased stress response gene expression in Sinorhizobium melilotiPublication . Santos, Mario R.; Cosme, Ana M.; Becker, Jorg D.; Medeiros, Joao M C.; Mata, Marcia F.; Moreira, Leonilde M.The TolC protein from Sinorhizobium meliloti has previously been demonstrated to be required for establishing successful biological nitrogen fixation symbiosis with Medicago sativa. It is also needed in protein and exopolysaccharide secretion and for protection against osmotic and oxidative stresses. Here, the transcriptional profile of free-living S. meliloti 1021 tolC mutant is described as a step toward understanding its role in the physiology of the cell.
- BOLITA, an Arabidopsis AP2/ERF-like transcription factor that affects cell expansion and proliferation/differentiation pathwaysPublication . Marsch-Martinez, Nayelli; Greco, Raffaella; Becker, Jorg D.; Dixit, Shital; Bergervoet, Jan H. W.; Karaba, Aarati Aarati; de Folter, Stefan; Pereira, AndyThe BOLITA (BOL) gene, an AP2/ERF transcription factor, was characterized with the help of an activation tag mutant and overexpression lines in Arabidopsis and tobacco. The leaf size of plants overexpressing BOL was smaller than wild type plants due to a reduction in both cell size and cell number. Moreover, severe overexpressors showed ectopic callus formation in roots. Accordingly, global gene expression analysis using the overexpression mutant reflected the alterations in cell proliferation, differentiation and growth through expression changes in RBR, CYCD, and TCP genes, as well as genes involved in cell expansion (i.e. expansins and the actin remodeling factor ADF5). Furthermore, the expression of hormone signaling (i.e. auxin and cytokinin), biosynthesis (i.e. ethylene and jasmonic acid) and regulatory genes was found to be perturbed in bol-D mutant leaves
- How many genes are needed to make a pollen tube? lessons from transcriptomicsPublication . Becker, Jorg D.; Feijó, José ABackground Pollen is the male gametophyte of higher plants. Upon pollination, it germinates and develops into a fast-growing cytoplasmic extension, the pollen tube, which ultimately delivers the sperm into the ovary. The biological relevance of its role, and the uniqueness of this kind of cellular organization, have made pollen the focus of many approaches, and it stands today as one of the best-known models in plant cell biology. In contrast, the genetic background of its development has been until recently largely unknown. Some genes involved have been described and a few functional mutants have been characterized, but only to a limited extent and allowing only a limited understanding of the regulatory mechanisms. Yet, being a relatively simple organ (2 or 3 cells), pollen stands as an excellent target for molecular-biology-based approaches. Recent studies on Arabidopsis thaliana have characterized the transcriptional profile of pollen grains and microgametogenesis in comparison to sporophytic tissues. They underline the unique characteristics of pollen, not only in terms of a strongly reduced set of genes being expressed, but also in terms of the functions of the proteins encoded and the pathways they are involved in. These approaches have expanded the number of genes with known expression in pollen from a few hundred to nearly eight thousand. While for the first time allowing systems and/or gene-family approaches, this information also expands dramatically the possibility of hypothesis-driven experimentation based on specific gene function predictions. Recent studies reveal this to be the case in, for example, transcriptional regulation, cell-cycle progression and gene-silencing mechanisms in mature pollen
- Identification and functional analysis of novel genes expressed in the Anterior Visceral EndodermPublication . Goncalves, Lisa; Filipe, Mario; Marques, Sara; Salgueiro, Ana-Marisa; Becker, Jorg D.; Belo, Jose AntonioDuring early vertebrate development, the correct establishment of the body axes is critical. The anterior pole of the mouse embryo is established when Distal Visceral Endoderm (DVE) cells migrate to form the Anterior Visceral Endoderm (AVE). Symmetrical expression of Lefty1, Cer1 and Dkk1 determines the direction of DVE migration and the future anterior side. In addition to the establishment of the Anterior-Posterior axis, the AVE has also been implicated in anterior neural specification. To better understand the role of the AVE in these processes, we have performed a differential screening using Affymetrix GeneChip technology with AVE cells isolated from cer1P-EGFP transgenic mouse embryos. We found 175 genes which were upregulated in the AVE and 36 genes in the Proximal-posterior sample. Using DAVID software, we characterized the AVE cell population regarding cellular component, molecular function and biological processes. Among the genes that were found to be upregulated in the AVE, several novel genes were identified. Four of these transcripts displaying high-fold change in the AVE were further characterized by in situ hybridization in early stages of development in order to validate the screening. From those four selected genes, one, denominated Adtk1, was chosen to be functionally characterized by targeted inactivation in ES cells. Adtk1 encodes for a serine/threonine kinase. Adtk1 null mutants are smaller and present short limbs due to decreased mineralization, suggesting a potential role in chondrogenesis during limb development. Taken together, these data point to the importance of reporting novel genes present in the AVE.