Paternally inherited transgenes are down-regulated but retain low activity during early embryogenesis in Arabidopsis.

We investigated the timing of transgene activation after fertilisation in Arabidopsis following crosses and using two transgenic promoters (from the AtCYCB1 and AtLTP1 genes). Using both a transactivation system and direct transcriptional fusion to drive beta-glucuronidase reporter expression, reciprocal crosses showed a lack of expression of the paternal components. This is consistent with a lack of paternal genome activity previously reported during early seed development in Arabidopsis [Viella-Calzada et al. (2000) Nature 404, 91-94]. However, transactivation experiments of the BARNASE gene gave evidence that at least some paternal loci retain transcriptional activity, though at a low level, during early embryogenesis.

The maternal to zygotic transition in animals and plants.

In the animal kingdom, maternal control of early development is a common feature. The onset of zygotic control over early development, defined as the maternal to zygotic transition (MZT), follows fertilization with a delay of a variable number of cell divisions, depending on the species. The MZT has been well defined in animals, but investigations remain in their infancy in plants. Recent evidence suggests, however, that in plants as in animals, the MZT also occurs several division cycles after fertilization. The likely convergent evolution of the MZT in the animal and plant kingdoms is fascinating and raises major questions regarding its biological significance, particularly with regard to its importance in genome reprogramming and the acquisition of totipotency by the embryo.

[Clinical factors favoring excessive subconjunctival fibroblastic proliferation after glaucoma surgery]. / Facteurs cliniques favorisant la cicatrisation conjonctivale excessive après chirurgie du glaucome.

PURPOSE: To understand risk factors for failure of glaucoma filtering surgery. PATIENTS: A retrospective study of 67 eyes (16 nonpenetrating trabeculectomies, 51 trabeculectomies [31 with 5FU and 20 with mitomycin]) of 61 patients in whom 5FU bleb revision was needed because of increasing intraocular pressure. Postoperative incidents were analyzed to explain excessive subconjunctival fibroblastic proliferation. RESULTS: In eight cases, IOP increased after 6.16 months (+/-2) and for 59 eyes, after 33.5 days after surgery (+/-11.4). Postoperative incidents were 24 (35.9%) bleb leaks, nine cases (13.4%) of hypotony with choroidal detachment, six (9.0%) iris incarcerations, seven (10.4%) cystic blebs, and 21 (31.3%) inflammatory flat blebs. After a mean follow-up of 27 months +/- 18, the success of bleb 5FU revision was 84.6% for nonpenetrating trabeculectomy (without glaucoma treatment, 69.2%; with medical treatment, 15.4%) and 73.9% for trabeculectomy (47.8% and 32.6%). CONCLUSION: Postoperative outcomes favor an inner or outer obstacle to conjunctival filtration. Aqueous humor can no longer remain in the subconjunctival spaces, increasing the risk of glaucoma surgery failure. Early follow-up of glaucoma surgery is crucial to obtaining long-lasting filtration.

Transactivation of BARNASE under the AtLTP1 promoter affects the basal pole of the embryo and shoot development of the adult plant in Arabidopsis.

Genetically controlled expression of a toxin provides a tool to remove a specific structure and consequently study its role during a developmental process. The availability of many tissue-specific promoters is a good argument for the development of such a strategy in plants. We have developed a conditional system for targeted toxin expression and demonstrated its use for generating embryo phenotypes that can bring valuable information about signalling during embryogenesis. The BARNASE gene was expressed in the Arabidopsis embryo under the control of two promoters, one from the cyclin AtCYCB1 gene and one from the AtLTP1 gene (Lipid Transfer Protein 1). One-hundred percent seed abortion was obtained with the cyclin promoter. Surprisingly however, the embryos displayed a range of lethal phenotypes instead of a single arrested stage as expected from this promoter. We also show that BARNASE expression under the control of the AtLTP1 promoter affects the basal pole of the globular embryo. Together with reporter expression studies, this result suggests a role of the epidermis in controlling the development of the lower tier of the embryo. This defect was not embryo-lethal and we show that the seedlings displayed a severe shoot phenotype correlated to epidermal defects. Therefore, the epidermis does not play an active role during organogenesis in seedlings but is important for the postgermination development of a viable plant.