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This article is from BMC Plant Biology , volume 13 . Abstract Background: During plant tissue morphogenesis cells have to coordinate their behavior to allow the generation of the size, shape and cellular patterns that distinguish an organ. Despite impressive progress the underlying signaling pathways remain largely unexplored. In Arabidopsis thaliana, the atypical leucine-rich repeat receptor-like kinase STRUBBELIG (SUB) is involved in signal transduction in several developmental processes including the formation of carpels, petals, ovules and root hair patterning. The three STRUBBELIG-LIKE MUTANT (SLM) genes DETORQUEO (DOQ), QUIRKY (QKY) and ZERZAUST (ZET) are considered central elements of SUB-mediated signal transduction pathways as corresponding mutants share most phenotypic aspects with sub mutants. Results: Here we show that DOQ corresponds to the previously identified ANGUSTIFOLIA gene. The genetic analysis revealed that the doq-1 mutant exhibits all additional mutant phenotypes and conversely that other an alleles show the slm phenotypes. We further provide evidence that SUB and AN physically interact and that AN is not required for subcellular localization of SUB. Conclusions: Our data suggest that AN is involved in SUB signal transduction pathways. In addition, they reveal previously unreported functions of AN in several biological processes, such as ovule development, cell morphogenesis in floral meristems, and root hair patterning. Finally, SUB and AN may directly interact at the plasma membrane to mediate SUB-dependent signaling.

We propose a three dimensional mechanical model of embryonic tissue dynamics. Mechanically coupled adherent cells are represented as particles interconnected with elastic beams which can exert non-central forces and torques. Tissue plasticity is modeled by a stochastic process consisting of a connectivity change (addition or removal of a single link) followed by a complete relaxation to mechanical equilibrium. In particular, we assume that (i) two non-connected, but adjacent particles can form a new link; and (ii) the lifetime of links is reduced by tensile forces. We demonstrate that the proposed model yields a realistic macroscopic elasto-plastic behavior and we establish how microscopic model parameters affect the material properties at the macroscopic scale. Based on these results, microscopic parameter values can be inferred from tissue thickness, macroscopic elastic modulus and the magnitude and dynamics of intercellular adhesion forces. In addition to their mechanical role, model particles can also act as active simulation agents and modulate their connectivity according to specific rules. As an example, anisotropic link insertion and removal probabilities can give rise to local cell intercalation and large scale convergent extension movements. The proposed stochastic simulation of cell activities yields fluctuating tissue movements which exhibit the same autocorrelation properties as empirical data from avian embryos.

Lectures given during a joint meeting of the Belgian Plant and Tissue Culture Group BPTCG and the FWO Research Network Plant Morphogenesis held in the Arenberg Castle, KUL, Leuven, December 6, 1996. Contributions include aspects of plant modelling, leaf and flower development and somatic embryogenis, highlighting mathematical, biophysiological, genetic and molecular approaches

1Letters of Lord Nelson to Lady Hamilton, Volume I

By Horatio Nelson

Horatio Nelson, 1st Viscount Nelson, 1st Duke of Bronté, KB (29 September 1758 – 21 October 1805) was an English flag officer famous for his service in the Royal Navy, particularly during the Napoleonic Wars. He won several victories, including the Battle of Trafalgar in 1805, during which he was killed. These are the letters that he wrote to Lady Hamilton, with whom he was having a notorious affair until his death in 1805. (Summary by Wikipedia)

2Letters of Lord Nelson to Lady Hamilton, Volume II

By Horatio Nelson

Horatio Nelson, 1st Viscount Nelson, 1st Duke of Bronté, KB (29 September 1758 – 21 October 1805) was an English flag officer famous for his service in the Royal Navy, particularly during the Napoleonic Wars. He won several victories, including the Battle of Trafalgar in 1805, during which he was killed. These are the letters that he wrote to Lady Hamilton, with whom he was having a notorious affair until his death in 1805. (Summary by Wikipedia)

3Fox That Wanted Nine Golden Tails

By Kathleen Gray Nelson

A fox aspires to reach his 1000th birthday safely and be rewarded with nine golden tails in this wise and charming fairytale.

4Silver Chimes in Syria: Glimpses of a Missionary's Experiences

By William S. Nelson

William S. Nelson, D.D., was appointed as a missionary to Syria by the Board of Foreign Missions of the Presbyterian Church, USA in 1888. In this short works, as the title suggests, he gives glimpses into his life as a missionary against the background of Syrian culture.