The rolC gene of agrobacteria: towards the understanding of its functions

Agrobacterium rhizogenes Conn is a soil bacterium, which can transform plants by inserting a plasmid fragment into the plant genome. This fragment contains a “root locus”: four genes that cause root overgrowth of the transformed plant, the so-called “hairy root syndrome”. The most studied gene of the root locus is rolC. For more than 30 years of research on this gene, data have been obtained on its expression, protein localization and putative functions of the protein as well as on its effect on plant morphology and biochemistry. The rolC transformation leads to multiple morphological effects, most common among which are dwarfism, bushiness, and a change in the shape of the leaf blade. Such specific plant reactions are associated with changes in hormone balance under the influence of rolC. The levels of auxins, cytokinins, and abscisic acid do change in transformed plants, but no regularities have been revealed. Also, the signaling pathways of rolC affecting the hormonal system of plants are not established. Morphogenetic effects can occur in varying degrees depending on the promoter under which the rolC works. A constitutive promoter usually leads to a more pronounced effect when compared to a gene that operates under a native promoter. Secondary plant metabolism is also affected by rolC. The synthesis of various metabolites is amplified in transformants, and, in contrast to morphological effects, this biochemical effect does not depend on the promoter. Some secondary metabolites are associated with the plant defense system; thus, rolC is able to indirectly influence this aspect of plant physiology. This review summarizes the results of the rolC gene studies in plants. The authors formulate the main hypotheses regarding the mechanisms of the gene in order to promote our understanding of its function in plants.

Progress and Applications of Polyphosphate in Bone and Cartilage Regeneration

Patients with bone and cartilage defects due to infection, tumors, and trauma are quite common. Repairing bone and cartilage defects is thus a major problem for clinicians. Autologous and artificial bone transplantations are associated with many challenges, such as limited materials and immune rejection. Bone and cartilage regeneration has become a popular research topic. Inorganic polyphosphate (polyP) is a widely occurring biopolymer with high-energy phosphoanhydride bonds that exists in organisms from bacteria to mammals. Much data indicate that polyP acts as a regulator of gene expression in bone and cartilage tissues and exerts morphogenetic effects on cells involved in bone and cartilage formation. Exposure of these cells to polyP leads to the increase of cytokines that promote the differentiation of mesenchymal stem cells into osteoblasts, accelerates the osteoblast mineralization process, and inhibits the differentiation of osteoclast precursors to functionally active osteoclasts. PolyP-based materials have been widely reported in in vivo and in vitro studies. This paper reviews the current cellular mechanisms and material applications of polyP in bone and cartilage regeneration.

Morphozoic, Cellular Automata with Nested Neighborhoods as a Metamorphic Representation of Morphogenesis

A cellular automaton model, Morphozoic, is presented. Morphozoic may be used to investigate the computational power of morphogenetic fields to foster the development of structures and cell differentiation. The term morphogenetic field is used here to describe a generalized abstraction: a cell signals information about its state to its environment and is able to sense and act on signals from nested neighborhood of cells that can represent local to global morphogenetic effects. Neighborhood signals are compacted into aggregated quantities, capping the amount of information exchanged: signals from smaller, more local neighborhoods are thus more finely discriminated, while those from larger, more global neighborhoods are less so. An assembly of cells can thus cooperate to generate spatial and temporal structure. Morphozoic was found to be robust and noise tolerant. Applications of Morphozoic presented here include: 1) Conway's Game of Life, 2) Cell regeneration, 3) Evolution of a gastrulation-like sequence, 4) Neuron pathfinding, and 5) Turing's reaction-diffusion morphogenesis.