Agrobacterium rhizogenes rolB oncogene: An intriguing player for many roles.

The rolB oncogene is one of the so-called rol genes found in the T-DNA region of the Agrobacterium rhizogenes Ri plasmid and involved in the hairy root syndrome, a tumour characterized by adventitious root overgrowth on plant stem. rolB produces in plants a peculiar phenotype that, together with its root-inducing capacity, has been connected to auxin sensitivity. The gene is able to modify the plant genetic programme to induce meristem cells and direct them to differentiate not only roots, but also other cells, tissues or organs. Besides its essential function in hairy root pathogenesis, the rolB role has been progressively extended to cover several physiological aspects in the transgenic plants: from secondary metabolites production and ROS inhibition, to abiotic and biotic stress tolerance and photosynthesis improvement. Some of the observed effects could be determined, at least in part, through microRNAs molecules, suggesting an epigenetic control rolB-mediated. These multifaceted capacities could allow plants to withstand adverse environmental conditions, enhancing fitness. In spite of this expanding knowledge, functional analyses did not detect yet any definitive rolB-derived biochemical product, even if more than one enzymatic activity has been ascribed to it. Moreover, phylogenetic and evolutionary studies evidenced no homology with any plant sequences but, otherwise, it belongs to the Plast family, a group of rolB-homologous bacterial genes. Finally, the finding of sequences similar to rolB in plants not infected by A. rhizogenes suggests a hypothetical plant origin for this gene, implying different possibilities about its evolution.

Sirtinol treatment reduces inflammation in human dermal microvascular endothelial cells.

Histone deacetylases (HDAC) are key enzymes in the epigenetic control of gene expression. Recently, inhibitors of class I and class II HDAC have been successfully employed for the treatment of different inflammatory diseases such as rheumatoid arthritis, colitis, airway inflammation and asthma. So far, little is known so far about a similar therapeutic effect of inhibitors specifically directed against sirtuins, the class III HDAC. In this study, we investigated the expression and localization of endogenous sirtuins in primary human dermal microvascular endothelial cells (HDMEC), a cell type playing a key role in the development and maintenance of skin inflammation. We then examined the biological activity of sirtinol, a specific sirtuin inhibitor, in HDMEC response to pro-inflammatory cytokines. We found that, even though sirtinol treatment alone affected only long-term cell proliferation, it diminishes HDMEC inflammatory responses to tumor necrosis factor (TNF)α and interleukin (IL)-1ß. In fact, sirtinol significantly reduced membrane expression of adhesion molecules in TNFã- or IL-1ß-stimulated cells, as well as the amount of CXCL10 and CCL2 released by HDMEC following TNFα treatment. Notably, sirtinol drastically decreased monocyte adhesion on activated HDMEC. Using selective inhibitors for Sirt1 and Sirt2, we showed a predominant involvement of Sirt1 inhibition in the modulation of adhesion molecule expression and monocyte adhesion on activated HDMEC. Finally, we demonstrated the in vivo expression of Sirt1 in the dermal vessels of normal and psoriatic skin. Altogether, these findings indicated that sirtuins may represent a promising therapeutic target for the treatment of inflammatory skin diseases characterized by a prominent microvessel involvement.

The rolD oncogene promotes axillary bud and adventitious root meristems in Arabidopsis.

The expression of the Agrobacterium rhizogenes rolD oncogene induces precocious floral transition and strong flowering potential in tobacco and tomato. Here, we describe specific developmental effects induced by expression of rolD in Arabidopsis. We show that floral transition, as histologically monitored, occurred in rolD- plants earlier than in wild type, and this was coupled with a premature and enhanced formation of vegetative and reproductive axillary bud meristems. Furthermore, CYP79F1/SUPERSHOOT/BUSHY (SPS), a gene that negatively controls shoot branching in Arabidopsis and involved in glucosinolate metabolism and in cytokinin and auxin homeostasis, was down-regulated in rolD plants. The multiplication of post-embryonic meristems was also observed in the root system, with enhanced adventitious root formation. This result was confirmed by thin cell layer response in vitro, both under hormone-free and standard rooting conditions. However, the formation of lateral root meristems was not affected by rolD expression. Our results show that rolD accelerates and enhances specific post-embryonic meristems in Arabidopsis.