Pseudomonas syringae Catalases Are Collectively Required for Plant Pathogenesis.

The bacterial pathogen Pseudomonas syringae pv. tomato DC3000 must detoxify plant-produced hydrogen peroxide (H(2)O(2)) in order to survive in its host plant. Candidate enzymes for this detoxification include the monofunctional catalases KatB and KatE and the bifunctional catalase-peroxidase KatG of DC3000. This study shows that KatG is the major housekeeping catalase of DC3000 and provides protection against menadione-generated endogenous H(2)O(2). In contrast, KatB rapidly and substantially accumulates in response to exogenous H(2)O(2). Furthermore, KatB and KatG have nonredundant roles in detoxifying exogenous H(2)O(2) and are required for full virulence of DC3000 in Arabidopsis thaliana. Therefore, the nonredundant ability of KatB and KatG to detoxify plant-produced H(2)O(2) is essential for the bacteria to survive in plants. Indeed, a DC3000 catalase triple mutant is severely compromised in its ability to grow in planta, and its growth can be partially rescued by the expression of katB, katE, or katG. Interestingly, our data demonstrate that although KatB and KatG are the major catalases involved in the virulence of DC3000, KatE can also provide some protection in planta. Thus, our results indicate that these catalases are virulence factors for DC3000 and are collectively required for pathogenesis.

Little ROCK is a ROCK1 pseudogene expressed in human smooth muscle cells.

BACKGROUND: Sequencing of the human genome has identified numerous chromosome copy number additions and subtractions that include stable partial gene duplications and pseudogenes that when not properly annotated can interfere with genetic analysis. As an example of this problem, an evolutionary chromosome event in the primate ancestral chromosome 18 produced a partial duplication and inversion of rho-associated protein kinase 1 (ROCK1 -18q11.1, 33 exons) in the subtelomeric region of the p arm of chromosome 18 detectable only in humans. ROCK1 and the partial gene copy, which the gene databases also currently call ROCK1, include non-unique single nucleotide polymorphisms (SNPs). RESULTS: Here, we characterize this partial gene copy of the human ROCK1, termed Little ROCK, located at 18p11.32. Little ROCK includes five exons, four of which share 99% identity with the terminal four exons of ROCK1 and one of which is unique to Little ROCK. In human while ROCK1 is expressed in many organs, Little ROCK expression is restricted to vascular smooth muscle cell (VSMC) lines and organs rich in smooth muscle. The single nucleotide polymorphism database (dbSNP) lists multiple variants contained in the region shared by ROCK1 and Little ROCK. Using gene and cDNA sequence analysis we clarified the origins of two non-synonymous SNPs annotated in the genome to actually be fixed differences between the ROCK1 and the Little ROCK gene sequences. Two additional coding SNPs were valid polymorphisms selectively within Little ROCK. Little ROCK-Green Fluorescent fusion proteins were highly unstable and degraded by the ubiquitin-proteasome system in vitro. CONCLUSION: In this report we have characterized Little ROCK (ROCK1P1), a human expressed pseudogene derived from partial duplication of ROCK1. The large number of pseudogenes in the human genome creates significant genetic diversity. Our findings emphasize the importance of taking into consideration pseudogenes in all candidate gene and genome-wide association studies, as well as the need for complete annotation of human pseudogenome.

Loss of the retinoblastoma tumor suppressor protein in murine calvaria facilitates immortalization of osteoblast-adipocyte bipotent progenitor cells characterized by low expression of N-cadherin.

The retinoblastoma gene, RB1, is frequently inactivated in a subset of tumors, including retinoblastoma and osteosarcoma (OS). One characteristic of OS, as well as other tumors in which RB1 is frequently inactivated, is the lack of N-cadherin-mediated cell-cell adhesions. The frequent inactivation of RB1 and parallel loss of N-cadherin expression in OS prompted us to ask whether these observations are directly related to each other. In this study, we observed reduced N-cadherin expression in RB1(-/-) calvarial osteoblasts. In addition, RB1(-/-) cell lines had increased migration potential compared to their RB1(+/+) counterparts. These properties of RB1(-/-) cell lines correlated with an adipogenic potential lacking in RB1(+/+) cell lines, suggesting that each property is present in an immature progenitor cell. The isolation of a cell population with low surface expression of N-cadherin and enhanced adipogenic ability supports this view. Interestingly, the acute loss of pRb does not affect N-cadherin expression or migration or confer adipogenic potential to immortalized RB1(+/+) calvarial cells, suggesting that these traits are not a direct consequence of pRb loss; rather, pRb loss leads to the expansion and immortalization of an immature progenitor pool characterized by these properties.