Patterns of mitochondrial DNA instability in Brassica campestris cultured cells

We previously showed that the mitochondrial DNA (mtDNA) of a Brassica campestris callus culture had undergone extensive rearrangements (i.e. large inversions and a duplication) relative to DNA of the control plant [54]. In this study we observed that after continued growth, the mtDNA of this culture continues to change, with rearranged forms amplifying and diminishing to varying proportions. Strikingly similar changes were detected in the mtDNA profiles of a variety of other long- and short-term callus and cell suspension lines. However, the proportions of parental (‘unrearranged’) and novel (‘rearranged’) forms varied in different cultured cell mtDNAs. To address the source of this heterogeneity, we compared the mtDNA organization of 28 individual plants from the parental seed stock. With the exception of one plant containing high levels of a novel plasmid-like mtDNA molecule, no significant variation was detected among individual plants and therefore source plant variation is unlikely to have contributed to the diversity of mitochondrial genomes observed in cultured cells. The source of this culture-induced heterogeneity was also investigated in 16 clones derived from single protoplasts. A mixed population of unrearranged and rearranged mtDNA molecules was apprent in each protoclone, suggesting that the observed heterogeneity in various cultures might reflect the genomic composition of each individual cell; however, the induction of an intercellular heterogeneity subsequent to the protoplast isolation was not tested and therefore cannot be ruled out. The results of this study support our earlier model that the rapid structural alteration of B. campestris mtDNA in vitro results from preferential amplification and reassortment of minor pre-existing forms of the genome rather than de novo rearrangement. Infrequent recombination between short dispersed repeated elements is proposed as the underlying mechanism for the formation of these minor mtDNA molecules.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43428/1/11103_2004_Article_BF00017914.pd

How Collaboration Software Enables Globally Distributed Software Development Teams to Become Agile - An Effective Use Perspective

Offshored, distributed teams increasingly use agile software development methodologies. Since agile software development practices were originally developed for co-located teams, distributed teams are required to use tools in order to achieve agility. This study is the first to adopt the lens of effective use theory in order to explore the role of tools in achieving agility, and other favorable project outcomes despite geographic distribution. First, we present Effective Use Theory and contextualize it for outsourced, agile software development projects. After this contextualization of Effective Use Theory, we present our exploratory, longitudinal case study and the four data sources we will use as a basis for our empirical investigation. Then, we develop measures that will enable us to study effective use behaviors empirically for the first time. The paper Ends with expected results and implications for literature on IS outsourcing, agile software development, tool use literature, and for managerial practice