Plants as resource mosaics: a functional model for predicting patterns of within-plant resource heterogeneity to consumers based on vascular architecture and local environmental variability

Plant characteristics that determine food quantity and quality to consumers exhibit extensive within-plant heterogeneity, and this heterogeneity is an important influence on the interactions between plants and consumers (herbivores, pathogens, mutualists, soil-dwelling microorganisms). Here we present a functional model – based on plant vascular architecture and local environmental variability – that can be used to predict the patterns of within-plant resource heterogeneity. We argue that heterogeneity is generated largely by sectoriality, the restricted movement of resources along vascular traces within a plant. In essence, the combination of sectoriality and spatial variation in previous damage, nutrient, water, and light availability generates predictable patterns of within-plant heterogeneity in tissue quality. We point out that vascular architecture differs across taxa, growth habit and plant developmental stage, and suggest that certain attributes of the environment maximize the extent of heterogeneity.     

Disruption of chromosome 11 in canine fibrosarcomas highlights an unusual variability of CDKN2B in dogs

Background  

In dogs in the western world neoplasia constitutes the most frequently diagnosed cause of death. Although there appear to be similarities between canine and human cancers, rather little is known about the cytogenetic and molecular alterations in canine tumours. Different dog breeds are susceptible to different types of cancer, but the genetic basis of the great majority of these predispositions has yet to be discovered. In some retriever breeds there is a high incidence of soft tissue sarcomas and we have previously reported alterations of chromosomes 11 and 30 in two poorly differentiated fibrosarcomas. Here we extend our observations and present a case report on detail rearrangements on chromosome 11 as well as genetic variations in a tumour suppressor gene in normal dogs.     

Using hybrid systems to explore the evolution of tolerance to damage

Hybridization is common and important to the adaptive evolution of plants. Hybridization has resulted in the formation of new species and the introgression of traits between species. This paper discusses the advantages of using hybrid systems to explore the evolution of tolerance to herbivore damage (i.e., the ability to diminish the negative effects of damage on fitness). The major consequence of hybridization likely to make it influential for tolerance evolution is that hybridization generates broad variation in traits that can be selected for or against. In addition to generating greater variation in tolerance to damage and its putative traits (e.g., traits associated with allocation patterns and meristem production), hybridization can generate greater independence among tolerance traits and between tolerance and defense traits. Greater independence may provide a greater ability to discern mechanisms of tolerance, give a greater probability of detecting allocation costs of tolerance, and provide an effective means to evaluate tradeoffs between tolerance and defense. Interspecific hybrid systems can also be used to evaluate the importance of co-adaptation of tolerance traits. Moreover, recombinant hybrids can be used in selection studies focusing on tolerance to damage to discern whether parental combinations of tolerance traits are favored over novel combinations. Research in hybrid systems that investigate the selective importance of tolerance, the patterns of inheritance of tolerance traits, and the genetic architecture of plant species involved can be vital to our evaluation of the adaptive role of tolerance to damage. This revised version was published online in July 2006 with corrections to the Cover Date.     

The genetic basis for variation in the concentration of phenolic glycosides in Salix sericea: an analysis of heritability

Willows and many other members of the Salicaceae often produce phenolic glycosides, and the concentrations of these are known to vary among plants. We used progeny from a factorial half-sib quantitative genetics experiment with Salix sericea to determine whether the concentration of two phenolic glycosides, salicortin and 2′-cinnamoylsalicortin, show additive heritability. We found that the concentration of salicortin was much higher than 2′-cinnamoylsalicortin, and that both compounds showed additive genetic variation. However, the heritability of these two chemicals differed dramatically. We obtained heritability values of 0.20 for salicortin and 0.59 for 2′-cinnamoylsalicortin. Plant growth parameters were not strongly correlated with the concentrations of these phenolic glycosides.     

Functional implications of the microbial community structure of undefined mesophilic starter cultures

This review describes the recent advances made in the studies of the microbial community of complex and undefined cheese starter cultures. We report on work related to the composition of the cultures at the level of genetic lineages, on the presence and activity of bacteriophages and on the population dynamics during cheese making and during starter culture propagation. Furthermore, the link between starter composition and starter functionality will be discussed. Finally, recent advances in predictive metabolic modelling of the multi-strain cultures will be discussed in the context of microbe-microbe interactions.