Over the past three decades, molecular genetic studies have revealed some critical mutations underlying the pathogenesis of the sporadic and inherited forms of colorectal cancer (CRC). A relatively limited number of oncogenes and tumor-suppressor genes-most prominently the APC, KRAS, and p53 genes-are mutated in a sizeable fraction of CRCs, and a larger collection of genes that are mutated in subsets of CRC have begun to be defined. Together with DNA-methylation and chromatin-structure changes, the mutations act to dysregulate conserved signaling networks that exert context-dependent effects on critical cell phenotypes, including the regulation of cellular metabolism, proliferation, differentiation, and survival. Much work remains to be done to fully understand the nature and significance of the individual and collective genetic and epigenetic defects in CRC. Some key concepts for the field have emerged, two of which are emphasized in this review. Specifically, the gene defects in CRC often target proteins and pathways that exert pleiotropic effects on the cancer cell phenotype, and particular genetic and epigenetic alterations are linked to biologically and clinically distinct subsets of CRC.
Research on the interaction between plants and microbes has attracted considerable attention in recent years. The use of modem genetic techniques has now made possible a detailed analysis both of plant and of microbial genes involved in phytopathogenic and beneficial interactions. At the biochemical level, signal molecules and their receptors, either of plant or of microbial origins, have been detected which act in signal transduction pathways or as co-regulators of gene expression. We begin to understand the molecular basis of classical concepts such as gene-for-gene relationships, hypersensitive response, induced resistance, to name just a few. We realize, and will soon exploit, the tremendous potential of the results of this research for practical application, in particular to protect crop plants against diseases and to increase crop yield and quality. This exclung field of research, which is also of truly interdisciplinary nature, is expanding rapidly. A Symposium series has been devoted to it which began in 1982. Recently, the 5th International Symposium on the Molecular Genetics of Plant-Microbe Interactions was held in Interlaken, Switzerland. It brought together 640 scientists from almost 30 different countries who reported their latest research progress in 47 lectures, 10 short oral presentations, and on over 400 high-quality posters. This book presents a collection of papers that comprehensively reflect the major areas under study, explain novel experimental approaches currently in use, highlight significant advances made over the last one or two years but also emphasize the obstacles still ahead of us.