Rudi Appels - Böcker

The potato (Solanum tuberosum L. ) tuber is a major food source in many countries of the world, and subsequently potato has been the target of a good deal of effort directed at engineering disease and herbicide tolerance, and improvements in various crop characteristics. Consequently investigations into the regulation of gene expression in tubers is relevant to these endeavours, as tubers are the main target organ for modification of gene expression. We have been interested in the regulation of genes in tubers for these reasons. Morphologically tubers are modified stems, which have enlarged radially by limited cell division and substantial expansion. At the molecular level, tuber development is characterised by a massive increase in starch deposition and the synthesis of a limited number of abundant proteins. These include proteinase inhibitors and a 40kd group of proteins called patatin, which are acyl hydrolases. Together these proteins account for over 50% of tuber proteins (reviewed by Bevan, 1991). The synthesis of these proteins has parallels to the synthesis of other somatic storage proteins, especially the VSP proteins of soybean. In both potato and soybean, removal of the sink for these proteins (tubers and pods, respectively) causes deposition in other tissues (Staswick, 1990). It is hypothesised that transcriptional control of the genes encoding these proteins is regulated in part by source-sink relationships of metabolites or other factors. In the case of VSPs, both amino acid levels and jasmonic acid play a major regulatory role (Staswick et aI.

This book should be of interest to students of genetics, botany, agronomy, plant science, crop science, plant breeding, entomology, animal science and human genetics.

A Historical Perspective on the Study of Chromosome Structure and Function R. Appels Division of Plant Industry CSIRO P.O. Box 1600 A.C.T. AUSTRALIA "Modern physical science gives us no model to explain the re­ duplication of the gene-string in each cell generation, or to ex­ plain the production of effective quantities of specific enzymes or other agents by specific genes. The precise pairing and inter­ change of segments by homologous gene-strings at meiosis also suggest novel physical properties of this form of matter". Stadler (1954) The very strong influence of reductionism in the history of understanding chromosome structure and function is evident in the above quotation from Stadler's 1954 paper, "The gene". Earlyob­ servations on the constancy of the cytological appearance of chromo­ somes and their regular behaviour in cell division led to specula­ tion on their biological importance. As genetics became more refined in the early decades of the 20th century the genes-on-a­ string model of chromosomes developed and greater emphasis was placed on the further dissection of these structures. As a result, in the 1980's the reductionist approach is reaching a crest as extensive regions of the genetic material are being sequenced.

Chromosome biology has been brought to a golden age by phenomenal advanced in molecular genetics and techniques. This is true in the plant arena, and it is becoming increasingly true in animal studies, where chromosomes are more difficult to work with.

The potato (Solanum tuberosum L. ) tuber is a major food source in many countries of the world, and subsequently potato has been the target of a good deal of effort directed at engineering disease and herbicide tolerance, and improvements in various crop characteristics. Consequently investigations into the regulation of gene expression in tubers is relevant to these endeavours, as tubers are the main target organ for modification of gene expression. We have been interested in the regulation of genes in tubers for these reasons. Morphologically tubers are modified stems, which have enlarged radially by limited cell division and substantial expansion. At the molecular level, tuber development is characterised by a massive increase in starch deposition and the synthesis of a limited number of abundant proteins. These include proteinase inhibitors and a 40kd group of proteins called patatin, which are acyl hydrolases. Together these proteins account for over 50% of tuber proteins (reviewed by Bevan, 1991). The synthesis of these proteins has parallels to the synthesis of other somatic storage proteins, especially the VSP proteins of soybean. In both potato and soybean, removal of the sink for these proteins (tubers and pods, respectively) causes deposition in other tissues (Staswick, 1990). It is hypothesised that transcriptional control of the genes encoding these proteins is regulated in part by source-sink relationships of metabolites or other factors. In the case of VSPs, both amino acid levels and jasmonic acid play a major regulatory role (Staswick et aI.