This proposed research represents a unique combination of technologies and subsequent opportunity to examine the molecular basis of traits exhibiting quantitative expression and inheritance. It has been observed that there are often strong associations between patterns of variation of isozyme markers and plant morphological characters which show quantitative inheritance. Recently, Helentjaris, Edwards, and Stuber (unpublished data) have extended this type of analysis using restriction fragment length polymorphisms (RFLP). Several RFLP loci were identified which were predictive for plant height. Robertson has suggested that genetic loci resulting in dwarf plants are good candidates for loci involved in the quantitative inheritance of plant height. The dwarf locus, d3, maps in one of the areas of the genome identified as significantly contributing to plant height. We propose to take advantage of this easily recognizable phenotype to clone a dwarf allele using the strategy of insertion mutagenesis with a transposable element. The application of RFLP analysis to quantitative traits, specifically plant height, has initiated the examination of this phenomenon at the DNA level. Extending the analysis by cloning through transposable element tagging will allow direct examination of gene expression.Applications:When successful, the proposed research will have developed methods by which major genes involved in the expression of quantitative traits can be localized and cloned. Additionally, cloning of plant height quantitative trait loci could prove to be of interest for genetic manipulation in other crops by genetic engineering, especially if they involve genes regulating hormone synthesis or response. It is assumed that there is conservation of function and structure of these pathways. If this is true, then the research on maize may develop the most efficient system to first obtain these genes before progressing on to isolating them from other species.
