Submitted to: Genome
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/12/2002
Publication Date: 4/1/2003
Citation: CORTEZ-CRUZ, M., SNOOK, M.E., MCMULLEN, M.D. THE GENETIC BASIS OF C-GLYCOSYL FLAVONE B-RING MODIFICATION IN MAIZE (ZEA MAYS L.) SILKS. GENOME. 2003. v. 46. p. 182-194. Interpretive Summary: Differential response of crop plant varieties to biotic stress often involves the specific synthesis of chemical compounds. Understanding the genetic basis for the differential synthesis of related chemicals with anti-microbial or anti-insect activity would improve efforts to breed yield-stable crops. In this manuscript, we demonstrate that the genetic control of related compounds with activity against the corn earworm works not by controlling the number of additional enzyme reactions by rather by altering the dynamics of the entire biochemical pathways involved. These results are significant for scientists thinking about metabolic engineering for improved biotic stress resistance. Instead of adding a few enzyme reactions to existing pathways, one needs to consider altering flow of chemicals between and through interconnected pathways to obtain the desired enhancement of plant resistance.
Technical Abstract: Resistance to corn earworm (Helicoverpa zea Boddie) has been attributed to high concentrations of C-glycosyl flavones and chlorogenic acid in maize (Zea mays L.) silks. The most common C-glycosyl flavones isolated from maize silks are maysin, apimaysin, and methoxymaysin, which are distinguished by their B-ring substitutions. For a better understanding of the genetic mechanisms underlying the synthesis of these compounds, we conducted a quantitative trait locus (QTL) study with two populations. For chlorogenic acid, maysin, and methoxymaysin concentration, the major QTL for both populations was located on chromosome 4 near umc1963. For apimaysin, the major QTL in both populations was located at the position of the pr1 locus on chromosome 5. The QTL alleles on chromosome 4 that increased the synthesis of methoxymaysin significantly decreased the synthesis of maysin and chlorogenic acid. This decrease in maysin concentration was four-fold greater than the increase in methoxymaysin. Our results indicate that the QTL on chromosome 4, responsible for the increase in methoxymaysin synthesis, alters the dynamics of both the phenylpropanoid and flavonoid pathways.