Synergies and trade-offs between insect and pathogen resistance in maize leaves and roots

Determining links between plant defence strategies is important to understand plant evolution and to optimize crop breeding strategies. Although several examples of synergies and trade-offs between defence traits are known for plants that are under attack by multiple organisms, few studies have attempted to measure correlations of defensive strategies using specific single attackers. Such links are hard to detect in natural populations because they are inherently confounded by the evolutionary history of different ecotypes. We therefore used a range of 20 maize inbred lines with considerable differences in resistance traits to determine if correlations exist between leaf and root resistance against pathogens and insects. Aboveground resistance against insects was positively correlated with the plant's capacity to produce volatiles in response to insect attack. Resistance to herbivores and resistance to a pathogen, on the other hand, were negatively correlated. Our results also give first insights into the intraspecific variability of root volatiles release in maize and its positive correlation with leaf volatile production. We show that the breeding history of the different genotypes (dent versus flint) has influenced several defensive parameters. Taken together, our study demonstrates the importance of genetically determined synergies and trade-offs for plant resistance against insects and pathogens.

[Possible genetic link between Darier's disease and depression : Review of the literature and case history.]

Darier's disease is a rare, inherited autosomal dominant skin disorder caused by a mutation in the sarcoendoplasmatic reticulum calcium transporter (SERCA)-2-gene. In a number of pedigrees, Darier's disease closely relates with affective disorder. The most likely hypothesis for this is a susceptibility gene for affective disorder near the SERCA-2-gene. A 6.5-megabase region could be identified as a susceptibility locus. This region constitutes a susceptability locus also in affective disorder without Darier's disease. The underlying gene has not yet been identified.