Characterization of gene expression profile associated with energy restriction-induced cold tolerance of heart

SwoHp, a nucleoside diphosphate kinase, is essential in Aspergillus nidulans

The temperature-sensitive swoH1 mutant of Aspergillus nidulans was previously identified in a screen for mutants with defects in polar growth. In the present work, we found that the swoH1 mutant swelled, lysed, and did not produce conidia during extended incubation at the restrictive temperature. When shifted from the permissive to the restrictive temperature, swoH1 showed the temperature-sensitive swelling phenotype only after 8 h at the higher temperature. The swoH gene was mapped to chromosome II and cloned by complementation of the temperature-sensitive phenotype. The sequence showed that swoH encodes a homologue of nucleoside diphosphate kinases (NDKs) from other organisms. Deletion experiments showed that the swoH gene is essential. A hemagglutinin-SwoHp fusion complemented the mutant phenotype, and the purified fusion protein possessed phosphate transferase activity in thin-layer chromatography assays. Sequencing of the mutant allele showed a predicted V83F change. Structural modeling suggested that the swoH1 mutation would lead to perturbation of the NDK active site. Crude cell extracts from the swoH1 mutant grown at the permissive temperature had approximately 20% of the NDK activity seen in the wild type and did not show any decrease in activity when assayed at higher temperatures. Though the data are not conclusive, the lack of temperature-sensitive NDK activity in the swoH1 mutant raises the intriguing possibility that the SwoH NDK is required for growth at elevated temperatures rather than for polarity maintenance.

Quantitative Trait Loci Specifying the Response of Body Temperature to Dietary Restriction

Dietary restriction (DR) retards aging and mortality across a variety of taxa. In homeotherms, one of the hallmarks of DR is lower mean body temperature (T(b)), which might be directly responsible for some aspects of DR-mediated life extension. We conducted a quantitative trait locus (QTL) analysis of the response of T(b) to DR in mice using a panel of 22 LSXSS recombinant inbred strains, tested in two cohorts. T(b) in response to DR had a significant genetic component, explaining approximately 35% of the phenotypic variation. We mapped a statistically significant QTL to chromosome 9 and a provisional QTL to chromosome 17, which together accounted for about two thirds of the genetic variation. Such QTLs could be used to critically test whether the response of T(b) to DR also affects the response of life extension. In addition, this study demonstrates the feasibility of trying to map QTLs that affect other physiological responses to DR, including the life extension response. Importantly, the genes underlying such QTLs would be causal factors affecting these responses and could be identified by positional cloning.