Variations of the peach fruit transcriptome during ripening and in response to hormone treatments

Peach has fleshy climacteric fruits. Their ripening is controlled by both endogenous and exogenous signals to link the genetic determinants with the environmental conditions. Genomic tools, such as microarray RNA profiling, offer new prospects to study in a holistic way complex biological problems such as fruit ripening. We have adopted a microarray approach to monitor transcriptome changes in peach fruits during their transition from a pre-climacteric to a climacteric stage. Furthermore, the variations of gene transcription mediated by applications of exogenous ethylene and auxin to pre-climacteric fruits have also been analysed. In peach fruits the ripening process needs vast transcriptional changes to occur, and the hormone ethylene controls many of these changes. Among the many variations occurring during ripening, we observed that some genes coding for various isoforms of the glycolytic enzymes were up-regulated. Several hypotheses are presented to account for these results

Influence of exogenous sucrose on the greening of oat

The greening of roots and leaves has been studied in whole oat seedlings grown on White's medium either with or without 2% sucrose. The added nutrient promotes chlorophyll synthesis and chloroplast differentiation in the roots. Yet it manifests a negative effect in the foliar tissues where it accelerates the decline in chlorophyll as well as the chloroplast ultrastructural alterations usually associated with senescence. The negative effect of the nutrient in the leaves is probably a consequence of the addition of exogenous sucrose to the endogenous sugars produced by photosynthesis. The foliar tissues would therefore be in the presence of high sucrose concentrations, which are known to be harmful for the photosynthetic apparatus. SDS-PAGE analysis of thylakoid polypeptides from root and leaf chloroplasts has revealed organ-specific differences in the electrophoretic patterns