Co-ordination of photosynthetic gene expression during low-temperature acclimation and development in Brassica napus cv. Jet Neuf leaves

Abstract

The effect of low-temperature acclimation and leaf age on the expression of two photosynthetic genes was examined in mature and young leaves of Brassica napus cv. Jet Neuf. Nuclear-encoded ( ssu) and chloroplast-encoded ( lsu) genes were used to examine the changes at the DNA, mRNA and protein level. After acclimation, expression of lsu and ssu genes was low in mature leaves and high in young leaves. Corresponding Western blots showed a similar pattern for polypeptide accumulation with lower amounts of SSU and LSU polypeptides in mature leaves and higher amounts in young leaves when compared to their non-acclimated counterparts. However, in acclimated mature leaves relatively more LSU and SSU polypeptides accumulated than did the corresponding transcript. Despite the disparities between protein and message levels during acclimation, protein turnover kinetics showed that LSU and SSU had similar stability in acclimated and non-acclimated leaves of both ages. From Western blots, the ratio of LSU:SSU showed that both polypeptides accumulated in proportion during cold acclimation. Methylation studies at various restriction sites of lsu revealed alteration at PstI and HindIII sites with acclimation.