Regulation of carbon metabolism in two maize sister lines contrasted for chilling tolerance.

Maize can grow in cool temperate climates but is often exposed to spring chilling temperatures that can affect early seedling growth. Here, we used two sister double-haploid lines displaying a contrasted tolerance to chilling to identify major determinants of long-term chilling tolerance. The chilling-sensitive (CS) and the chilling-tolerant (CT) lines were grown at 14°C day/10°C night for 60 days. CS displayed a strong reduction in growth and aerial biomass compared to CT. Photosynthesis efficiency was affected with an increase in energy dissipation in both lines. Chilling tolerance in CT was associated with higher chlorophyll content, glucose-6-phosphate dehydrogenase activity and sucrose-to-starch ratio. Few changes in cell wall composition were observed in both genotypes. There was no obvious correlation between nucleotide sugar content and cell wall polysaccharide composition. Our findings suggest that the central starch-sucrose metabolism is one major determinant of the response to low temperature, and its modulation accounts for the ability of chilling-tolerant plants to cope with low temperature. This modulation seemed to be linked to a strong alteration in the biosynthesis of nucleotide sugars which at a high level, could reflect the remobilization of carbon in response to chilling