Biochemical responses and altered genetic expression patterns in ponderosapine (Pinus ponderosa Doug ex P. Laws) grown under elevated CO2

Biochemical and gene expression changes in response to elevated atmospheric CO2 were investigated in five maternal half-sibling breeding families of P onderosa pine. Seedlings were grown in a common garden located at Lawrence Livermore National Laboratory, in open-topped chambers (OTC) for two years. Chamber atmospheres were maintained at ambient, ambient + 175 mu L L-1, CO 2, or ambient + 350 mu L L-1CO2. Growth measurements showed significant inc reases in stem volumes and volume enhancement ratios in three of the five f amilies studied when grown under elevated CO2. Biochemical and gene express ion studies were undertaken to gain a mechanistic understanding of these ph enotypic responses. Biochemical studies focused on sucrose phosphate syntha se (SPS) specific activities at increase CO2 levels. Kinetic evaluations of SPS showed an increase in V-Max. Specific SPS probes revealed increases in the transcriptional levels of one SPS gene with exposure to increasing CO2 . RT-PCR differential gene displays showed that overall only a small fracti on of visualized gene transcripts responded to elevated CO2 (8-10%). There were also significant differences between the gene expression patterns of t he different families, some of which correlated with alterations in growth at elevated CO2 levels.