CO2 enrichment modulates both proteinase and proteinase inhibtors in maize

Proteolytic enzymes are essential for protein turnover and hence the ability of cells to respond to changing environmental conditions. Since one of the focuses of this study was to identify changes in the expression and activity of proteases and their inhibitors in response to development or CO2 enrichment, the following studies were performed. Expression of protease inhibitor and protease-related transcripts were studied, and protease activities were investigated using biochemical techniques. Shoots contain high activities of both serine and cysteine proteases. Leaf protease activities were greatly increased by growth with CO2 enrichment. Transcriptome analysis was performed on young and old source leaves of maize plants that had been grown for 8 weeks under either 350μl l-1 (low) or 700μl l-1 (high) CO2. However, relatively few protease transcripts were modified by CO2 in young and old source leaves. Growth at high CO2 favours decreased source leaf cysteine proteases and increased cystatins.