Gene expression profiling of rice grown in free air CO2 enrichment (FACE) and elevated soil temperature

Rising atmospheric CO2 concentration is accompanied by global warming. However, interactive effects of elevated CO2 and soil temperature have not been well studied in plants. Here, we studied the effects of free air CO2 enrichment (FACE, ambient +20 Pa), elevated soil temperature (+2 °C), or a combination of both on gene expression in developing 10th and fully expanded flag leaves of rice by microarray. Gene expression was significantly affected by FACE and 400–600 up-regulated or down-regulated genes were identified in each experimental condition. Overall, elevated soil temperature was likely to increase the number of differently expressed genes. Among them, only 31 up-regulated and 83 down-regulated genes were common irrespective of the leaf stage and soil temperature. These included up-regulation of sucrose transporter and fructosyltransferase and down-regulation of chlorophyll a/b binding protein, nitrate transporter and aquaporin, though most of differently expressed genes were functionally unknown. Although there were some exceptions, the expression of most of primary metabolism genes was not significantly altered by FACE. The expression of genes related to CO2 fixation such as Rubisco and carbonic anhydrase were down-regulated, whereas a large proportion of genes related to sucrose synthesis, glycolysis, TCA cycle and N fixation were up-regulated under FACE, though changes were small in all cases. These results might reflect the transcriptional adaptation of metabolism to FACE, reducing the CO2 fixation capacity and stimulating the dark respiration.

Research highlights▶ Gene expressions analyzed by microarray were significantly affected by FACE. ▶ Elevated soil temperature increases the number of differently expressed genes. ▶ The expressions of CO2 fixation genes such as Rubisco were down-regulated. ▶ Many sucrose synthesis, glycolysis, TCA cycle and N fixation genes were up-regulated.