Role of glycerophosphodiester phosphodiesterase in rice leaf blades in elevated CO 2 environments.

Glycerophosphodiester phosphodiesterase (GDPD; EC 3.1.4.46) is involved in plant phosphate (Pi) utilization and its expression is upregulated under phosphorus (P)-deficient conditions. Although rice was grown under P-sufficient conditions, the transcript levels of specific OsGDPD were upregulated in mature rice leaf blades (LB) in elevated CO 2 (eCO 2 ) environments. Expression and subcellular localization of GDPD, and contents of Pi, sugar phosphates and carbohydrates were analysed to clarify the physiological function of GDPD in rice under eCO 2 . Under eCO 2 , expression of specific OsGDPD increased only in mature rice LB in which low Pi concentrations were observed. Moreover, eCO 2 -induced OsGDPD2 and OsGDPD3 were localized in the plastid, indicating that GDPD2 and GDPD3 may be related to plastidic functions, such as carbon assimilation. Although rice LB contained more carbohydrates under eCO 2 than under ambient CO 2 , the phosphoglucose content decreased under eCO 2 , suggesting that the need for excess phosphoglucose to synthesize carbohydrates under eCO 2 causes a local Pi deficiency. Furthermore, we confirmed that glycerol-3-phosphate produced by the catalysis of GDPD from glycerophosphodiester contributes to carbohydrate accumulation in rice LB. Our findings suggest that local Pi deficiency due to excess carbohydrate accumulation under eCO 2 influences GDPD to enhance glycerophosphodiester hydrolysis.