An increase in unsaturation of fatty acids in phosphatidylglycerol from leaves improves the rates of photosynthesis and growth at low temperatures in transgenic rice seedlings

The level of cis-unsaturated fatty acids in phosphatidylglycerol (PG) from rice leaves was genetically altered from 19.3% in the wild-type to 29.4 and 32.0% in T1 plants segregated with cDNAs for glycerol-3-phosphate acyltransferase of chloroplasts (GPAT; EC 2.3.1.15) from Arabidopsis (+AGPAT plant) and spinach (+SGPAT plant), respectively; and to 21.4% in a non-transformant segregated from +SGPAT plants (-SGPAT plant). In all these plants, O₂ evolution from leaves was similar at 25°C and was impaired to a similar extent at 5 and 11°C. However, in parallel with the levels of cis-unsaturated fatty acids in PG, +AGPAT and +SGPAT plants showed less impaired rates of O₂ evolution from leaves than the wild-type and -SGPAT plants at 14 and 17°C. In agreement with this, the fresh weight of 14-day-old seedlings increased to 571±18, 591±23, 687±32 and 705±31 mg in the wild-type, -SGPAT, +AGPAT and +SGPAT plants, respectively, after 6 weeks at 17/14°C (day/night). These results demonstrate the practical importance of the present technology with GPAT in improvement of the chilling sensitivity of crops.