Abstract: 【Objective】The aim of this study was 1) to analyze the role of PMRP (Putative Membrane Related Protein) in the progress of chloroplast development in Arabidopsis, 2) to illuminate the effect of PMRP on the photosynthetic capacity and cold resistance of Arabidopsis, 3) to provide a theoretical basis for improving the photosynthetic performance and enhancement of plant cold-resistance.【Method】PMRP RNAi and over expression vector were constructed and transformed into Agrobacterium tumefaciens EHA105, and then infected the buds of wildtype Arabidopsis(Columbia, Col-0), so we obtained the PMRP RNAi and overexpressing transgenic Arabidopsis plants; with wild type, PMRP RNAi and over-expressing transgenic Arabidopsis thaliana as materials, cell biology method was used to observe the chloroplast structure and starch grain accumulation; The CO₂ infrared analytical method was used to analyze the photosynthetic rate with different PMRP expression in Arabidopsis transgenic plants; Wild-type (Col-0), overexpression PMRP transgenic Arabidopsis and PMRP-RNAi transgenic Arabidopsis were grown at 21℃ with a 16-h-light/8-h-dark cycle. After 21 days, they were transferred to 4℃cold light incubator for 7 d and then cultivated for 1.5 h at 8℃, then were grown at 21℃ with a 16-h-light/8-h-dark cycle again for 7 d, then we analyzed the chilling resistance of PMRP transgenic Arabidopsis; Wild-type (Col-0), overexpression PMRP transgenic Arabidopsis and PMRP-RNAi transgenic Arabidopsis were grown for 14 days and there rosette leaves were used to determine the conductivity of cellular exudate.【Result】PMRP RNAi and overexpressing transgenic Arabidopsis plants were obtained. The photosynthetic rate of rosette leaves in wild-type (Col-0) was 7.3 μmol·m^-2·s^-1, but the photosynthetic rate in the 3 lines of PMRP-RNAi transgenic Arabidopsis plants was 8.8, 7.8 and 8.5 μmol·m^-2·s^-1 respectively, this results showed that the photosynthetic rate was increased with the decreased PMRP expression. Under cold stress condition, the green leaves rate of wild type (Col-0) was 48%, the green leaves rate of the 3 overexpression PMRP transgenic Arabidopsis lines was 48.6%, 47.8%, 49.2% respectively, the green leaves rate of the 3 PMRP-RNAi transgenic Arabidopsis lines was 65.9%, 67.4%, 68.3% respectively. These data indicate that the decreasing expression of PMRP enhanced the tolerance of Arabidopsis to cold stress. After 30 mins treatment in -8℃ condition, the cellular exudate conductivity of the rosette leaves in wild type Arabidopsis was 70.67 μS·cm^-1, the cellular exudate conductivity of the rosette leaves in the 3 lines of PMRP RNAi transgenic Arabidopsis plants was 48.57, 45.40 and 52.10 μS·cm^-1 respectively, this indicated that the decrease of PMRP expression decreased the damage of cell membrane significantly. We analyzed the ultrastructure of the fully expanded rosette leaf of wild-type and PMRP-RNAi transgenic Arabidopsis, imaging results showed that chloroplasts are ellipse in wild type (Col-0) and was approximately circular shape in PMRP-RNAi transgenic Arabidopsis. Under light condition, the starch grains accumulation obviously in both PMRP transgenic Arabidopsis and wild type; but in the dark environment, the accumulation of starch grains in chloroplasts of PMRP-RNAi transgenic Arabidopsis was more than that of wild type Arabidopsis.【Conclusion】The decreased expression of PMRP changes the chloroplast shape from ellipse to round, increased the starch grains significantly, and enhanced the cold resistance of Arabidopsis thaliana.

Key words: PMRP, cold resistance, starch grains, Arabidopsis