| Chloroplast is an organelle with double envelope in plant cells. As an important organelle for plant photosynthesis and energy conversion, chloroplast is the focus of research bacause of its vital physiological significance. Stress physiology research in recent years is also very hot. The aim of revealing stress-resistant mechanism in plants and animals is to make them better adapt to the changing environment. However, the reseach about the relationships between the chloroplast devision and stress are rarely reported. In this study, by using Arabidopsis WS, Col-0 wild type and chloroplast devision mutant arc6, ftsZ1-1, ftsZ2-1, ftsZ2-2, we investigated whether the changes of chloroplast shape, volume and number affect plant stress resistance. The result are as follows:First, we checked a series of physiological inexes after heat shock treatment, including survival rate, fresh weight, chlorophyll content, soluble protein content, ATP content, H2O2 content, and semi-quantitative of heat shock genes. From these results, we speculated that the thermo-tolerance of arc6, ftsZ1-1, ftsZ2-1, ftsZ2-2 mutants were lower than that of the wild type, and the thermo-tolerance become weaker by the severer of chloroplast devision defects. So the thermo-resistence ability is arc6<ftsZ1-1<ftsZ2-1<ftsZ2-2. These results indicated that chloroplast devision affect plant resistence to heat shock, and chloroplasts may play a crucial role in thermo-tolerance.Then we investigated the germination rate and survival rate of these mutants under salt stress. The results showed that arc6 mutant was more sensitive to salt than WS. And by the increase of the NaCl concentration, germination rate of arc6 decreased greater. However, ftsZ1-1, ftsZ2-1 and ftsZ2-2 exhibited a strong salt tolerance in germination rate. When the germination rate of Col-0 decreased to 20% or less,90% seeds of ftsZ1-1, ftsZ2-1 and ftsZ2-2 germinated. About the survival rate, the wild type showed more tolerance than all the four mutants to salt stress. The survival rate under salt stress among the four mutants is arc6 <ftsZ1-1<ftsZ2-1<ftsZ2-2, indicating that chloroplast play a role in salt resistence.To investigate whether chloroplast devision mutants have defects in drought stress, we added mannitol in the culture medium to mimic drought condition. The results showed that the germination rate of arc6 mutant were always lower than wild-type in the same manitol concentration; However, ftsZ1-1, ftsZ2-1 and ftsZ2-2 exhibited a strong drought tolerance in seeds germination. The survival rate of arc6 mutant was always lower than WS in the same manitol concentration, indicating that drought stress still had greater impact on growth of arc6; whereas ftsZ1-1, ftsZ2-1 and ftsZ2-2 and Col-0 had the similar survival rate under the same manitol concentration.We also checked the germination and survival rates of the mutants in the medium containing phytohormone ABA. The germination rate of arc6 mutant was lower than WS in all the concentrations of ABA; However, ftsZl-1, ftsZ2-1 and ftsZ2-2 had higher germination rate than that of the Col-0 in the same manitol concentration. Survival rate of arc6 was lower than that of WS in all the ABA concentraion, whereas Col-0 and ftsZl-1, ftsZ2-1 and ftsZ2-2 have similar survival rates in all the ABA concentration, and no significant difference was found.To sum up, chloroplasts played an important role in plants thermotolerance, but we can not get consistant conclusion whether chlorplasts have a positive or negative function in resistence to other stresses. |
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