Studies On Lipid Accumulation In Developing Seeds And Correlations Of Seed Oil Content With ACL, PEPc And PAL Activities In Brassica Napus

Brassica napus is one of the most important oilseed crops planted widely in the world and as a major source of edible vegetable oil and protein for human. Recently, high oil content has been researching target of rapeseed. This study mainly focused on the evolutions of material contents and three enzymes activites, and differences of material contents and three enzymes activities in developing seeds among different lines to attempt to find the factors influencing lipids accumulation.Canola lines with different oil content were selected for my experiment. After artificial pollination in full flowing, samples of developing siliques were collected at 18,25,32,39, 46 DAP(days after pollination) for physiological determinations covering physiological and biochemical parameters as follows:sucrose, glucose and fructose content; protein content; seed oil content; chlorophyll content in seed and silique wall; fatty acid content; activities of three enzymes involved in ACL, PEPc and PAL. We analyzed evolution of these parameters in developing seeds and the correlations between seed oil content with above factors. Results are as follows:1. In developing seeds, total sugar, glucose and fructose content were decreasing gradually; sucrose content changed in singlet (the peak value of sucrose content was in 25DAP); at 18 and 25 DAP, high oil content lines had the higher total sugar and sucrose content than other lines; in developing seeds, high oil content lines had the higher total sugar and sucrose content in average than other lines. At 18 DAP, there was extramarked positive correlation of seed oil content with sucrose content(r=0.9307**,n=6); at 25 and 46 DAP, there were also significantly positive correlation of seed oil content with sucrose content and the correlation coefficients were 0.8186* and 0.8492*, respectively. In developing seeds, there was significantly positive correlation of seed oil content with sugar content in average (r=0.8462*, n=6) and the extramarked positive correlation between seed oil content and sucrose content in average (r=0.9243**, n=6). Therefore, the experiments indicated that sucrose content was the key factor influencing seed oil content of different canola lines. Otherwise, sucrose content also influenced protein content in seeds. 2. In developing seeds, the photosynthesis system can produce NADPH and ATP for lipids accumulation, the chlorophyll content is an important parameter which meant the ability of photosynthesis; in developing seeds, high oil content lines (NJ7708 and NJ8953) had the higher chlorophyll content in average than other lines, whose content were 0.324mg·g-1FW and 0.323mg·g-1FW, respectively. Therefore, chlorophyll content is an important factor influencing seed oil content of 10 different canola lines.3. In developing seeds, no significant correlations of seed oil content with several fatty acids(palmitoleic acid, linoleic acid, linolenic acid and arachidonic acid) content were found; at 32 DAP, there were significantly negative correlations of seed oil content with palmitic acid and stearic acid content(r=-0.8254* and r=-0.8848*, n=6); there was extramarked positive correlation of oil content with oleic acid content in mature seeds(r=0.9456**,n=6); high oil content lines had the higher oleic acid content. Therefore, the experiment indicated that it maybe exist correlations between the compositions of fatty acids with seed oil content.4. There were significantly positive correlations of ATP-citrate lyase (ACL) activities during 32 and 39 DAP with oil content in mature seeds(r=0.6610* and r=0.7467*, n=10), indicating that ACL activities play very important role in lipids accumulation. There was also significantly positive correlation of peak value of ACL activities with oleic acid content in mature seeds(r=0.8360*, n=6), indicating that the compositions of fatty acid contents in rapeseed seeds probably be caused by high ACL activity.5. In developing seeds, no significant positive correlations of seed Phosphoenol-pyruvate carboxylase(PEPc) activities with oil content was found, indicating that seed PEPc activity does not play key role in lipids accumulation and seed PEPc was not the key enzyme in the lipids accumulation.6. In developing seeds, no significant negative correlations of seed Phenylalanine Ammonia-lyase(PAL) activities with seed oil content was found, the correlations of seed PAL activities with oil content was the highest at 32 DAP but not significantly at 0.05 level(r=-0.5505+, n=10, P<0.1), indicating that PAL activities play limited extent negative role in lipids accumulation.