Research In Regulation Of Physiological Factors And Related Genes For Kernel Plumpness With The Peanut Mutant

The yield and quality of peanut (Arachis hypogaea L.) is denpended on its kernelsatiation index. Sucrose metabolism provides required energy to the growth of plant seeds,and supplies the organic compounds including starch, protein and fat with synthesis materials.Endogenous hormones also play important roles in plant growing development and yieldformation. Two peanut cultivars of normal seeds including Shanhua15with special big podand Baisha1016with small pod, and one wrinkled mutant line05D677and its donor line05D610were used as materials in this research. Dynamic changes of dry matter accumulation,nutrient content, endogenous hormones content, and activities of enzymes related to sucrosemetabolism were assayed during the development of pods and kernels. In addition, genesdifferential expression analysis between seeds of05D677and05D610was analysed. Themain results were as follows:1. Comparison of dry matter accumulation between mutant and normal varieties in developingpods or kernelsThe24-60days after peg penetration(DAP) was the rapid dry weight accumulation phase,during which the average of both pod dry matter accumulation rate (PKW) and thecorresponding kernel dry matter accumulation rate (KKW) of05D677were significantlyinferior than that of Shanhua15,05D610and Baisha1016. The differences among fourvarieties during the effective filling stages were not significantly.2. Comparison of nutrient content between mutant and normal varieties in developing kernelsThe four varieties shared much the same dynamic changes trends of fat and protein in theyoung pods or kernels. However, fat content of05D677was highly significantly lower thanthat of other three varieties (lines), while protein content of05D677was higher than that of05D610. Soluble sugar content of05D677was highly significantly higher than that of otherthree varieties at36DAP. Hexose/Sucrose ratio of05D677was highly significantly lowerthan that of three normal varieties (lines) in the early pod developing period.3. Comparison of endogenous hormones content between mutant and normal varieties indeveloping kernelsThe four varieties shared much the same dynamic changes trends of cytokinin(Z+ZR),gibberellin(GA), auxin(IAA) and abscisic acid(ABA) in the young pods or kernels. However,GA content of05D677peaked six days later than other three varieties (lines). The peak value of Z+ZR, GA and ABA content of05D677were all highly significantly lower than that ofother three, while the opposite result was discovered as to IAA content.4. Correlation analysis between hormones content and dry matter accumulation rate of podsand kernelsIn the middle and later periods of pod expansion, Z+ZR, GA and ABA content were inhighly significant positive correlation withPKWandKKW, while the opposite for IAA content.Z+ZR content were in highly significant positive correlation withPKWandKKWin the earlypod filling period, and the same result was found between GA content andPKWin the laterfilling and mature period. ABA content was in highly significant negative correlation withPKWandKKWin the later pod filling, while the opposite withPKWin the mature period.5. Comparison of activities of enzymes related to sucrose metabolism between mutant andnormal varieties in developing pods or kernelsActivities of both soluble acid invertase and neutral invertase were higher than that ofsucrose synthase toward cracking direction of4varieties (lines), and soluble invertases werekey enzymes within sucrose decomposition. Synthesis activities of sucrose synthase werehigher than sucrose phosphate synthetase, and sucrose synthase were key enzymes withinsucrose synthesis. Acid invertase functioned mainly at12-42and54-72DAP, and neutralinvertase functioned mainly at42-60DAP. Activities of enzymes related to sucrosemetabolism of05D677were higher than that of other three varieties (lines), but thedifferences were not significant.6. Genes differential expression analysis between seeds of05D677and05D610Compared with gene expression profile of kernels of05D610at24DAP,540genes werefound different of05D677,67.41%of which were down-regulated. There are25up-regulatedgenes and129down-regulated genes which log2Ratio were greater than two. Gene encodingthe hormone synthesis key enzyme of1-deoxy-D-xylulose-5-phosphate synthase and sucrosetransport protein were both found down-regulated.The main conclusion of our study was that declinedKKWof05D677was the mostimportant reason for shriveled seeds. Insufficient of synthetic substrates IPP caused bydown-regulated DXP gene was possibly the reason for synthesis blocking of GA, CTK andABA. Down-regulated sucrose transport protein gene was possibly one of the reasons fordeclined Hexose/Sucrose ratio of05D677.