Somatic Embryogenesis Induction and the Difference of Callus of Eucalyptus urophylla×Eucalyptus grandis

In this study,the somatic embryogenesis induction and shoot regeneration were studied systematically in elite clone of Eucalyptus urophylla×E.grandis by comparing the variety of combinations of different growth regulators.Embryogenic callus and non-embryonic callus of E.urophylla×E.grandis were used as explants to study the changes of different kinds of callus,and the mechanism of embryogenic callus of E.urophylla×E.grandis was revealed through analyzing histocytological changes,detecting physiological,biochemical indices and fluorescence quantitative PCR.This work laid the foundations for plant regeneration of E.urophylla×E.grandis through somatic embryogenesis.(1)Somatic embryogenesis was observed in callus in the presence of MS+0.1mg/L NAA+0.01mg/L TDZ.The best somatic embryogenesis rate(16.7%)was obtained when explants treated with 0.5mol/L sucrose for 12 h.The embryogenic cells were consisted of small,tight arrangement and has the phenotype of embryogenic cell.Non-embryogenic cells were large loosely arranged and usually irregular.(2)Histological analysis of incubated explantsrevealed that embryogenic cells exhibited common features characteristic.(3)Proteins and activities of antioxidant enzymes were evaluated in embryogenic and non-embryogenic calli in E.urophylla×E.grandis.For embryogenic calli,PPO,CAT,SOD activities and protein content showed the significantly higher level than those of non-embryogenic calli.For non-embryogenic calli,lignin and soluble sugar contents,POD and PAL activities showed the significantly higher level than those of embryogenic calli.There was a significant difference of the levels of gene mRNA expression among trans-cinnamate 4-monooxygenase,starch phosphorylase,glutathione S-transferase,glucose-1-phosphate adenylyltransferase,glucose-6-phosphate isomerase,chorismate synthase,PAL.The difference between embryogenic callus and non-embryonic callus of E.urophylla×E.grandis was revealed.