Effects Of Polyamine Biosynthetic AtADC1 Gene On Root Growth In Arabidopsis Thaliana Seedlings

Polyamines,as a new plant hormone,involved in many processes of growth and development.but also affect greatly the growth of root.To analysis the effects of the key enzyme genes AtADCl of polyamine biosynthetic on root growth in Arabidopsis thaliana,we used Arabidopsis thaliana 350c mutant,at the same time Putrescine and D-arginine was used to study.We also used the maker line materials that correlat with the development of root.In the present study,we evaluated the AtADCl genes can not only effect the elongation growth of main root by influencing the cell division of main root apical meristematic zone,but also by influencing the distribution of auxin,thus affecting the root growth and development.The main results are as follows:1.Arabidopsis thaliana seedlings were treated with putrescine or D-Arg.The results showed that putrescine promoted the elongation of main root,while D-Arg inhibited significantly.Arabidopsis seedlings were treated with D-Arg of varying concentrations.The results showed that the degree of inhibition on main root growth was increased with an increase of D-Arg concentration(0.2 to 0.8 mmol/L).The observation of root tip structure by differential interference microscopy found that D-Arg decreased the cell number of main root meristematic zone and main root growth length in A.thaliana.2.We focused on the key enzyme genes AtADCl of polyamine biosynthesis by using AtADCl gene deletion mutant 350c in A.Thaliana.we observed that the main root length existed significant differences in the 8-day-old seedings.After that,we observed the main root tip of seedlings between 350c mutant and wild type and found that the number of cell in meristematic zone in 350c mutant root decreased,but there is no significant difference in the average length of cell in the elongation zone.the expression in the apex in 350c x CYCB1;1::GFP and 350c x CYCB1;1::GUS,compared with wild type CYCB1;1::GFP and CYCB1;1::GUS,were decreased.3.To analyse whether there is interaction relationship between AtADC1 gene and auxin,we performed the observation on hybrid materials,namely 350 c x DR5::GFP.The result showed that the fluorescence intensity in hypocotyledonary axis and root are significantly weaker than wild type DR5::GFP.Then we analysed the geotropism of root and the elongation of hypocotyledonary axis in the dark in the mutant 350c.The study found that there is no diference in geotropism and the length of hypocotyledonary between the mutant 350c and wild type.350cx DR5::GFP and DR5::GFP there were significant differences in fluorescence intensity and expression location,especially the fluorescence intensity of young leaf.We guess that the reduction of fluorescence in the root of 350 c x DR5::GFP significantly may be associated with less auxin content in young leaves.4.350 c x DR5::GFP seedlings were treated with IAA and grew in the dark.The results showed that mutant seedlings 350c differed from the wild type when them were in the response of auxin.IAA can enhanced the fluorescence intensity of leaf tip and petioles,reverting the expression of fluorescence in stoma,but reducing in the hypocotyledonary axis and hardly expressing in vein in 350 c x DR5::GFP seedings.The treatment with IAA and 6-BA,350c were slightly longer than the wild type.It suggested that main root of 350c mutant diminished in the response of IAA.