The Role Of Heterotrimeric G Protein In Auxin Induction, Growth And Development Of Arabidopsis Thaliana Roots

Wild type (ws)Arabidopsis thaliana , null mutants of G proteinαsubunit gene (gpα1^-1 and gpα1-2) and over-expressed mutants (wGαand cGα) were investigated as material, The effect of different auxin on the growth of Arabidopsis thaliana roots were researched and the role of heterotrimeric G protein in auxin induction, growth and development of Arabidopsis thaliana roots and G protein effector were studied, served as theoretical standard of auxin regulating mechanism in root growth and development .The main results were as follows:1.Wild type (ws) Arabidopsis thaliana were treated respectively with NAA, 2,4-D, IAA, IBA at different concentrations (0-0.2 mg·L^-1) to comparatively examine some morphological parameters in growth and development of the roots. It was showed that increasing concentrations of auxin inhibited elongation of the taproots in a dose-dependent way,while the growth and development of the lateral roots were promoted.The taproots were highly inhibited,while the lateral roots were little promoted even at 0.01mg·L^-1 2,4-D induction.The lateral roots number were the most at 0.01mg·L^-1 NAA.2.Wild type (ws) Arabidopsis thaliana, two null mutants of G proteinαsubunit gene (gpα1^-1 and gpα1-2) and two over-expressed mutants of G proteinαsubunit gene (wGαand cGα) were treated with NAA, 2,4-D, IAA, IBA at different concentrations to comparatively examine some morphological parameters relative to growth and development of the roots. It was demonstrated that theαsubunit of G protein has no effect on the growth of taproot which induced by four kind of auxin, while it played a positive regulation role in the growth of lateral roots induced by NAA but a negative regulation role in the growth of lateral roots induced by 2,4-D and IAA respectively, while there had no effect on both taproots and lateral roots in IBA induction.3.It was proved that G protein participate in the regulation of lateral roots growth and development in NAA and 2,4-D induction, there must be effector of G protein,which may be Ca²⁺ channel. Then based on the investigation above,voltage dependent calcium channel blockers, including organic blockers such as Verapamil and Diltiazem(100μmol·L^-1)and inorganic blockers such as Lanthanum Chloride and Polyaluminum Chloride(10μmol·L^-1, 50μmol·L^-1,100μmol·L^-1)were added to observe the effect of calcium channel blockers on growth of Arabidopsis thaliana roots.the result showed that extracellular Ca²⁺ had intense relation to root growth and development in NAA induction. Ca²⁺ channel organic blockers had no effect on root growth and development, while inorganic blockers had.The result demonstrated that extracellular Ca²⁺ influx into cell by voltage dependent calcium channel in course of root growth and development induced by NAA and G-protein effector was calcium channel, while extracellular Ca²⁺ did not participate in growth and development of Arabidopsis thaliana root induced by 2,4-D .