Function Of Microtubules In Root Of Arabidopsis Response Osmotic Stress

Osmotic stress caused by soil drought and salinization is the common factoraffecting grown of plant and resulting in reduction in crop yield worldwide. Therefore,to make a study of osmotic stress mechanism is of far reaching importance to revealplant growth regulation theory and to agricultural production.Plant cytoskeleton microtubule may affect cell division and determine cell polarity.So, it plays an important role in plant’ growth and morphogenesis. Change ofenvironment osmosis may result in depolymerization and rearrangement of cellmicrotubule. In that way, is microtubule arrangement mode related to plant response toosmotic stress? Taking Arabidopsis as the subject, this article would discuss the role thearrangement mode of cell microtubule cytoskeleton played in Arabidopsis roots’response to osmotic stress the theory and method of plant physiology and biophysics.In the present research, we compared the roots of growth situation betweenGFP-MBD transgenic Arabidopsis and wild-type Arabidopsis in different culture modes,as well as the imagings of microtubules in different microtomies. These results provedthat GFP-MBD labeled gene transformed into Arabidopsis had no effect on theelongation and growth of Arabidopsis root. Moreover, GFP-MBD transgenicArabidopsis and wild-type Arabidopsis response to the osmotic changes is consistent.With GFP-MBD transgenic Arabidopsis as research material, a research system underfluid culture mode featured by culture fluid microtomy and observation of cellmicrotubule under confocal microscope was established.In this research, four osmotic gradients such as1/2MS,1/2MS+50mM mannitol,1/2MS+100mM mannitol and1/2MS+200mM mannitol were selected to make study onthe effect of osmotic stress upon the growth of arabidopsis roots. After seven days ofcultivation, the average length of Arabidopsis root in1/2MS,1/2MS+50mM mannitol,1/2MS+100mM mannittol and1/2MS+200mM mannitol is respectively27.865mm,21.876mm,17.532mm and13.972mm and the average length of cells in maturationzone is respectively390.658μm,315.386μm,57.188μm and131.893μm. It was foundthat the osmotic stress of1/2MS+50mM mannitol could significantly restrain thegrowth of Arabidopsis roots and the length of root tip cell in maturation zone.Furthermore, the restraint increasingly intensified with the increasing amount ofpenetrant. Microtubule depolymerizing agent oryzalin was used to dispose arabidopsis. It wasfound that, after microtubule depolymerization, the average length of Arabidopsis rootsin1/2MS,1/2MS+50mM mannitol,1/2MS+100mM mannitol and1/2MS+200mMmannitol is respectively22.575mm,17.315mm,14.146mm and10.926mm, and afteroryzalin disposal, growth of root in nutrient mediums with various osmotic gradientproved slower than that in comparison. Therefore, it reasonable to think thatmicrotubule has participated in plant roots’ response to osmotic stress. Furtherobservation of the arrangement of Arabidopsis root’ cell microtubule in each osmoticgradient shown that the length of Arabidopsis root cells in1/2MS+50mM mannitolranged from80μm to260μm, the included angle between arrangement direction ofmicrotubule and longitudinal axis of the root is greater than that in1/2MS ulturemedium. The root cells of Arabidopsis in1/2MS+100mM mannitol have an lengthranging from80μm to250μm and the included angle between arrangement direction ofmicrotubule and longitudinal axis of the root is greater than that in1/2MS culturemedium. All these shown that under osmotic stress, plant could regulate the length of itsroot cells through changing the arrangement mode of its microtubule, and accordingly,regulate the growth of its roots.TCH gene may affect the arrangement of cell microtubule, in that way, whetherTCH gene has participated in plant’ response to osmotic stress regulation or not, throughcomparing difference of Arabidopsis mutants tch1~3between mutants roots and wildtype Arabidopsis roots under osmotic stress, it was found that growth of tch1~3in fluidnutrient medium all exceed that of wild type, furthermore, there are differences betweendifferent tch mutants, which shown that TCH gene may participate in plant’ response toosmotic stress.