Epinodosin Promotes The Growth Of Arabidopsis Thaliana Root By Regulating The Polar Auxin Transport

Ent-kaurane diterpenoid compounds widely exist in the Labiatae Isodon plants.These secondary metabolites are released to the soil by litters,and they affect the growth and development of themselves and the surrounding plants.Such affections have an important impact on the ecological environment,namely,allelopathy.Auxin is synthesized in certain parts of plants,including leaves,roots,leaf primordia and seeds,etc.Through a variety kinds of polar transport proteins,auxin is transported to certain tissues of plants and formed the gradient distributions,which will ultimately affect the growth and development of plants.The research confirmed that allelochemicals can affect the growth and development of targeted plants by regulating the auxin pathways in them,but few researches reported that terpenoids shall promote the of growth and development of targeted plants by mediating the polar transport of auxin.In this paper,Ent-kaurane diterpenoid compound epinodosin was chosen as the tested compound,the Arabidopsis thaliana ecotype Col-0,PINs::PINs-GFP and AUX1:: AUX1-YFP fusion protein marker plant,PINs:: GUS and AUX1:: GUS transgenic reporter plant were used as the experimental materials.Then,how the epinodosin promote the growth and development of roots in Arabidopsis thaliana was evaluated,and the influence that such compounds had on the cell division of the root meristematic zone was characterized at a cellular level.Also,this paper focuses on the correlations between the influences that epinodosin had on the auxin polar transportations of Arabidopsis thaliana and certain promotions of the growth of Arabidopsis thaliana.This paper provides new evidence and ideas towards how the secondary metabolites promote the growth of plants under low concentration.(1)10?M?20?M?30?M and 40?M epinodosin show significant growth promoting effects toward the primary roots and lateral roots after they were used in Arabidopsis thaliana seedlings for 96 hours.20?M and 40?M epinodosin,respectively,show the most obvious influences on the Arabidopsis thaliana's lateral roots and primary roots;the same concentration of epinodosin can significantly promote the growth of the dark cultivated Arabidopsis thaliana's petiole,but they had no significant influence on the growth of hypocotyl.(2)10?M?20?M?30?M and 40?M epinodosin induce the growing population of meristem cortex cell in Arabidopsis thaliana,which can show the promoting effects that epinodosin had on the root tip cell division in Arabidopsis thaliana.(3)10?M?20?M?30?M and 40?M epinodosin,within 24 hours,induce the DR5::GFP fusion protein markers,which results in the significantly enhanced fluorescence of the small column root tip cell and the quiescent center cell compared with the control group.After 96 hours,the fluorescence of the small column root tip cell and the quiescent center cell decreased,but its fluorescence of the lateral root crown on either side of the cells was enhanced,and such fluorescence has concentration dependence.These results suggest that epinodosin made auxin accumulate in the column small cells,the quiescent center and the surrounding lateral root crown intracellular in a short period of time,but with the increase of incubation time,auxin concentrations in these cells were decreasing.(4)After 10?M?20?M?30?M and 40?M epinodosin processing Arabidopsis thaliana seedlings for 24 hours ~ 96 hours,the output carrier PIN1 and auxin PIN2 expressed in transcription level and protein levels were significantly abating,and PIN4 also had weakened phenomenon under the condition of high concentration in transcription level and protein expression levels;Auxin input carrier AUX1 was significantly enhanced in transcription level and protein expression levels,and the output carrier---PIN3 shows the enhancement in transcription level and protein expression level after 96 hours;no significant change was found in output carrier protein PIN7.(5)After 10?M?20?M?30?M and 40?M epinodosin processing five kinds of carrier deficient mutants and wild type Arabidopsis thaliana seedlings for seven days,it appears that epinodosin has the same effects on pin4-3 mutant as it has on wild types.That is,epinodosin has promoting effects on the growth of taproots and the formation of lateral-root primordia,where such effects show significant or greatly significant differences.While epinodosin does not has any significant promoting effects on the growth of taproots and the formation of lateral-root primordia of the pin1?pin2 salk?aux1 salk mutants.Also,the promoting effects that epinodosin has on the taproots and lateral-roots of pin3-4 are weakened compared to it has on the wild types.Such results show that epinodosin can promote the growth of taproots and lateral-roots of Arabidopsis thaliana seedlings through pin1?pin2?pin3?aux1.In conclusion,under the 10?M ~ 40?M concentration,the Ent-kaurane diterpenoid compound epinodosin adjust the auxin concentration inside the cell of the Arabidopsis thaliana root column cells,the quiescent center and the surrounding lateral root crown and promote the root cell division,its growth and development and lateral root primordium development by adjusting the seedling root auxin output carrier PIN1,PIN2,PIN3 and PIN4 and the activity of the auxin input carrier AUX1.