Preliminary Evaluation Of The Effects On Arabidopsis Thaliana Root Growth And Polar Auxin Transport Of Three Ent-kaurene Diterpenes

Isodon plants are important genus of the Labiatae family and are perennial herbs,shrubs, or sub-shrubs. The genus is composed of approximately150species that arewidely distributed in tropical and subtropical regions. Ent-kaurane diterpenoids arethe main natural constituent in this genus and are especially abundant in freshbranches and leaves. To date, over400ent-kaurane diterpenoids have been isolatedfrom these plants. Such abundant and varied secondary metabolites formed during thelong evolutionary process may have special meaning to the survival of speciesthemselves.The effects of Leukamenin E?Rabdosin B and Epinodosin on root growth ofArabidopsis thaliana seedlings were evaluated by using the methods of primary rootand lateral root vitality,GUS staining of DR5:: uidA marker, starch grain in root tip,addition of auxin and interruption of auxin transport. In addition, the correlationamong the root growth and initiation of lateral root with the levels of auxin inArabidopsis thaliana roots of Leukamenin E and Rabdosin B were studied in ourresearch. Finally, we determined the PIN family genes expression treated withLeukamenin E.The results are shown as follows:(1) Leukamenin E have no effect on primary root growth of Arabidopsis thalianaat concentration of10?M, while primary root is inhibited significantly with higherconcentration of Leukamenin E (20-80?M) and show a dose-dependent manner. Thelength and number of lateral root was promoted significantly at10?M, and thenumber of root primordium was promoted significantly at20?M, but its higher levelsat80?M, by contrast, had inhibitory effects. Additionally, all of the testedconcentrations (5-80?M) promoted Lateral root primordia density significantly ofArabidopsis thaliana. Histochemical GUS staining patterns of DR5::uidA indicated that DR5expressionat root tip was improved at lower concentrations of Leukamenin E (10?M,20?M)?and higher levels at40-80?M was no effect on it.(2) Primary root was promoted significantly at20?M, while inhibited significantlyat higher concentrations(80-120?M) of Rabdosin B. Additionally, the length andnumber of lateral root and Lateral root primordia density were all promotedsignificantly at tested concentrat-ions (40-120?M).Histochemical GUS staining patterns of DR5::uidA indicated that DR5expression at root tip was improved at concentrations of40-120?M of Rabdosin B.(3)Although Epinodosin inhibited primary root significantly at concentrations of40-120?M, the Lateral root primordia and length was promoted significantly.Thenumber of lateral root primordia was inhibited at concentrations of80-120?M.Histochemical GUS staining patterns of DR5::uidA indicated that DR5expressionat root tip was improved at concentrations of80and120?M of Epinodosin, othertreated had no effect.(4) The experiment of the interruption of auxin transport by NPA indicated that10?M Leukamenin E and80?M Rabdosin B could not recover the inhibitory effect oflateral root length by NPA, but in contrast, could significantly recover the number oflateral root primordium.Histochemical GUS staining patterns of DR5::uidA indicated that10?MLeukamenin E and80?M Rabdosin B could reduce DR5expression at cotyledoncompared with treatd use NPAalone, and improved expression at root tip.(5)80?M Leukamenin E,120?M Rabdosin B and120?M Epinodosin could affectThe root of geotropism of Arabidopsis thaliana.(6)The gens expression of PIN1?PIN2?PIN3?PIN4and PIN7was inhibited byLeukamenin E.(7)The influence mechanism of this three kinds of compound on polar auxintransport of Arabidopsis thaliana is quite another thing compered with NPA. The former lead to auxin accumulation in root tip by inhibiting the auxin output carriergene expression, but NPA is lead to auxin accumulation in cotyledon not influence onroot.In conclusion, the mechanism of Leukamenin E, Rabdosin B and Epinodosininhibit primary root and promote lateral root by the way of affecting polar auxintransport of Arabidopsis thaliana by inhibiting the auxin output carrier PIN familygens expression and lead to auxin accumulation in root tip.