The Mechanisms Of Stomatal Movement And Root Development Regulated By Sinapate Ester Metabolism In Arabidopsis Thaliana

Phenylpropanoid metabolic pathway is an important pathway of plant secondary metabolism.Sinapic acid and its derivatives are important intermediate products of phenylpropanoid metabolic,and play important roles on seed germination,plant growth and development,defense,and so on.Sinapic acid is the synthesized precursor of sinapic acid esters including sinapoylglucose,sinapine and sinapoylmalate.The sinapoylglucose is converted to sinapoylmalate by sinapoylglucose:L-malate sinapoyltransferase(SMT).And it has been reported that under the ultraviolet rays(UV)treatment,the content of sinapoylmalate in Arabidopsis leaves increased,indicating that sinapoylmalate played an important role in the response of Ultraviolet-B(UV-B)in Arabidopsis leaves.But the mechanism of sinapoylmalate involved in regulating of stomatal movement induced by UV-B is still not clear.We treatd Arabidopsis wild type(WT)and sinapic acid ester synthesis mutants sngl,brtl with 0.5 W m-2 UV-B for two hours,and detected the content of malate by High-performance Liquid Chromatography-electrospray Ionization Mass Spectrometry(LC-MS).We also detected the accumulation of reactive oxygen species in the leaves by Diaminobezidin(DAB)and the accumulation of reactive oxygen species in the guard cells by 2',7'-dichloroflurescin diacetate(H2DCFDA).The results showed that after exposed to UV-B,the accumulation of malate in the leave low epidermis of sngl was exactly lower than that of WT;and reactive oxygen species increased in WT,sng1,and brt1.But,the reactive oxygen species in sng1 were exactly higher than that of WT.These results suggested that the lack of the SMT synthesis in sng1 lead to the reduce of malate synthesis,and increased the outflow of malate in stomatal,and changed the intracellular turgor pressure,then further influenced the accumulation of H2O2.It may induce the related signaling pathways that lead to stomatal closure in order to reduce ultraviolet radiation damage to the plants.Sinapic acidester metabolic pathways not only involve in regulating the stomatal movement induced by UV-B,but also play an important role in the development of the roots.The roots of the plant have the ability to guide their growth at a specified angle from the gravitropism to ensure that the shoot is positioned to maximize it's light-harvesting capabilities and the roots are positioned downward so as to maximize the uptake of water and nutrients.We treated the seeds of Arabidopsis with exogenous sinapic acid and found the development.of the roots had been affected obviously,it suggested that sinapoylglucose participates in regulating the development of the root,but the mechanism is still unclear.We treated Arabidopsis seeds with different concentration of sinapic acid,and found when the concentration of sinapic acid was 0.5 mM,the gravitropism of the roots were affected obviously,and the inhibition the of the main roots growth,promoted the growth of the lateral roots.We tested the sinapoylglucose content in the roots by High Performance Liquid Chromatography(HPLC),it showed that the content of sinapoylglucose improved significantly both in the WT,sng1 and brt1.Besides,the increase of the sinapoylglucose in the brt1 was obviously lower than that of WT and sng1.We speculated that the reason may be that brt1 is UDP-glucose:sinapate glucosyltransferase(SGT)mutant.Our results imply that sinapic acidester metabolism may regulate the development of the root by influencing the glucose metabolism.