Study Of Interactions Between Strigolactones And Other Signaling Moleculars In Mycorrhizal Sesbania Cannabina

Salt stress can cause crop physiological drought and hinder the normal growth and development,make them damage or death eventually.The arbuscular mycorrhizal symbiosis can alleviate salt stress by altering strigolactone levels in Sesbania cannabina.To investigate the intimate mechanisms associated with the S.cannabina-AM fungus interaction,a simple and highly sensitive method was first developed for the detection of strigolactone extracted from roots of S.cannabina by germination bioassay.Then strigolactone was identified by high performance liquid chromatography connected to tandem mass spectrometry(LC-MS-MS).Further more,we studied the salt stress tolerance under different strigolactone levels after different treatment of NaCl in AM S.cannabina seedlings.The relationship between SLs,ABA and H2O2 and their roles in response to salt stress were also studied in AM S.cannabina seedlings.The aim of this study was to investigate the mechanism by which strigolactones enhance salt stress tolerance in arbuscular mycorrhizal Sesbania cannabina seedlings.1.The results were showed that the extracts from roots of S.cannabina could stimulate O.cumana and P.ramose seed germination effectively,germination rates were 54%and 66%,respectively.It was suggested that these two seeds could be used to detect strigolactone levels in S.cannabina.Using LC-MS-MS,we obtained the data of parent ion(m/z=317,m/z=383 and m/z=357)and daughter ion(m/z 97)for the compound in the sample.Further more,the relative abundance results of m/z=317,m/z=383 and m/z=357 suggested that strigolactone levels could be elevated by phosphorus starvation,accordingly,the compound(m/z=317,m/z=383 and m/z=357)was preliminarily identified as natural strigolactones in S.cannabina..2.Strigolactone levels,as determined by means of germination bioassay,gradually increased with treatment time of NaCl applied.Inhibition of NADPH oxidase activity and chemical scavenging of H2O2 significantly reduced strigolactone-induced salt tolerance and decreased strigolactone levels.The H2O2-induced strigolactone accumulation was accompanied by increased tolerance to salt stress.These results strongly indicated that elevated H2O2 concentration resulting from enhanced NADPH oxidase activity regulated strigolactone-induced salt stress tolerance in arbuscular mycorrhizal S.cannabina seedlings.3.Strigolactone and abisic acid levels have the same trend under different treatment time of NaCl applied.The relationship between SLs,ABA and H2O2 and their roles in response to salt stress were studied in AM S.cannabina seedlings.The results showed that SLs content was elevated after treatment with ABA and reduced with the inhibition of ABA biosynthesis.ABA-induced SLs production was blocked by pre-treatment with dimethylthiourea(DMTU),an H2O2 scavenger.On the other hand,ABA production was not sensitive to DMTU.ABA could only induced partial and transient increases in salt stress tolerance of the TIS108 treatment plants,whereas SLs induced strong and prolonged increases in the tungstate treatment plants.These results strongly suggest that ABA plays an important role in H2O2-dependent induction of salt stress tolerance by SLs in AM Sesbania cannabina seedlings.