Study On Salt Tolerance Of MYB Transcription Factor Of Casuarina Equisetifolia

The MYB(v-myb avian myeloblastosis viral)transcription factor family is one of the most important transcription factors in plants,which can regulate plant growth and is related to the metabolism of anthocyanin,lignin,phenylpropanoid and other products.In addition,the MYB transcription factor family also plays an important role in plant signal transduction,secondary metabolism regulation,and stress(such as salt stress).Plant MYB transcription factors are divided into four categories according to the number of R-repeat,and R2R3-MYB transcription factors mainly play a role in stress.Casuarina equisetifolia is an ideal tree species for greening coastal saline-alkali land because of its outstanding resistance to typhoons,deserts,droughts and salinity.At present,there are few reports on the molecular mechanism of MYB transcription factor involved in the response of casuarina to salt stress.The results obtained are as follows:1.Based on the Casuarina genome database,the MYB transcription factor family in Casuarina was analyzed and compared with the MYB amino acid sequences of Arabidopsis thaliana.The phylogenetic tree was constructed,and a total of 25 subfamilies were obtained.2.Transcriptome sequencing was used to screen the different expression of MYB transcription factors before and after 300 m M salt stress,and the 13 genes significantly up-regulated in root were verified by q PCR.There are six MYB genes,of which the relative expression was over 10-fold under the salt treatment comparing to that under the normal condition.According to their evolutionary relationship with Arabidopsis thaliana,these genes were named as CeMYB80,CeMYB2,CeMYB15,CeMYB62,CeMYB110 and CeMYB58,respectively.3.The analysis of the promoter region of these genes showed that they all contained ABRE elements,indicating that these genes maybe activated by ABA signaling pathway.4.The results of subcellular localization showed that CeMYB80,CeMYB2,CeMYB62,CeMYB110 and CeMYB58 were located in the nucleus,which was consistent with the characteristics of transcription factor proteins.5.Overexpression vectors of the six genes were constructed and transformed into Arabidopsis thaliana,and two transformation systems for C.equisetifolia mediated by A.tumefaciens and A.rhizogene.were widely used.Transgenic hairy roots proved that the transgenic hairy roots showed no significant difference in plant growth under normal conditions.Under salt treatment,the shoots of control plants with empty vector grew solwly,and presented obvious wilting and yellow,while the stem tips expressing 35S::CeMYB80-GFP and 35S:: CeMYB2-GFP were partly yellow,and the whole was green,showing stronger salt tolerance than the control.The results showed that CeMYB80 and CeMYB2 may be involved in the regulation of the salt tolerance mechanism of Casuarina.