Expression Profiles And Functional Analysis Of Four MebZIPs Members In Cassava

Cassava is a tropical crop with high yield and high starch accumulation.It’s an important source of industrial starch and fuel alcohol,a vital source of food in global hot zones.Among transcription factor families,basic leucine zipper(bZIP)transcription factors are of the largest and widely distributed ones,playing an important role in plant growth and biological accumulation.However,there were few studies about MebZIP,and the information of MebZIP members which regulate the metabolism of storage starch is vacant.The purpose of this study is to explore the role of MebZIP in starch synthesis pathway.The results are as follows:1.We found 104 MebZIP members totally in cassava.Based oncassava transcriptome analysis,we selected ten MebZIPs whose transcription activity in cultivar tubor root(KU50 SC8 and Arg7)were 1.42-185 times than wild type(W14).We named MebZIPI-MebZIP10 according to the genetic ID.Relative expression of ten MebZIP genes were confirmed by real-time fluorescent quantitative PCR:MebZIP3,ebZIP4,MebZIP7,MebZIP8 and MebZIP9 were significantly higher expressed in storage root of the cultivar than in wild species;In functional leaves,the expression of MebZIP2 was little,and the relative expression of MebZIP4,MebZIP9 and MebZIP10 in cultivated species were higher than in wild species.2.MebZIP quickly responded to ABA,and transcriptional level was instantaneously increased in leaves and roots.The relative expression of MebZIP1,MebZIP7 and MebZIP10 reached to a peak one hour later after treatment with ABA in leaves and roots.MebZIP8 and MebZIP9 had high expression levels respectively at 1h and 6h in leaves.3.Expression patterns of four MebZIP members in different development periods and tissues of cultivated and wild cassava showed that MebZIP9 and MebZIPIO expressed higher in roots and leaves of cultivated cassava than the wild during the tubor formation.MebZIP7,MebZIP9,and MebZIP10 showed higher expression levels in root,leaf and stem of cultivated cassava than W14 during tuber root enlargement.Particularly,MebZIP9 had higher expression levels in roots and leaves of cultivated cassava than wild type at the same developmental stages.4.Four MebZIP genes responded to abiotic stress such as PEG,salt,low temperature and high temperature.MebZIP7 was up-regulated by PEG,salt and high temperature.MebZIP8 was inducedto express high in leaves by salt and high temperature in the early treatment.MebZIP9 was induced by salt and high temperature,and the expression in leaves was down-regulated by low temperature.The expression of MebZIP10 was inhibited by high temperature.5.Partial of MebZIP transgenic plants had higher tuber dry matter rate than the wild type,including MebZIP7-21,40,MebZIP8-2,6,21,32,MebZIP9-8,20,23,MebZIP10-3,22,23,40,43,45.The results of potato transformation showed that MebZIP could increase the content of tuber starch,so it is concluded that MebZIP was involved in regulating the synthesis of cassava root starch.6.The potato transformation test showed that the contents of tuber starch,amylose and amylopectin in some MebZIP transgenic plants increased in different degrees.Two transgenic lines of MebZIP7 were significantly higher in starch,amylose and amylopectin than in the wild type,and the content of starch was significantly higher than wild,with 1.2 and 1.5-fold than the wild respectively.About two-thirds of MebZIP8 transgenic plants had higher starch content than wild-type plants.Transgenic plants MebZIP9-8,9,and 20 were significantly higher than wild type,with 1.2 and 1.5-fold of wild respectively.There were 8 lines of MebZIP10 transgenic plants that had significantly higher starch than the wild type,with 1.1 to 1.4-fold.The starch content of MebZIP10-3,7 and 43 were 1.3 times more than that of the wild type.The content of raw sugar in transgenic plants tuber was basically unchanged compared with the wild type.The expression of starch synthesis-related genes were improved in transgenic potato plants.7.Cassava transformation:We Constructed overexpression and RNAi interference vectors of MebZIP7 and MebZIP9 and transformed these vectors into cassava.At present the transgenic plants are at bud stage,and the following experiments are being carried out.