Functional Analysis Of The AhMFT In Peanut (Arachis Hypogaea L.) Seed Dormancy

Currently, degree of self-sufficiency in edible oils in China is less than40%.Imported oils bridge the big gap in demand and supply of edible oils. Rising domesticdemand and shortage suply of edible oils challenge oil security in China. As one ofthe most important oil crops, peanut plays vital roles in oil security in our country.However, pre-harvest sprouting (PHS), due to weak seed dormancy, severely reducespeanut yield and quality. Previous studies showed that PHS can cause10-20%yieldloss and the germinated seeds are more susceptible to aspergillus flavus.As a highly conserved member of PEBP, MFT (MOTHER OF FT AND TFL1) is ahomologous gene of FT (FLOWERING LOCUS T) And TFL1(TERMINALFLOWER1). Extensive efforts have revealed that FT and TFL1were key genes in thecontrol of flowering time. FT functions as positive regulators and promotes thetransition of the shoot apical meristem to a flower, while TFL1functions as floweringrepressors and delays the flowering transition. However, functional studies on MFTare still relatively limited. Recently, MFT were shown to promote seed germination inArabidopsis by modulating the ABA signal through a negative feedback. On thecontrary, TaMFT, the wheat homolog of MFT, inhibits seed germination after seedmaturity.The above studies indicate MFT plays important roles in regulation ofgermination. In this study, the AhMFT, peanut homolog of MFT, has been cloned viabioinformatics and RT-PCR methods. The expression profile of AhMFT wereanalyzed by real-time quantitative PCR. We evaluate the germination of transgenicArabidopsis overexpressing AhMFT. The results are as follows:1. Six known PEBP genes in Arabidopsis were used to search peanut ESTdatabase. As a result,44matched EST sequences were obtained. Among them,37ESTs were highly similar to MFT. On the basis of EST origins, these37ESTswere all generated from seeds, which indicated that peanut MFT genes may play important roles in seed development.2. The AhMFT was isolated from penaut cultivar Luhua14by RT-PCR method.AhMFT contains a single open reading frame of531bp in length. The predictedAhMFT protein has176amino acids with an estimated molecular mass of19.19kDa and an isoelectric point of8.93. Sequence analysis indicated that thesimilarity between AhMFT and MFT was72%.3. Expression analysis showed that AhMFT expressed in all tissues examined, butpreferablely in seeds. We also examined the expression pattern of AhMFT in freshharvest seeds, dry mature seeds and germinated seeds and found AhMFT had thehighest expression in germinated seeds.4. At the early stage of seed germination, the germination rate of transgenicArabidopsis overexpressing AhMFT was significantly lower than that ofwild-type plants. However, at the middle and later stage of seed germination,there was no difference in germination rate between transgenic and wildArabidopsis. These results suggested that exogenous AhMFT may inhibit seedgermination.5. Germination-related genes in transgenetic Arabidopsis were analyzed byqRT-PCR. The expression of NCED9, CYP707A2, CYP707A3, GA20ox3, GA30x1,RGL3, ABI3and ABI5were all increased in transgenic Arabidopsis, while RGL3,NCED6and RGL2decreased in transgenic plants. These results indicated AhMFTaffected the expression of ABA and GA metabolism and signaling genes. Takentogether, all these evidences suggested that AhMFT was a negative regulator ofseed germination.