Expression Patterns And Functional Analysis Of VERNALIZATION1Gene In Brachypodium Distachyon L

The wheat (Triticun aestivum L.) is one of the most important grain crops in the world.Its research of growth and development attracts many scientists vision. In the growth of wheat,the most important is undoubtedly the flowering of wheat. Vernalization could induce andpromote the overwintering plants into flower induction. So far, many genes associated withvernalization have been found, such as VRN1, VRN2, VRN3and VRT2. VRN1is the key genein response to vernalization of wheat, so the research of characteristic and function of VRN1iscrucial for the research of vernalization mechanism which is mediated by VRN1in wheat.Although it is direct to study the characteristic and function of genes by wheat, wheat ishexaploid field crops. It has a long growth cycle, a large genome, universal repeat sequences,difficile genetic transformation, causing the vernalization mechanism which is mediated byVRN1has not been clear until now. Brachypodium distachyon has so many favorableconditions, such as a short growth cycle, a close relationship with wheat, and could be easilytransformed, that has become the new model material for Gramineae. In our study we selectthe Brachypodium distachyon Bd21ecotype as our material.We isolated the homologous gene of wheat crops VRN1from Brachypodium Bd21ecotype and named as BdVRN1. We analyzed the expressive features and had a preliminaryanalysis for the function of BdVRN1.(1) The analysis of the genome of BdVRN1shows that BdVRN1locates in thechromosome1and has eight exons and seven introns. The gene ID is Bradi1g08340.1and thelength of genome is9832bp. The cDNA of BdVRN1is732bp, encoding243amino acid. It isworth mentioning that there is a relatively large intron in BdVRN1which is similar with otherflowering genes in wheat crops.(2) The analysis of the amino acid sequences of BdVRN1shows that BdVRN1is typicalgene belonging to MADS-box family which is associated with flowering time. The comparative analysis of amino acid sequences among BdVRN1, TaVRN1and AtAP1showsthat the regions in MADS-box and K-box domain are highly homologous while the positionsin3’ end are relatively specific.(3) The expressive characteristic analysis of BdVRN1in the length of daylight shows thatthe expression levels of BdVRN1gradually improved along with the growth of plants underlong-day condition and always are in a low level under short-day condition. All these provethat the expression of BdVRN1is regulated by photoperiod.(4) The expressive characteristic analysis of BdVRN1in vernalization conditions showsthat the expression levels are increased with the prolongation of vernalization time under nomatter long days or short days. However, there are different degrees of decline afer back intogreenhouse. Nevertheless the expression level of BdVRN1under long days is still higher thanthe level under short days. All these prove that the expression of BdVRN1is indeed regulatedby vernalization and photoperiod.(5) The expressive characteristic analysis of BdVRN1for circadian rhythm shows that theexpression levels of BdVRN1are all presented certain regularity under no matter long days orshort days. The expression levels show a certain degree of rising after into the light, afterabout10hours in the light reaching the highest, followed by the expression level decreased,indicating that the expression of BdVRN1has circadian rhythm.(6) The expression analysis of BdVRN1in different parts of the Bd21ecotype shows thatBdVRN1could be expressed in leaves, stems and spikes and the expressive levels are allincreased in varying degrees after vernalization. Also we find that the expression of BdVRN1in shoot has the most obvious improvement.(7) Through the analysis of the function of BdVRN1, we found when BdVRN1wasover-expressed, the Brachypodium occured extremely early flowering phenomenon. Thestructures of floral organs are consistent between early flowering plants and wild type,indicating that over-expression of BdVRN1can promote flowering, but does not affect thedevelopment of the floral organs. All those prove that BdVRN1is a pure gene that couldpromote flowering without affecting floral organ development. But early flowering plants cannot be normal fructified because the pollen in early flowering plants could not normally loosepowder. (8) Through the analysis of the phenotype which is formed by over-expressed BdVRN1in Rice, we found that over-expression of BdVRN1in ZH11could not appear the extremelyearly flowering phenomenon and could be normal fructified. Our study speculates that theflowering pathway which is mediated by BdVRN1is not going to work in rice and may be aunique flowering pathway in the temperate Gramineae.