| Winter wheat is planted in autumn,undergo a long period of low temperature stress(Vernalization),and blossom and bear fruit in the following spring.Vernalization is a necessary process for the transition from vegetative growth to reproductive growth of winter wheat,but also plays an important role in the subsequent growth and development of wheat as well as the final yield.Thousand kernel weight,spike number per square meter and kernel number per spike are three important factors affecting yield.Thousand kernel weight and kernel number per spike were affected by the spike architecture.The number of spikelet is an important factor to determine the spike architecture in wheat.In order to investigate the effect of vernalization duration on the spikelet number of common wheat(Triticum aestivum L.),we firstly confirmed the minimum vernalization time requirement for Jimai 22 under 4 °C.We found that 26-day vernalization was the minimum requirment for Jimai 22 to complete its growth and development.Statistic analysis revealed that the number of spikelet in the main tillers of Jimai 22 was significantly decreased at first and then gradual with the elongation of vernalization duration.Plants under 26-day vernalization produced the largest number of spikelet.Observing the development of the SAM,we found that the duration time from the elongation stage to the double ridge stage gradually became shorter with the elongation of vernalization duration,which could be the reason for the decrease in the number of spikelet in wheat.We performed RNA-seq analysis on the shoot apical meristem(SAM)of seedlings under three vernalization duration(26d,33 d,and 40d).RNA-seq analysis revealed that the expression of 3142 genes in the SAM was significantly changed.These differentially expressed genes(DEGs)are enriched in the process of nucleosome assembly and chromosome assembly.A total of 733 DEGs(including 192 up-regulated expression genes and 541 down-regulated expression genes)showed a similar expression changes with those of spikelet numbers.GO and KEGG enrichment analysis showed that these DEGs were closely related to transcriptional regulation,jasmonic acid metabolism and signaling pathways.Thepromoters of these DEGs related to jasmonic acid metabolism and signaling pathways contain the binding sequence of the vernalization-related transcription factor VRN1,CArG box motif.Therefore,we suggest that the jasmonic acid pathway may be related to the vernalization-regulated spikelet number of wheat.We compared the DEGs with the identified yield-related QTL,and 65 candidate genes were identified that may affect the spikelet number of wheat.Furthermore,a subset of DEG genes was selected to construct genetic transformation vectors to explore their functions in spikelet development of wheat.In addition,we cloned and analyzed TFL1-4A,a homologous gene of Arabidopsis thaliana TERMINAL FLOWER 1(TFL1)in wheat.qRT-PCR analysis showed that the gene has the highest expression in spikelets,and in situ hybridization showed that the gene was specifically expressed in the single ridge stage,double ridge stage,spikelet primordium stage and floret differentiation stages of SAM.We constructed an overexpression vector of TFL1-4A gene and transformed it into the Arabidopsis tfl1 mutant,and found that the phenotype of the apex flower of tfl1 could be partially recovered.Therefore,we suggest that TFL1-4A is similar to the AtTFL1 that extends vegetative growth stage and maintains the infinite growth of inflorescence in wheat. |
