The Cloning, Expression And Flowring Regulation Mechanism Of Related Genes LFY, TFL1 And FT In Pyrus

To elucidate the expression characteristics of early flowering regulatory genes and the effects of different cultivation measures on flowering of pear, we cloned the genes of LFY, TFL1 and FT, discussed the expression profiles of the flowering related genes. Based on the branch and auxin treatment, we analysed the flower formation rate, the expression of early flowering regulatory gene and the effects of auxin treatment on nutrition content. Details were listed as followed:1. In this study, the genes of LFY(PbLFY), TFL1(PbTFLl; KF240776) and FT(PbFT; KF240775) were cloned from ’Jingzhui’ pear (Pyrus bretschneider). Meanwhile, the full length of FT DNA sequence was cloned, which contained four exons and three introns. PbLFY, PbTFL1 and PbFT contained a PEBP domain. The homology between PbTFLl and PbFT reached 60%, theybelongs to an FT/TFL1 gene family owning different conserved sites. In evolution, these three genes are highly conserved, especially LFY gene. TFL1 gene and FT gene had different evolution modes. TFL1 had a faster evolution than FT. TFL1 showed a greater differentiation. The nature of the protein, and the secondary structure of the three genes showed their characteristics. LFY is an acid labile protein, which contains two hydrophobic domains. TFL1 and FT are alkaline stable proteins and have no transmembrane domain.2. Combined with the results of paraffin section, the expression profiles of the three genes under different tissues and different periods of floral bud development were examined by Real-time quantitative PCR (qPCR). The results showed that the transcript level of PbLFY was the highest in floral bud, but was not detected in young leaf and stamen, which showed a higher expression of PbLFY at the beginning of bud differentation, and kept an increasing level until reaching the highest level when floral organ primordia appeared. Steady-state mRNA level of PbTFLl was the highest in floral bud, but was not observed in young leaf, mature flower and floral organs. PbTFL1 transcript level reached the highest at the beginning of floral bud development, which exhibited a decrease gradually, then decreased extremely at the beginning of floral bud differentiation, PbFT transcriptions were detected in all tissues, the highest level was in mature leaf andfollowed by floral bud. The transcript level of PbFT was lower at the early stage of floral bud development, and then increased steadily until reaching the highest level at the beginning of floral differentiation.3. To elucidate the effects of branch bending on the expression of early flowering regulatory gene and the contents of endogenous hormone and nutrition, we branched bending with a 90° in spring on ’Cuiguan’ pear (Pyrus Pyrifolia). The results showed that branch bending improved the flower formation rate. The transcript levels of flowering promoting genes, PbLFY and PbFT rose, while the transcript levels of flowering suppression gene PbTFL1 decreased. The content of promoting floral differentiation hormone ZT and ABA increased, while the content of floral suppression differentiation hormone GA3 and IAA decreased. During the floral differentiation, starch was accumulated, and the C/N increased. The analysis of correlation showed that genes, endogenous hormone and nutrient interacted each other.4. In this experiment, we sprayed hormone on the five-year-old ’Mantianhong’× ’Dangshansu’ none flowered seedlings during the bud differentiation. Treatment group Ⅰ was sprayed with 6-BA, treatment group Ⅱ was sprayed with Eth, treatment group Ⅲ was sprayed with a mixture of both, and the CK was sprayed with water. The results showed that:hormone treatment can promote flowering and the total number of flower buds had increased significantly compared with CK. Treatment group Ⅲ, and treatment group Ⅰ were better than the treatment group Ⅱ. Hormone promoted flowering was due to the key genes for early flowering, endogenous hormone and nutrient. The transcript levels of PbLFY and PbFT rose after the hormone treatment, while the transcript levels of PbTFL1 decreased. The content of hormone ZT and ABA which promoting floral differentiation increased, while the content of floral suppression differentiation hormone GA3 and IAA decreased. During the floral differentiation, starch was accumulated, meanwhile C/N increased.