Abstract:

Photoperiod is one of important environmental factors affecting plant bolting and flowering which are regulated by plant phytochrome proteins.The signal network mediated by PHYB has an important inhibitory effect on plant bolting and flowering.Previous studies revealed that there were large segment insertion/deletion differences between the PHYB gene promoter of the Chinese cabbage late-bolting line 06-247 and the easy-bolting line He102.In order to further investigate the impact of promoter mutation on PHYB and the key genes of its downstream pathways,this study was conducted.Based on bioinformatics methods,the redundancy characteristics of phytochrome genes in genome Chinese cabbage were firstly analyzed.It was found that the Chinese cabbage genome contained six phytochrome genes,of which PHYA had two copies,and PHYB,PHYC,PHYD,and PHYE all had only one copy.Then amino acid sequence alignment was used for screening of the specific sequence of PHYB.Antigenic determination clusters were designed based on the specific sequence and the antibodies against PHYB was prepared.The fluorescence quantitative RT-PCR technology and Western Blot technology were used to study the relative content of PHYB in 06-247 and He102.At the same time,the dynamic changes of key regulatory genes such as CCA1,FLC,CO and FT which in the downstream of PHYB pathway were also compared.The results showed that the promoter mutation caused significant differences both in level of mRNA in 06-247 and then significantly increased the protein level of PHYB.At the same time,the downstream regulatory genes such as CCA1,FLC,CO and FT were highly expressed in 06-247,which had an important impact on bolting resistance of 06-247.

Key words: Chinese cabbage, Phytochrome B, Photoperiod, Bolting, Western Blot