Cloning And Functional Characterization Of The Key Genes Of Strigolactone Synthetic And Signaling Transduction Pathway In Clonal 84K Poplar

Strigolactones (SLs) are recently characterized carotenoid-derived phytohormones. They play multiple roles in plant architecture. Studies of branching mutants in arabidopsis, pea, rice and petunia have identified several key genes involved in strigolactone biosynthesis or signaling pathway. In Arabidopsis, MAX1, MAX2, MAX3 and MAX4 are four founding members of strigolactone pathway genes. However, little is known about the strigolactone pathway genes in trees. In this study, the sequence homologues for each MAX protein in clonal 84K poplar were identified and their function in regulating shoot branching were analysed, the results were as follow:1. Four genes, including KPtrMAX1, KPtrMAX2, KPtrCCD7 and KPtrCCD8 were cloned, respectively, the coding regions of four genes were from 1590 bp to 2106bp in length, encode proteins of which varying from 529 to 701aa.2. In order to determine whether KPtrMAXl gene, KPtrMAX2 gene, KPtrCCD7 gene and KPtrCCD8 gene were functionally conserved, each ORF driven by the 35S promoter was expressed in the corresponding Arabidopsis max mutant individually. The results indicated that KPtrMAX1, KPtrMAX2, KPtrCCD7 and KPtrCCD8 were able to complement or partially complement the shoot branching phenotypes of the corresponding Arabidopsis max mutants.3. Gene expression analysis revealed that KPtrMAX2 is differentially expressed across various tissues and organs. KPtrMAX2 was highly expressed in axillary bud and stem.4. pGWB5 vector containing 35S:KPtrMAX2 plasmid was transformed into clonal 84K poplar. Semi-quantitative RT-PCR analysis revealed the expression of KPtrMAX2 gene in poplar.