Screening Candidate Genes at the Co Locus Conferring to the Columnar Growth Habit in Apple ( Malus × Domestica Borkh.)

The columnar growth trait of apple ( × Borkh.) is genetically controlled by the Columnar ( ) locus on 10 chromosomes, including several candidate genes. Except for , other candidate genes at the locus are less elucidated. In this study, a strategy of step-by-step screening was adopted to select 11 candidate genes by experimental cloning, transient expression, and genetic transformation. There existed several SNPs in four genes by sequence alignment in columnar and non-columnar apples. Two genes were detected in the nucleus and three genes in the cell membrane, other genes were located in multiple cellular structures by subcellular location. Ectopic expression demonstrated that more branching occurred in -OE by upregulating and and enlarged leaves in -OE tobaccos by upregulating . Transcripts of and were associated with the genotypes in apples. The results indicate that and are involved in the columnar growth phenotype in apple, probably through altering polar auxin transport, active gibberellin levels, and strigolactone biosynthesis.