Isolation and expression of McF3H gene in the leaves of crabapple

Abstract

The molecular mechanisms involved in leaf color variation were investigated in crabapple. Using the total RNA from the leaves of crabapple ‘Royalty’ as the template, the full cDNA of F3H (Flavanone-3-hydroxylase) gene (1,370 bp) was cloned by reverse transcription polymerase chain reaction and rapid-amplification of cDNA ends. The gene was named as McF3H, containing a 1,092-bp open reading frame encoding a protein of 364 amino acids. Corresponding genomic DNA sequence was 1,983 bp, containing two introns, and all the cleave sites obeyed the GT–AG rule. The expression of McF3H gene following leaf development was determined by real-time quantitative PCR in the leaves of three crabapple varieties, ‘Flame’ (both young and mature leaves are green), ‘Radiant’ (young leaves are orange to red and mature leaves are green) and ‘Royalty’ (both young and mature leaves are red to purple). The results showed that McF3H gene was expressed in both red and green leaves. But the expression levels of McF3H gene in ever-red-leafed ‘Royalty’ were significantly higher than in evergreen-leafed ‘Flame’ at all stages of leaf development. The transcript level in ‘Radiant’ showed the similar temporal pattern to the variation of leaf color following its leaf development. Also, the anthocyanin accumulation levels in crabapple leaves were consistent with the color variation of leaves. These results suggest that McF3H gene is one of the important structure genes related to anthocyanin accumulation in crabapple leaves and the red coloration of crabapple leaf is associated with high expression level of this gene.