Flower color variegation caused by alternative splicing of a stuctural gene of flavonoid biosynthetic pathway in Prunus Persica

Variegated plants are highly valuable in the floricultural market, yet the genetic mechanism underlying this attractive phenomenon has not been completely elucidated. In this paper, we identified and measured the different compounds in the variegated flower petals of peach by HPLC and LC/MS analyses. We also sequenced and analyzed the key structural genes in the anthocyanin biosynthesis pathway. We detected that the transcript of ANS gene in white petals contained a 129bp sequence that lacked in the transcript of pink petals, which associated with an intron-retention type of alternative splicing of the ANS gene. This sequence was found to have high GC content with weak splice sites. Retention of this sequence diminished the affinity of translated protein to ferric ion due to the loss of FE 2:1 ligand, and resulted in a dysfunctional enzyme. As a result, we detected virtually no cyanidin-based and pelargonidin-based anthocyanins in white petals. The consequence of ANS dysfunction was further examined by qRT-PCR analysis. This study is the first report that flower color variegation is triggered by the intron-retention type of alternative splicing at molecular level. Findings in this study might represent an important mechanism underlying flower color variegation.