One novel strawberry MADS-box transcription factor FaMADS1a acts as a negative regulator in fruit ripening

MADS-box genes, which encode highly conserved DNA-binding transcriptional factors, can regulate developmental processes in plants. FaMADS1a has not been functionally analyzed in non-climacteric fruit to date. In this study, one strawberry (Fragaria × ananassa) MADS-box gene, FaMADS1a, was cloned and its tissue-specific expression profiles were analyzed. FaMADS1a expressed in petal and fruit, and its expression levels decreased significantly during fruit ripening. Multiple sequence alignments suggested that FaMADS1a protein exhibited conserved MADS_MEF2_like motif, K-box region, MADS domain, SRF-TF motif and ARG80 domain. Phylogenetic analysis revealed that FaMADS1a belonged to the SEP1/2 clade. Phytohormone abscisic acid (ABA) suppressed FaMADS1a expression but accelerated the ripening process and anthocyanin-related gene expressions, while indole-3-acetic acid (IAA) induced FaMADS1a expression with delayed ripening phenotype and reduced expressions of anthocyanin-related genes. The pBI121 vector-mediated over-expression of FaMADS1a reduced the expressions of four anthocyanin-related genes and delayed fruit ripening compared to the control. Results suggested that FaMADS1a played a negative role in anthocyanin accumulation of strawberry fruit via repressing FaPAL6, FaCHS, FaDFR and FaANS.