Abstract:

A floral mutant was obtained during the construction of a mutant library with Petunia hybrida W138 strain，which was mainly characterized by abnormal development of sepals and petals，and named as aps（abnormal petals and sepals）. Compared with normal W138 plant（Wt），the most obvious phenotype of aps is its split corolla，usually with three lobes；simultaneously，two of five sepals in aps mutant are petaloid. Scanning electron microscopy（SEM）analysis indicated that the shape of epidermis cells in the petaloid sepals of aps plants was the same as that in petals of Wt plants. The genetic analysis by selfing，crossing，and backcrossing between aps and its normal sister plants or W115 suggested that the trait of aps is controlled by a single recessive gene. qPCR was used to analyze the expression of floral development related genes in four whorls of organs between aps and Wt flowers. The results showed that three B-class genes（FBP1，PMADS1 and PMADS2）and some E-class genes（FBP2，FBP4 and FBP5）was activated in petaloid sepals of aps mutants，however，the expression of all A-class genes including FBP26，FBP29，PEG，AP2A，AP2B and AP2C，as well as the E-class genes FBP9 and FBP23，are down-regulated in this whorl. In aps petals，except for FBP29 that is not expressed in petals，all other A-class genes are up-regulated，as are the B-class genes，FBP1 and PMADS2，and the E-class genes FBP2，FBP5，FBP23 and PMADS12. The expression of C- and D-class genes are not altered in sepals and petals of the mutants，but both C-class genes are downregulated in stamens and styles of aps plants，like the D-class gene FBP7 in ovaries. The characterization of aps mutant provides a good chance for studying the molecular regulation of floral organ development and for exploring the relationship of floral genes in petunia.

Key words: petunia, floral organ, development, mutant, petaloid sepal, split corolla, MADS-box