Abstract:

【Objective】 The PISTILLATA（PI）gene belongs to the typical type II MADS-box gene family and is a class B gene in the ABC（D）E model, and plays an important role in plant development. However, functions of the PI homologous genes in pepper（Capsicum annuum L.）have not been reported. This study explored the function of pepper PI gene, laying a foundation for in-depth research on the functional mechanism of plant PI homologs.【Method】 We cloned a PI homologous gene CaPI from the cDNA of floral organ tissues of pepper using RT-PCR, and analyzed its physicochemical properties, subcellular localization, protein structure, and phylogenetic relationship through bioinformatics methods. The expression pattern of CaPI in different tissues of pepper was performed using real-time quantitative PCR（RT-qPCR）method. A plant overexpression vector of 35S:CaPI was constructed and transformed into Arabidopsis using floral-dipping method.【Result】 The CaPI gene contains an open reading frame of 648 bp and encodes a peptide of 215 amino acids with a relative molecular weight of 25.13 kD. Multiple amino acid sequence alignment indicated that the N-terminus of CaPI contains a conserved motif of ‘MGRGKIEIKRIEN’. Phylogenetic tree analysis with homologous proteins of other species showed that the CaPI gene was closely related to the PI homologous genes of potato, tomato, and petunia. The RT-qPCR analysis showed that CaPI was predominantly expressed in flowers, with the highest expression level in the sepals, followed by petals, with low expression in stamens and almost no expression in pistils. The overexpression of CaPI in Arabidopsis revealed that, compared to wild type（Col-0）plant, the 35S:CaPI transgenic plants exhibited phenotypes such as increased number of rosette leaves and branches, but did not affect the development of floral organs.【Conclusion】 CaPI in the pepper functions in promoting plant branching development.

Key words: CaPI, Capsicum annuum L., MADS-box, gene expression