Diverse function of the PISTILLATA, APETALA 3, and AGAMOUS-like MADS-box genes involved in the floral development in Alpinia hainanensis (Zingiberaceae)

Abstract

Zingiberaceae is the vital clue and key node in the decreased process of fertile stamens in Zingiberales, helping to understand the evolution of the ginger families. This study focuses on Alpinia hainanensis to investigate the function of B- and C-class MADS-box genes in floral development. The introns size of two B-class genes AhPI and AhAP3, and one C-class gene AhAG are quite variable. By contrast, the positions of the corresponding introns are conserved, resulting in a similar exon size in homologs. The typical region 70 bp-CCAATCA element was not found in the second intron of AhAG compared to AG homologs. The subcellular localization showed that AhAP3 was in both intranuclear and extranuclear. The heterodimer was formed between APETALA3 and PISTILLATA but not between the B- and C-class proteins using Y2H and BiFC. The 35S::AhAG heterologous transformed Arabidopsis had curly and smaller rosette leaves with early flowering. Floral organs had no homeotic conversion, albeit sepals and petals reduced in size. Siliques development was affected and displayed wrinkled and shorter. By contrast, 35S::AhAP3 and 35S::AhPI did not show any modified phenotype in transgenic Arabidopsis thaliana. We first proposed the model for Alpinia flower development. MADS-box transcription factor binding at particular genomic locations and interaction with partners may be crucial for the development of the floral organ.