TCP Genes Involved in Orchid Ovule Development

TEOSINTE-BRANCHED/CYCLOIDEA/PCF (TCP) proteins are plant-specific transcription factors known to act in multiple aspects of plant growth and development at the cellular, organ and tissue levels. However, no related study has been performed of TCPs in orchids. In this study, we identified 23 TCP genes from the genome sequence of Phalaenopsis equestris. Phylogenetic analysis distinguished two homology classes of PeTCP transcription factor families: classes I and II. Class II was further divided into two subclasses, CIN and CYC/TB1. Spatial and temporal expression analysis showed that PePCF10 predominantly expressed in ovules at early developmental stages and PeCIN8 had high expression at late developmental stages in ovules, with overlapped expression at 16 day after pollination. Subcellular localization and protein–protein interaction analyses revealed that PePCF10 and PeCIN8 could form homodimers and localize in the nucleus. However, PePCF10 and PeCIN8 could not form heterodimers. In transgenic Arabidopsis thaliana plants (overexpression and SRDX, a super repression motif derived from the EAR-motif of the repression domain of tobacco ETHYLENE-RESPONSIVE ELEMENT-BINDING FACTOR 3 and SUPERMAN, dominantly repressed), the two genes helped regulate cell proliferation. Together, these results suggest that PePCF10 and PeCIN8 play important roles in orchid ovule development by modulating cell division.