Abstract
TEOSINTE-BRANCHED/CYCLOIDEA/PCF (TCP) proteins are plant-specific transcription factors known to have a role in multiple aspects of plant growth and development at the cellular, organ and tissue levels. However, there has been no related study of TCPs in orchids. Here 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 was predominantly expressed in ovules at early developmental stages and PeCIN8 had high expression at late developmental stages in ovules, with overlapping expression at day 16 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.
Highlights
Plant architecture and organ shape depends on complex coordination of cell proliferation and cell differentiation in response to genetic and environmental cues (Ingram and Waite, 2006; Kieffer et al, 2011)
These results suggest that PePCF10 and PeCIN8 play important roles in orchid ovule development by modulating cell division
To identify TCP transcription factor (TF) coding genes, the hidden Markov model (HMM) profile of the TCP domain (PF03634) was blast searched in the P. equestris genome (Cai et al, 2015)
Summary
Plant architecture and organ shape depends on complex coordination of cell proliferation and cell differentiation in response to genetic and environmental cues (Ingram and Waite, 2006; Kieffer et al, 2011). The final shape of shoot lateral organs, leaves and flowers is determined by coordinated growth after the initiation of primordia from shoot meristems in seed plants This coordination involves the complex behavior of many transcription factors (TFs). The TCP gene family was first described in 1999 and named after the first three characterized members, TEOSINTE BRANCHED1 (TB1) in maize, CYCLOIDEA (CYC) in snapdragon, and Proliferating Cell Factor (PCF) in rice (Cubas et al, 1999). They are ancient plant-specific TFs that originated near the base of streptophytes about 650– 800 million years ago (Mondragon-Palomino and Trontin, 2011). Several class II TCP members share an arginine-rich R domain and an ECE motif (a glutamic acid– cysteine–glutamic acid stretch), both of unknown biological function (Martín-Trillo and Cubas, 2010)
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