A genomic and expression compendium of the expanded PEBP gene family from maize.

Olga N Danilevskaya,Evgueni V Ananiev,Carl R Simmons,Xin Meng,Zhenglin Hou

doi:10.1104/pp.107.109538

Abstract

The phosphatidylethanolamine-binding proteins (PEBPs) represent an ancient protein family found across the biosphere. In animals they are known to act as kinase and serine protease inhibitors controlling cell growth and differentiation. In plants the most extensively studied PEBP genes, the Arabidopsis (Arabidopsis thaliana) FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) genes, function, respectively, as a promoter and a repressor of the floral transition. Twenty-five maize (Zea mays) genes that encode PEBP-like proteins, likely the entire gene family, were identified and named Zea mays CENTRORADIALIS (ZCN), after the first described plant PEBP gene from Antirrhinum. The maize family is expanded relative to eudicots (typically six to eight genes) and rice (Oryza sativa; 19 genes). Genomic structures, map locations, and syntenous relationships with rice were determined for 24 of the maize ZCN genes. Phylogenetic analysis assigned the maize ZCN proteins to three major subfamilies: TFL1-like (six members), MOTHER OF FT AND TFL1-like (three), and FT-like (15). Expression analysis demonstrated transcription for at least 21 ZCN genes, many with developmentally specific patterns and some having alternatively spliced transcripts. Expression patterns and protein structural analysis identified maize candidates likely having conserved gene function of TFL1. Expression patterns and interaction of the ZCN8 protein with the floral activator DLF1 in the yeast (Saccharomyces cerevisiae) two-hybrid assay strongly supports that ZCN8 plays an orthologous FT function in maize. The expression of other ZCN genes in roots, kernels, and flowers implies their involvement in diverse developmental processes.

Highlights

The phosphatidylethanolamine-binding proteins (PEBPs) represent an ancient protein family found across the biosphere
The final number of Zea mays CENTRORADIALIS (ZCN) genes will be established upon completion of the maize genome sequencing project
The nearest genetic markers for each ZCN gene were determined from bacterial artificial chromosome (BAC) contigs and used to position the ZCN genes on the maize genetic map (Table I; Fig. 1)

Summary

Introduction

The phosphatidylethanolamine-binding proteins (PEBPs) represent an ancient protein family found across the biosphere. Plant PEBP-related genes were originally cloned from mutants with altered inflorescence architecture These include Antirrhinum CENTRORADIALIS (CEN; Bradley et al, 1996), Arabidopsis (Arabidopsis thaliana) TERMINAL FLOWER1 (TFL1; Bradley et al, 1997), and tomato (Solanum lycopersicum) SELF PRUNING (SP; Pnueli et al, 1998). The FT gene is transcribed in the leaf phloem (Takada and Goto, 2003), but the FT protein moves via the phloem to the shoot apex where it acts as a floral stimulus This protein provides a molecular explanation for the long hypothesized mobile flowering signal, known as the florigen (Corbesier et al, 2007; Jaeger and Wigge, 2007; Mathieu et al, 2007). The FT protein interacts with the bZIP transcription factor FLOWERING LOCUS D (FD), and together they activate the meristem identity gene APETALA1, a MADS-box protein, triggering flower development (Abe et al, 2005; Wigge et al, 2005)

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Conclusion