Histone Acetylation Accompanied with Promoter Sequences Displaying Differential Expression Profiles of B-Class MADS-Box Genes for Phalaenopsis Floral Morphogenesis

Chia-Chi Hsu,Tien-Chih Chen,Wen-Luan Wu,Chun-Wei Yu,Wen-Huei Chen,Hong-Hwa Chen,Pei-Shan Wu,Wen-Chieh Tsai,Keqiang Wu,Zhong-Jian Liu

doi:10.1371/journal.pone.0106033

Chia-Chi Hsu, Tien-Chih Chen + Show 8 more

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https://doi.org/10.1371/journal.pone.0106033

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Abstract

Five B-class MADS-box genes, including four APETALA3 (AP3)-like PeMADS2∼5 and one PISTILLATA (PI)-like PeMADS6, specify the spectacular flower morphology in orchids. The PI-like PeMADS6 ubiquitously expresses in all floral organs. The four AP3-like genes, resulted from two duplication events, express ubiquitously at floral primordia and early floral organ stages, but show distinct expression profiles at late floral organ primordia and floral bud stages. Here, we isolated the upstream sequences of PeMADS2∼6 and studied the regulatory mechanism for their distinct gene expression. Phylogenetic footprinting analysis of the 1.3-kb upstream sequences of AP3-like PeMADS2∼5 showed that their promoter regions have sufficiently diverged and contributed to their subfunctionalization. The amplified promoter sequences of PeMADS2∼6 could drive beta-glucuronidase (GUS) gene expression in all floral organs, similar to their expression at the floral primordia stage. The promoter sequence of PeMADS4, exclusively expressed in lip and column, showed a 1.6∼3-fold higher expression in lip/column than in sepal/petal. Furthermore, we noted a 4.9-fold increase in histone acetylation (H3K9K14ac) in the translation start region of PeMADS4 in lip as compared in petal. All these results suggest that the regulation via the upstream sequences and increased H3K9K14ac level may act synergistically to display distinct expression profiles of the AP3-like genes at late floral organ primordia stage for Phalaenopsis floral morphogenesis.

Highlights

In Arabidopsis thaliana and Antirrhinum majus, the development of different floral organs is controlled by several classes of floral-organ identity genes [1]
The 2,121-bp promoter sequence of PeMADS5 could not be amplified from the genomic DNA of P. equestris by using PCR, and both PeMADS3 and PeMADS4 with the promoter fragments,1.5 kb could not be extended
For the PeMADS4 promoter, a 4.8-kb DNA fragment from BAC clones was recovered and sequenced, which extended its upstream sequence to 3,303 bp (Fig. 1, horizontal line box)

Summary

Introduction

In Arabidopsis thaliana and Antirrhinum majus, the development of different floral organs is controlled by several classes of floral-organ identity genes [1]. All these genes, except AP2 from A. thaliana, belong to the MADS-box family, with a highly conserved 180-bp sequence of the MADS domain that can bind to the conserved CArG-box [CC(A/T)6GG] sequence [2, 3]. Except AP2 from A. thaliana, belong to the MADS-box family, with a highly conserved 180-bp sequence of the MADS domain that can bind to the conserved CArG-box [CC(A/T)6GG] sequence [2, 3] These MADS-box genes were cloned from a wide range of plant species to explain the floral organ development [1, 4,5,6]. Both trimethyl histone H3 lysine-4 (H3K4me3) and acetyl histone H3 (H3Ac) are the active histone markers

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