The study of two barley Type I-like MADS-boxgenes as potential targets of epigenetic regulation during seed development

Aliki Kapazoglou,Athanasios S Tsaftaris,Vicky Drosou,Ioannis Ganopoulos,Aphrodite Tsaballa,Evangelia D Kouri,Emmanouil Flemetakis,Cawas Engineer,Eleni Tani,Chrysanthi Kalloniati

doi:10.1186/1471-2229-12-166

Abstract

BackgroundMADS-box genes constitute a large family of transcription factors functioning as key regulators of many processes during plant vegetative and reproductive development. Type II MADS-box genes have been intensively investigated and are mostly involved in vegetative and flowering development. A growing number of studies of Type I MADS-box genes in Arabidopsis, have assigned crucial roles for these genes in gamete and seed development and have demonstrated that a number of Type I MADS-box genes are epigenetically regulated by DNA methylation and histone modifications. However, reports on agronomically important cereals such as barley and wheat are scarce.ResultsHere we report the identification and characterization of two Type I-like MADS-box genes, from barley (Hordeum vulgare), a monocot cereal crop of high agronomic importance. Protein sequence and phylogenetic analysis showed that the putative proteins are related to Type I MADS-box proteins, and classified them in a distinct cereal clade. Significant differences in gene expression among seed developmental stages and between barley cultivars with varying seed size were revealed for both genes. One of these genes was shown to be induced by the seed development- and stress-related hormones ABA and JA whereas in situ hybridizations localized the other gene to specific endosperm sub-compartments. The genomic organization of the latter has high conservation with the cereal Type I-like MADS-box homologues and the chromosomal position of both genes is close to markers associated with seed quality traits. DNA methylation differences are present in the upstream and downstream regulatory regions of the barley Type I-like MADS-box genes in two different developmental stages and in response to ABA treatment which may be associated with gene expression differences.ConclusionsTwo barley MADS-box genes were studied that are related to Type I MADS-box genes. Differential expression in different seed developmental stages as well as in barley cultivars with different seed size was evidenced for both genes. The two barley Type I MADS-box genes were found to be induced by ABA and JA. DNA methylation differences in different seed developmental stages and after exogenous application of ABA is suggestive of epigenetic regulation of gene expression. The study of barley Type I-like MADS-box genes extends our investigations of gene regulation during endosperm and seed development in a monocot crop like barley.

Highlights

MADS-box genes constitute a large family of transcription factors functioning as key regulators of many processes during plant vegetative and reproductive development
In our recent study on the identification and characterization of two SOC1-like gene homologues from barley [44] it was shown that two HvSOC1-like proteins containing the K-box domain are closely related to the Type II MADS-box proteins whereas they are more distantly related to ODDSOC1 and ODDSOC2
Phylogenetic analysis showed that the two barley Type I-like MADS-box proteins together with their putative orthologues from wheat (TaAGL-33 and TaAGL-42), brachypodium (Bradi2g59190, Bradi2g59120), rice (OsMADS65) and maize (ZmB4FML1), form a cluster which is closer related to the alpha clade of Type I MADS-box proteins (Mα)

Summary

Introduction

MADS-box genes constitute a large family of transcription factors functioning as key regulators of many processes during plant vegetative and reproductive development. Fertilization of the adjacent central cell by a second sperm cell forms a triploid endosperm which supports embryo growth and development by producing storage proteins, lipids and starch [1,2] During this process, a large number of genes are activated. The PHE1 gene is expressed transiently at high levels immediately after fertilization in a parentally imprinted manner where the paternal allele is expressed whereas the maternal allele is silenced [19,20] Both DNA and histone methylation are responsible for these silencing events [19,20,21]. A distantly located region downstream of paternal PHE1 was found to have a DNA methylation requirement for PHE1 expression [22]

Methods

Results

Discussion

Conclusion