Differential morphology and transcriptome profile between the incompletely fused carpels ovary and its wild-type in maize.

Hongping Li,Jianfeng Chang,Yufeng Wu,Xiuli Hu,Yali Zhao,Chaohai Li,Qun Wang,Pengfei Dong,Moubiao Zhang

doi:10.1038/srep32652

Hongping Li, Jianfeng Chang + Show 7 more

Open Access

https://doi.org/10.1038/srep32652

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Abstract

We have isolated a new mutation in maize, incompletely fused carpels (ifc), which results in an open stylar canal on the ovary and an incomplete pericarp at the top of the kernel. The maize ovary derives from the fusion of three carpels; however, the molecular networks regulating maize carpel fusion remain largely unclear. In this study, RNA sequencing (RNA-seq) was performed on wild-type (WT) and ifc ovaries that were collected after carpel fusion defects could be morphologically distinguished. In total, 877 differentially expressed genes were identified. Functional analysis revealed overexpression of genes related to “DNA binding”, “transcription regulation”, “hormones”, and “stress responses”. Among the 88 differentially expressed transcription factor (TF) genes, five showed a high degree of conservation (77.7–88.0% amino acid identity) of their conserved domains with genes associated with carpel fusion deficiency in Arabidopsis thaliana, suggesting that these five genes might control carpel fusion in maize. In addition, 30 genes encoding components of hormone synthesis and signaling pathways were differentially expressed between ifc and WT ovaries, indicating complex hormonal regulation during carpel fusion. These results help elucidate the underlying mechanisms that regulate carpel fusion, supporting the functional analysis of genes involved in producing this phenotype.

Highlights

One is mediated by the class C gene AGAMOUS (AG)[8], and class E or SEPALLATA genes, as described in the expanded ABC model[9]; the second is an AG-independent pathway involving SPT and CRC genes[10], both of which are negatively regulated by class A genes[11], such as APETALA2 (AP2) and LEUNIG (LUG)[12,13,14]
In maize (Zea mays L.), much less is known than in Arabidopsis about the gene regulatory networks that regulate the differentiation and determine the congenital fusion of the carpels. This is because there are very few known mutations with a phenotype restricted to the carpel, some aspects of carpel tissue development are conserved in Arabidopsis
Genes involved in the auxin pathway play a key role in the regulation of carpel development and gynoecium patterning[20,21], and there is increasing evidence of involvement of auxin biosynthesis and signaling in floral tissue development in Arabidopsis[22]

Summary

Introduction

One is mediated by the class C gene AGAMOUS (AG)[8], and class E or SEPALLATA genes, as described in the expanded ABC model[9]; the second is an AG-independent pathway involving SPT and CRC genes[10], both of which are negatively regulated by class A genes[11], such as APETALA2 (AP2) and LEUNIG (LUG)[12,13,14]. In maize (Zea mays L.), much less is known than in Arabidopsis about the gene regulatory networks that regulate the differentiation and determine the congenital fusion of the carpels. This is because there are very few known mutations with a phenotype restricted to the carpel, some aspects of carpel tissue development are conserved in Arabidopsis. Mutations in kn[1] result in extra carpels with proliferating ovule tissue[4] These genes provide a framework for the molecular regulation of pistil development in maize and indicate the existence of distinct genes and regulatory programs restricted to carpel development. We report a preliminary atlas of the transcriptome characteristics of ifc and wild-type ovaries to begin to decipher carpel development and, to provide fundamental insight into the underlying mechanisms that determine ovary formation, grain yield, and seed quality

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