Genome-wide identification and classification of MIKC-type MADS-box genes in Streptophyte lineages and expression analyses to reveal their role in seed germination of orchid

Chunmei He,Jaime A Teixeira Da Silva,Can Si,Mingzhi Li,Jun Duan

doi:10.1186/s12870-019-1836-5

Abstract

BackgroundMADS-box genes play crucial roles in plant floral organ formation and plant reproductive development. However, there is still no information on genome-wide identification and classification of MADS-box genes in some representative plant species. A comprehensive investigation of MIKC-type genes in the orchid Dendrobium officinale is still lacking.ResultsHere we conducted a genome-wide analysis of MADS-box proteins from 29 species. In total, 1689 MADS-box proteins were identified. Two types of MADS-box genes, termed type I and II, were found in land plants, but not in liverwort. The SQUA, DEF/GLO, AG and SEP subfamilies existed in all the tested flowering plants, while SQUA was absent in the gymnosperm Ginkgo biloba, and no genes of the four subfamilies were found in a charophyte, liverwort, mosses, or lycophyte. This strongly corroborates the notion that clades of floral organ identity genes led to the evolution of flower development in flowering plants. Nine subfamilies of MIKCC genes were present in two orchids, D. officinale and Phalaenopsis equestris, while the TM8, FLC, AGL15 and AGL12 subfamilies may be lost. In addition, the four clades of floral organ identity genes in both orchids displayed a conservative and divergent expression pattern. Only three MIKC-type genes were induced by cold stress in D. officinale while 15 MIKC-type genes showed different levels of expression during seed germination.ConclusionsMIKC-type genes were identified from streptophyte lineages, revealing new insights into their evolution and development relationships. Our results show a novel role of MIKC-type genes in seed germination and provide a useful clue for future research on seed germination in orchids.

Highlights

MADS-box genes play crucial roles in plant floral organ formation and plant reproductive development
Transcription factor (TF) recognize cis-regulatory regions of target genes, regulate their expression in a way that leads to a wide range of physiological and biochemical processes
No MADS-box gene was found in Dunaliella salina, only one MADS-box gene was observed in Micromonas pusilla and in Chlamydomonas reinhardtii, and there were just two MADS-box genes in Volvox carteri (Fig. 1)

Summary

Introduction

MADS-box genes play crucial roles in plant floral organ formation and plant reproductive development. There is still no information on genome-wide identification and classification of MADS-box genes in some representative plant species. The regulation of gene expression is a complex control mechanism that is coordinated by a number of mechanisms, including by transcription factors (TFs). TFs recognize cis-regulatory regions of target genes, regulate their expression in a way that leads to a wide range of physiological and biochemical processes. They modulate developmental processes in plants [1]. MADS-box TFs, an ancient family of TFs found in both green algae charophyceans and land plants, play an essential role in the evolution of flower architecture [2, 3].

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