Functional analysis of ZmMADS1a reveals its role in regulating starch biosynthesis in maize endosperm

Qing Dong,Jingjing Kong,Hongjian Chen,Cheng Li,Qianqian Xu,Tingchun Li,Haiyang Jiang,Fang Wang,Beijiu Cheng,Long Chen

doi:10.1038/s41598-019-39612-5

Qing Dong, Jingjing Kong + Show 8 more

Open Access

https://doi.org/10.1038/s41598-019-39612-5

Copy DOI

Abstract

MADS-box family proteins play an important role in grain formation and flower development; however, the molecular mechanisms by which transcription factors regulate the starch metabolism pathway are unclear in maize. Here, we report a transcription factor, ZmMADS1a, that controls starch biosynthesis in maize (Zea mays L.). We demonstrate the expression of ZmMADS1a in tassel, silk, and endosperm, and show that the protein is localized to the cell nucleus. Compared with the control, seeds of overexpressing ZmMADS1a increased starch content (especially amylose content), had smaller starch granules and altered chemical structure. Meanwhile, overexpression of ZmMADS1a resulted in increases in the contents of soluble sugars and reducing sugars in maize. ZmMADS1a plays a positive regulatory role in the starch biosynthesis pathway by up-regulating several starch biosynthesis related genes. We also show that ZmMADS1a has a similar adjustment mechanism of starch biosynthesis in rice. Collectively, our study suggests that ZmMADS1a functions as a positive regulator of starch biosynthesis by regulating the expression of key starch metabolism genes during seed development.

Highlights

Based on domain structure, rates of evolution, developmental function, and the degree of functional redundancy, the MADS-box transcription factor family can be divided into two types of MADS-box proteins; Type I and Type II, which contain three additional sequence domains and differ in their DNA binding properties compared to Type I1
Sequence comparisons indicate that ZmMADS1a codes for a putative Type II MIKCC transcription factor
Phylogenetic analysis indicates that ZmMADS1a is closely related to ZAG2, ZmMADS1 and other proteins that function in the regulation of flower and seed development (Fig. 1III)

Summary

Introduction

Rates of evolution, developmental function, and the degree of functional redundancy, the MADS-box transcription factor family can be divided into two types of MADS-box proteins; Type I (the SRF superfamily) and Type II (the MEF2 superfamily), which contain three additional sequence domains and differ in their DNA binding properties compared to Type I1. Functional studies in maize and rice have shown that Type II MADS-box genes play important roles in the processes of grain formation and flower development. Expression of some MIKCC-group genes from rice, tomato, and A. thaliana, among others, is affected by stress treatment, indicating that they are involved in regulating flowering time in response to stress[22]. ZAG3 is expressed in the inflorescence and can affect the growth of the meristem in maize[13] These genes are especially prominent on almost all levels of the gene regulatory network that controls reproductive development in flowering plants, but seed growth regulation has not been extensively studied. We identified and characterized the ZmMAD1a gene, which encodes a MADS-box transcription factor. Our study will clarify the mechanism underlying the molecular regulation of starch synthesis by ZmMAD1a, and will lay the foundation for further analyses of the starch metabolic pathways in maize

Methods

Results

Conclusion