ZmDof3, a maize endosperm-specific Dof protein gene, regulates starch accumulation and aleurone development in maize endosperm

Abstract

To explore the function of Dof transcription factors during kernel development in maize, we first identified Dof genes in the maize genome. We found that ZmDof3 was exclusively expressed in the endosperm of maize kernel and had the features of a Dof transcription factor. Suppression of ZmDof3 resulted in a defective kernel phenotype with reduced starch content and a partially patchy aleurone layer. The expression levels of starch synthesis-related genes and aleurone differentiation-associated genes were down-regulated in ZmDof3 knockdown kernels, indicating that ZmDof3 plays an important role in maize endosperm development. The maize endosperm, occupying a large proportion of the kernel, plays an important role in seed development and germination. Current knowledge regarding the regulation of endosperm development is limited. Dof proteins, a family of plant-specific transcription factors, play critical roles in diverse biological processes. In this study, an endosperm-specific Dof protein gene, ZmDof3, was identified in maize through genome-wide screening. Suppression of ZmDof3 resulted in a defective kernel phenotype. The endosperm of ZmDof3 knockdown kernels was loosely packed with irregular starch granules observed by electronic microscope. Through genome-wide expression profiling, we found that down-regulated genes were enriched in GO terms related to carbohydrate metabolism. Moreover, ZmDof3 could bind to the Dof core element in the promoter of starch biosynthesis genes Du1 and Su2 in vitro and in vivo. In addition, the aleurone at local position in mature ZmDof3 knockdown kernels varied from one to three layers, which consisted of smaller and irregular cells. Further analyses showed that knockdown of ZmDof3 reduced the expression of Nkd1, which is involved in aleurone cell differentiation, and that ZmDof3 could bind to the Dof core element in the Nkd1 promoter. Our study reveals that ZmDof3 functions in maize endosperm development as a positive regulator in the signaling system controlling starch accumulation and aleurone development.

OPAQUE11 Is a Central Hub of the Regulatory Network for Maize Endosperm Development and Nutrient Metabolism

“…Gontarek et al (2016) maturation and is also a repressor of germination-specific genes (McCarty et 77 al., 1991;Hoecker et al, 1995). Another maize endosperm-specific DOF TF,78 ZmDof3, is reportedly a direct activator of NKDs and a key regulator in starch 79 accumulation and endosperm development (Qi et al, 2017). Thus, the 80 identification and functional analysis of key TFs are important for 81 understanding the mechanisms of endosperm development.…”

ZmDof30 Negatively Regulates the Promoter Activity of the Pollen-Specific Gene Zm908

“…PBF (prolamin-box binding factor) and ZmDof3 , both of which are members of the Dof transcription factor family in maize, were reported to play critical roles in seed development (Marzabal et al, 2008; Qi et al, 2016). PBF is predominantly expressed in embryos, endosperm and seeds, and it positively regulates expression of the zein gene in developing maize seed (Marzabal et al, 2008).…”

“…These regions function in transcriptional regulation, mediating activation or repression of gene expression by interacting with other regulatory proteins, and are likely to contribute to the diverse functions of Dof transcription factors. The Dof members identified thus far participate in the regulation of genes involved in diverse physiological processes, such as plant hormone responses (Kisu et al, 1997; Baumann et al, 1999; Mena et al, 2002), photosynthesis (Yanagisawa, 2000; Gupta et al, 2014), stress responses (Cai et al, 2016), seed germination (Santopolo et al, 2015), stomatal maturation and functioning (Negi et al, 2013), endosperm development (Vicente-Carbajosa et al, 1997; Marzabal et al, 2008; Qi et al, 2016) and pollen development (Chen et al, 2012). …”

Maize opaque mutants are no longer so opaque

“…NKD1 and NKD2 also can directly activate O2 itself (Gontarek et al 2016). Furthermore, NKD1 expression can be directly activated by DOF3 (Qi et al 2017). Interestingly, both the nkd mutants and RNAi lines of DOF3 ( Dof3RNAi ) exhibit defects in SE and AL cell differentiation (Gontarek et al 2016; Qi et al 2017; Yi et al 2015).…”

“…Furthermore, NKD1 expression can be directly activated by DOF3 (Qi et al 2017). Interestingly, both the nkd mutants and RNAi lines of DOF3 ( Dof3RNAi ) exhibit defects in SE and AL cell differentiation (Gontarek et al 2016; Qi et al 2017; Yi et al 2015). NKD genes, DOF3 , PBF , and O2 , have recently been identified as direct targets of O11, which is a bHLH family TF encoded by a gene expressed specifically in the endosperm (Fig.…”