Maize opaque mutants are no longer so opaque

Abstract

The endosperm of angiosperms is a zygotic seed organ that stores nutrient reserves to support embryogenesis and seed germination. Cereal endosperm is also a major source of human calories and an industrial feedstock. Maize opaque endosperm mutants commonly exhibit opaque, floury kernels, along with other abnormal seed and/or non-seed phenotypes. The opaque endosperm phenotype is sometimes accompanied by a soft kernel texture and increased nutritional quality, including a higher lysine content, which are valuable agronomic traits that have drawn attention of maize breeders. Recently, an increasing number of genes that underlie opaque mutants have been cloned, and their characterization has begun to shed light on the molecular basis of the opaque endosperm phenotype. These mutants are categorized by disruption of genes encoding zein or non-zein proteins localized to protein bodies, enzymes involved in endosperm metabolic processes, or transcriptional regulatory proteins associated with endosperm storage programs.

European maize genomes unveil pan-genomic dynamics of repeats and genes

“…We also detected a number of genes that function in the establishment and regulation of prolamin content and structure of the maize endosperm ( Figure 5B). These genes encode the direct transcriptional regulator ohp1 of  and  zeins and several genes regulating the packaging of zeins and starch granules: opaque endosperm o7 and o10, empty pericarp 16, floury endosperm fl1 and naked endosperm nkd1 [44][45][46][47].…”

OS1 functions in the allocation of nutrients between the endosperm and embryo in maize seeds

“…Changes in nutrient composition are key causes for endosperm opacity (Zhang et al ). We therefore compared the compositions of zein and non‐zein proteins between mature seeds from os1 and Mo17.…”

“…Opaque and floury endosperm mutations affect the appearance of the endosperm, often by affecting accumulation of zeins, the major endosperm storage proteins. The corresponding genes have been cloned and functionally analyzed for many of these mutations, including o1 , o2 , o5 , o7 , o10 , o11 , fl1 , fl2 , fl3 , fl4 , nkd1 and nkd2 (Zhang et al ). O2 encodes a basic‐domain‐leucine‐zipper (bZIP) transcription factor (Schmidt et al ; Schmidt et al ).…”

Isoform sequencing provides insight into natural genetic diversity in maize

“…All InDel markers were confirmed by PCR and agarose gel electrophoresis, leading to 123 (58.8%) being effective (Figure 1d bottom). To further provide the reference sequences and to understand the formation of the vitreous endosperm in W64A, we surveyed the genes associated with endosperm texture based on previous studies (Zhang et al, 2018). We found similar copy numbers of opaque-associated genes, including zein, non-zein, enzyme and transcription factor genes, where they presented an average sequence diversity of 3.92% with a highest number of 26.9% (Figure 1e).…”