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.

中文翻译：

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玉米不透明突变体不再如此不透明。

被子植物的胚乳是合子的种子器官，可储存营养储备以支持胚胎发生和种子发芽。谷物胚乳也是人类卡路里和工业原料的主要来源。玉米不透明胚乳突变体通常表现出不透明，面粉状的籽粒，以及其他异常种子和/或非种子表型。不透明的胚乳表型有时伴随着柔软的籽粒质地和增加的营养品质，包括更高的赖氨酸含量，这是引起玉米育种者注意的有价值的农艺性状。最近，越来越多的不透明基础基因已经克隆了突变体，并且基于不透明胚乳表型的分子基础，它们的表征已经开始阐明。这些突变体通过破坏编码玉米醇溶蛋白或非玉米醇溶蛋白的基因（位于蛋白质体中），参与胚乳代谢过程的酶或与胚乳贮藏程序相关的转录调节蛋白的基因进行分类。