Department of Botany, Oklahoma State University, Stillwater, Oklahoma, United States of America.
PLoS One. 2011;6(12):e28398. doi: 10.1371/journal.pone.0028398. Epub 2011 Dec 2.
The SeedGenes database (www.seedgenes.org) contains information on more than 400 genes required for embryo development in Arabidopsis. Many of these EMBRYO-DEFECTIVE (EMB) genes encode proteins with an essential function required throughout the life cycle. This raises a fundamental question. Why does elimination of an essential gene in Arabidopsis often result in embryo lethality rather than gametophyte lethality? In other words, how do mutant (emb) gametophytes survive and participate in fertilization when an essential cellular function is disrupted? Furthermore, why do some mutant embryos proceed further in development than others? To address these questions, we first established a curated dataset of genes required for gametophyte development in Arabidopsis based on information extracted from the literature. This provided a basis for comparison with EMB genes obtained from the SeedGenes dataset. We also identified genes that exhibited both embryo and gametophyte defects when disrupted by a loss-of-function mutation. We then evaluated the relationship between mutant phenotype, gene redundancy, mutant allele strength, gene expression pattern, protein function, and intracellular protein localization to determine what factors influence the phenotypes of lethal mutants in Arabidopsis. After removing cases where continued development potentially resulted from gene redundancy or residual function of a weak mutant allele, we identified numerous examples of viable mutant (emb) gametophytes that required further explanation. We propose that the presence of gene products derived from transcription in diploid (heterozygous) sporocytes often enables mutant gametophytes to survive the loss of an essential gene in Arabidopsis. Whether gene disruption results in embryo or gametophyte lethality therefore depends in part on the ability of residual, parental gene products to support gametophyte development. We also highlight here 70 preglobular embryo mutants with a zygotic pattern of inheritance, which provide valuable insights into the maternal-to-zygotic transition in Arabidopsis and the timing of paternal gene activation during embryo development.
SeedGenes 数据库（www.seedgenes.org）包含了 400 多个在拟南芥胚胎发育中起作用的基因的信息。这些 EMBRYO-DEFECTIVE（EMB）基因中的许多基因编码的蛋白质在整个生命周期中都具有必需的功能。这就提出了一个基本问题。为什么在拟南芥中消除一个必需基因通常会导致胚胎致死，而不是配子体致死？换句话说，当一个必需的细胞功能被破坏时，突变（emb）配子体如何生存并参与受精？此外，为什么有些突变胚胎比其他胚胎发育得更远？为了解决这些问题，我们首先根据文献中提取的信息，建立了一个拟南芥配子体发育所必需基因的已审定数据集。这为与从 SeedGenes 数据集中获得的 EMB 基因进行比较提供了基础。我们还鉴定了那些在功能丧失突变中表现出胚胎和配子体缺陷的基因。然后，我们评估了突变表型、基因冗余、突变等位基因强度、基因表达模式、蛋白质功能和细胞内蛋白质定位之间的关系，以确定哪些因素影响拟南芥致死突变体的表型。在去除了由于基因冗余或弱突变等位基因的残余功能而可能导致继续发育的情况后，我们鉴定了许多有活力的突变（emb）配子体的例子，这需要进一步解释。我们提出，来自二倍体（杂合子）孢母细胞中转录产生的基因产物的存在，常常使突变配子体能够在拟南芥中生存必需基因的缺失。因此，基因的破坏是否导致胚胎或配子体致死，部分取决于残留的、亲本基因产物支持配子体发育的能力。我们还在这里强调了 70 个具有合子遗传模式的原球形胚胎突变体，这些突变体为拟南芥中母本到合子的转变以及胚胎发育过程中父本基因激活的时间提供了有价值的见解。
