Functional and evolutionary significance of the Bsister genes in flowering plants

B类花器官同一性基因（“B基因”）是同源异型的MADS盒基因，其在花发育过程中决定花瓣和雄蕊的同一性。Bsister（Bs）基因代表B基因的姐妹分支，从几种被子植物和裸子植物中分离得到，表明该MADS盒基因分支起源于3亿多年前。Bs基因在被子植物和裸子植物的雌性生殖器官中均有表达，在胚珠发育中起重要作用。然而，拟南芥Bs基因之一（abs/tt 16）的突变等位基因揭示只有轻微的表型影响种皮色素沉着和内皮发育。结合基因序列和表达水平的高度保守性，我们推测Bs基因在花发育中的作用比目前所认识的更为重要。为了验证这一假设，我们将分析可能的冗余与AGL 63，唯一的其他Bs基因在拟南芥基因组和B基因。通过对真双子叶植物加州罂粟和单子叶植物水稻的Bs基因的功能分析，我们将进一步了解Bs基因的进化意义。通过对三个代表性物种的分析，跨越了被子植物多样性的很大程度，我们的目标是了解Bs基因在被子植物进化过程中的功能动态。

Class B floral organ identity genes (‘B genes’) are homeotic MADS-box genes which specify petal and stamen identity during floral development. Bsister (Bs) genes are representing the putative sister clade of the B genes and were isolated from several angiosperms and gymnosperms indicating that this MADS-box gene clade originated more than 300 million years ago. Bs genes are predominantly expressed in female reproductive organs of both angiosperms and gymnosperms, suggesting an important role in ovule development. However, mutant alleles of one of the Arabidopsis Bs genes (abs/tt16) reveal only mild phenotypic effects in seed coat pigmentation and endothelium development. Taking together the high degree of conservation on both gene sequence and expression level we assume a more profound function of Bs genes in flower development than recognized so far. To test this hypothesis, we will analyze possible redundancies with AGL63, the only other Bs gene in the Arabidopsis genome and with the B genes. We will learn more about the evolutionary significance of Bs genes by functional analysis of Bs genes from the basal eudicot California poppy and from the monocot rice. Spanning a large degree of angiosperm diversity by analyzing three representative species we will aim at understanding the functional dynamics of Bs genes during angiosperm evolution.