SummaryCell fate determination and primordium initiation on the placental surface are two key events for ovule formation in seed plants, which directly affect ovule density and seed yield. Despite ovules form in the marginal meristematic tissues of the carpels, angiosperm carpels evolved after the ovules. It is not clear how the development of the ovules and carpels is coordinated in angiosperms. In this study, we identify the S. lycopersicum CRABS CLAW (CRC) homologue SlCRCa as an essential determinant of ovule fate. We find that SlCRCa is not only expressed in the placental surface and ovule primordia but also functions as a D‐class gene to block carpel fate and promote ovule fate in the placental surface. Loss of function of SlCRCa causes homeotic transformation of the ovules to carpels. In addition, we find low levels of the S. lycopersicum AINTEGUMENTA (ANT) homologue (SlANT2) favour the ovule initiation, whereas high levels of SlANT2 promote placental carpelization. SlCRCa forms heterodimer with tomato INNER NO OUTER (INO) and AGAMOUS (AG) orthologues, SlINO and TOMATO AGAMOUS1 (TAG1), to repress SlANT2 expression during the ovule initiation. Our study confirms that angiosperm basal ovule cells indeed retain certain carpel properties and provides mechanistic insights into the ovule initiation.

中文翻译：

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SlCRCa 是控制番茄胚珠命运决定的关键 D 类基因

摘要细胞命运决定和胎盘表面原基起始是种子植物胚珠形成的两个关键事件，直接影响胚珠密度和种子产量。尽管胚珠是在心皮的边缘分生组织中形成的，但被子植物心皮是在胚珠之后进化的。目前尚不清楚被子植物中胚珠和心皮的发育是如何协调的。在这项研究中，我们确定了番茄蟹爪（CRC) 同系物结直肠癌作为胚珠命运的重要决定因素。我们发现结直肠癌不仅在胎盘表面和胚珠原基中表达，而且在胎盘表面作为D类基因阻断心皮命运并促进胚珠命运。丧失功能结直肠癌导致胚珠同源异型转化为心皮。此外，我们发现低水平番茄番茄（蚂蚁) 同系物 (斯兰特2）有利于胚珠的形成，而高水平的斯兰特2促进胎盘心皮化。 SlCRCa 与番茄 INNER NO OUTER (INO) 和 AGAMOUS (AG) 直系同源物 SlINO 和 TOMATO AGAMOUS1 (TAG1) 形成异二聚体，以抑制斯兰特2胚珠起始期间的表达。我们的研究证实，被子植物基底胚珠细胞确实保留了某些心皮特性，并为胚珠的形成提供了机制见解。