Hydatellaceae are water lilies with gymnospermous tendencies
Hydatellaceae are water lilies with gymnospermous tendencies
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DOI：
10.1038/nature06733
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发表时间：
2008-05-01
期刊：
影响因子：
64.8
通讯作者：
Friedman, William E.
中科院分区：
文献类型：
--
作者：
Friedman, William E.
开花植物Hydatellaceae最近被发现与古老的被子植物谱系睡莲（睡莲）有亲缘关系（1）。由于其关键的系统发育位置，Hydatellaceae的成员有可能提供被子植物起源和早期多样化的见解（2）。在这里，我报告说，Hydatella表达了几种罕见的胚胎学特征，在组合中，发现只有在成员的睡莲目。成熟时，雌配子体为四细胞、四核，并产生二倍体胚乳，这是大多数早期分歧被子植物谱系的特征（3，4）。与睡莲目的所有成员一样，黑藻属的胚乳发育最少，外胚乳是种子内主要的胚胎营养组织（5，6）。值得注意的是，黑藻表现出一种在有花植物中独特但为所有裸子植物所共有的母本种子供应策略（7）：受精前将营养物质分配给滋养胚的组织。这种特殊的情况下，受精前母体提供的种子在Hydatella很可能是一个单的的apomorphic功能Hydatellaceae的，但考虑到新发现的系统发育的位置，这个家庭，可能代表了一个plesiomorphic和过渡的条件与裸子植物的祖先开花植物的起源。
The flowering plant family Hydatellaceae was recently discovered to be allied to the ancient angiosperm lineage Nymphaeales ( water lilies)(1). Because of its critical phylogenetic position, members of the Hydatellaceae have the potential to provide insights into the origin and early diversification of angiosperms(2). Here I report that Hydatella expresses several rare embryological features that, in combination, are found only in members of the Nymphaeales. At maturity, the female gametophyte is four- celled, four- nucleate and will produce a diploid endosperm, as is characteristic of most early divergent angiosperm lineages(3,4). As with all members of the Nymphaeales, endosperm in Hydatella is minimally developed and perisperm is the major embryo- nourishing tissue within the seed(5,6). Remarkably, Hydatella exhibits a maternal seed-provisioning strategy that is unique among flowering plants, but common to all gymnosperms(7): pre- fertilization allocation of nutrients to the embryo- nourishing tissue. This exceptional case of pre- fertilization maternal provisioning of a seed in Hydatella may well be an apomorphic feature of Hydatellaceae alone but, given the newly discovered phylogenetic position of this family, potentially represents a plesiomorphic and transitional condition associated with the origin of flowering plants from gymnospermous ancestors.