Arabidopsis HAP2 (GCS1) is a sperm-specific gene required for pollen tube guidance and fertilization
Arabidopsis HAP2 (GCS1) is a sperm-specific gene required for pollen tube guidance and fertilization
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DOI：
10.1242/dev.02683
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发表时间：
2006-12-01
期刊：
影响因子：
4.6
通讯作者：
Preuss, Daphne
中科院分区：
文献类型：
--
作者：
von Besser, Kiera;Frank, Aubrey C.;Preuss, Daphne
在开花植物中，精子细胞在花粉细胞质中发育并通过花粉运输。口腔组织通过花粉管向胚珠延伸，是高度极化的细胞延伸。在瞄准胚珠后，花粉管破裂，释放出两个精子，使一个卵子和一个中心细胞受精。在这里，我们鉴定了编码拟南芥HAP2的基因，证明它与GCS1等位。HAP2仅在单倍体精子中表达，是有效的花粉管引导到胚珠所必需的。我们发现了一个插入（hap2-1），它破坏了蛋白质的c端部分，并用β -葡糖醛酸酶报告基因标记突变花粉粒。通过监测报告基因的表达，我们发现hap2-1在离体和雌蕊中都不会缩短花粉管的长度，但它使胚珠的靶向性降低了两倍。此外，我们发现hap2精子被送到胚珠后不能开始受精。预计HAP2编码一种具有n端分泌信号、单跨膜结构域和c端富含组氨酸结构域的蛋白。这些结果表明HAP2具有双重作用，既在花粉管引导中起作用，又在受精中起作用。此外，我们的研究结果表明，长期以来被认为是被动货物的精子参与了将花粉管导向其目标的过程。
In flowering plants, sperm cells develop in the pollen cytoplasm and are transported through. oral tissues to an ovule by a pollen tube, a highly polarized cellular extension. After targeting an ovule, the pollen tube bursts, releasing two sperm that fertilize an egg and a central cell. Here, we identified the gene encoding Arabidopsis HAP2, demonstrating that it is allelic to GCS1. HAP2 is expressed only in the haploid sperm and is required for efficient pollen tube guidance to ovules. We identified an insertion (hap2-1) that disrupts the C-terminal portion of the protein and tags mutant pollen grains with the beta-glucuronidase reporter. By monitoring reporter expression, we showed that hap2-1 does not diminish pollen tube length in vitro or in the pistil, but it reduces ovule targeting by twofold. In addition, we show that the hap2 sperm that are delivered to ovules fail to initiate fertilization. HAP2 is predicted to encode a protein with an N-terminal secretion signal, a single transmembrane domain and a C-terminal histidine-rich domain. These results point to a dual role for HAP2, functioning in both pollen tube guidance and in fertilization. Moreover, our findings suggest that sperm, long considered to be passive cargo, are involved in directing the pollen tube to its target.