Nature本期封面所示为一个花粉管在一种新发现的化学引诱剂LURE1引诱下按“N-形”形状生长。
精确的花粉管引导是开花植物成功受精的关键。花粉管引诱剂的概念是十九世纪末提出的,当时人们发现花粉管朝介质上被切除的雌蕊组织的方向生长。2001年,助细胞(英文名synergid cell,其位置在卵细胞旁)被发现分泌一种可溶因子,该因子引导花粉管向胚囊生长。现在,这些花粉管引诱剂终于被识别出来了。助细胞是从名为“蓝猪儿”(Torenia fournieri)的植物中分离出来的,这种植物的独特之处是有一个突出的胚囊。所分泌的引导因子被发现是富含半胱氨酸的多肽,属于类似防卫素的蛋白,被命名为LUREs。(生物谷Bioon.com)
生物谷推荐原始出处:
Nature 458, 357-361 (19 March 2009) | doi:10.1038/nature07882
Defensin-like polypeptide LUREs are pollen tube attractants secreted from synergid cells
Satohiro Okuda1,7, Hiroki Tsutsui1,7, Keiko Shiina1, Stefanie Sprunck2, Hidenori Takeuchi1, Ryoko Yui1, Ryushiro D. Kasahara1, Yuki Hamamura1, Akane Mizukami1, Daichi Susaki1, Nao Kawano1, Takashi Sakakibara1, Shoko Namiki1, Kie Itoh3, Kurataka Otsuka4, Motomichi Matsuzaki4, Hisayoshi Nozaki4, Tsuneyoshi Kuroiwa5, Akihiko Nakano4,6, Masahiro M. Kanaoka1, Thomas Dresselhaus2, Narie Sasaki1,7 & Tetsuya Higashiyama1,7
1 Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
2 Cell Biology/Plant Physiology, University of Regensburg, Universit?tsstrae 31, 93053 Regensburg, Germany
3 Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan
4 Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
5 Research Information Center of Extremophile, Graduate School of Science, Rikkyo (Saint Paul's) University, Nishi-Ikebukuro, Tokyo 171-8501, Japan
6 Molecular Membrane Biology Laboratory, RIKEN Advanced Science Institute, Hirosawa, Wako, Saitama 351-0198, Japan
7 These authors contributed equally to this work.
8 Correspondence to: Tetsuya Higashiyama1,7 Correspondence and requests for materials should be addressed to T.H.
For more than 140 years, pollen tube guidance in flowering plants has been thought to be mediated by chemoattractants derived from target ovules1. However, there has been no convincing evidence of any particular molecule being the true attractant that actually controls the navigation of pollen tubes towards ovules. Emerging data indicate that two synergid cells on the side of the egg cell emit a diffusible, species-specific signal to attract the pollen tube at the last step of pollen tube guidance1, 2, 3. Here we report that secreted, cysteine-rich polypeptides (CRPs) in a subgroup of defensin-like proteins are attractants derived from the synergid cells. We isolated synergid cells of Torenia fournieri, a unique plant with a protruding embryo sac, to identify transcripts encoding secreted proteins as candidate molecules for the chemoattractant(s). We found two CRPs, abundantly and predominantly expressed in the synergid cell, which are secreted to the surface of the egg apparatus. Moreover, they showed activity in vitro to attract competent pollen tubes of their own species and were named as LUREs. Injection of morpholino antisense oligomers against the LUREs impaired pollen tube attraction, supporting the finding that LUREs are the attractants derived from the synergid cells of T. fournieri.