phot1/NPH3信號系統(tǒng)在黑暗（A）和光照（B）條件下對PIN2內(nèi)膜循環(huán)兩條支路間平衡的調(diào)控機(jī)制
近日,，植物學(xué)領(lǐng)域國際學(xué)術(shù)期刊The Plant Cell在線刊登了中科院植物研究所研究人員的最新研究成果“The Signal Transducer NPH3 Integrates the Phototropin1 Photosensor with PIN2-Based Polar Auxin Transport in Arabidopsis Root Phototropism”,，研究者在文章中揭示了植物感知光信號并調(diào)控生長素極性運輸?shù)臋C(jī)制。
向光素1（phototropin1,，phot1）是一種極性地分布在細(xì)胞膜上的植物藍(lán)光信號受體,，NPH3是其關(guān)鍵的信號轉(zhuǎn)導(dǎo)蛋白。它們介導(dǎo)了植物的正（負(fù)）向光性彎曲等多種重要的生理反應(yīng),。PIN2是擬南芥根尖生長素極性運輸?shù)年P(guān)鍵蛋白,。然而，關(guān)于光信號對PIN2蛋白在內(nèi)膜循環(huán)的調(diào)控方式以及對生長素極性運輸?shù)挠绊?，尚缺乏直接證據(jù),。
中科院植物研究所林金星研究組和德國波恩大學(xué)František Baluška博士合作，通過分子細(xì)胞學(xué)的手段發(fā)現(xiàn)：不同的光照條件能調(diào)控PIN2蛋白進(jìn)入2條不同的內(nèi)膜運輸支路，一是指向植物液泡的蛋白質(zhì)降解支路,，二是指向細(xì)胞質(zhì)膜的“膜-泡”循環(huán)支路,。phot1能接受藍(lán)光信號，并通過信號傳遞蛋白NPH3來調(diào)控PIN2蛋白在這兩條支路間的平衡,。當(dāng)根尖定位的phot1接收到藍(lán)光信號后，NPH3依賴的信號支路被激活,，并促使位于液泡樣區(qū)室（VLC）中的PIN2進(jìn)入“膜-泡”循環(huán)支路,，于是PIN2的極性定位增強(qiáng)，生長素極性運輸速率也顯著提高,。當(dāng)根尖細(xì)胞處于黑暗條件時,，NPH3依賴的信號支路被關(guān)閉，更多的PIN2被儲存于液泡樣區(qū)室中,，相應(yīng)的生長素運輸速率也隨之降低,。該項研究中，他們還利用了非損傷微測技術(shù),，定量測定了phot1和NPH3在藍(lán)光照射下對生長素極性運輸?shù)挠绊憽?/p>
上述研究結(jié)果揭示了植物藍(lán)光受體phot1及其信號轉(zhuǎn)導(dǎo)蛋白NPH3是如何通過調(diào)控PIN2的細(xì)胞極性,，來控制根尖的生長素極性運輸，以及如何調(diào)控根尖負(fù)向光性生長的分子機(jī)制,，填補(bǔ)了根尖負(fù)向光性生長機(jī)制研究的空白,。
該研究得到了科技部、國家自然科學(xué)基金委員會,、中科院和中國博士后科學(xué)基金的支持,。（生物谷Bioon.com）
doi:10.1105/tpc.111.094284
PMC:
PMID:
The Signal Transducer NPH3 Integrates the Phototropin1 Photosensor with PIN2-Based Polar Auxin Transport in Arabidopsis Root Phototropism
Yinglang Wana, Jan Jasikb,c,1, Li Wanga, Huaiqing Haoa, Dieter Volkmannb, Diedrik Menzelb, Stefano Mancusod, František Baluškab,e,1 and Jinxing Lina,1,2
Under blue light (BL) illumination, Arabidopsis thaliana roots grow away from the light source, showing a negative phototropic response. However, the mechanism of root phototropism is still unclear. Using a noninvasive microelectrode system, we showed that the BL sensor phototropin1 (phot1), the signal transducer NONPHOTOTROPIC HYPOCOTYL3 (NPH3), and the auxin efflux transporter PIN2 were essential for BL-induced auxin flux in the root apex transition zone. We also found that PIN2-green fluorescent protein (GFP) localized to vacuole-like compartments (VLCs) in dark-grown root epidermal and cortical cells, and phot1/NPH3 mediated a BL-initiated pathway that caused PIN2 redistribution to the plasma membrane. When dark-grown roots were exposed to brefeldin A (BFA), PIN2-GFP remained in VLCs in darkness, and BL caused PIN2-GFP disappearance from VLCs and induced PIN2-GFP-FM4-64 colocalization within enlarged compartments. In the nph3 mutant, both dark and BL BFA treatments caused the disappearance of PIN2-GFP from VLCs. However, in the phot1 mutant, PIN2-GFP remained within VLCs under both dark and BL BFA treatments, suggesting that phot1 and NPH3 play different roles in PIN2 localization. In conclusion, BL-induced root phototropism is based on the phot1/NPH3 signaling pathway, which stimulates the shootward auxin flux by modifying the subcellular targeting of PIN2 in the root apex transition zone.
