探討番茄的CEP2/3胜肽參與叢枝菌根菌促進側根形成之作用

植物的側根經常會在與叢枝菌根菌( arbuscular mycorrhizal fungi)共生的時候增加。在我們過去的研究中已經發現，菌根菌共生會使番茄中的C-terminally encoded peptides (CEPs)，SlCEP2，表現量下降。外源施用於根部的生長素會減輕由脯胺酸上具有羥基化修飾的CEP2 (CEP2Hyp)胜肽處理所造成的側根形成缺陷，顯示CEP2會通過影響根部生長素相關的路徑來負調控側根形成。SlCEPR1 (CEP receptor 1)可能為CEP2的受體。同樣的，菌根菌共生可能會減輕CEP2胜肽的負面影響來增加側根形成。本研究的主旨在於更進一步探討CEP2、CEPR1以及另一個也會被菌根菌共生負調節的CEP3，在菌根菌共生促進的側根生長中的作用。本研究發現CEP2的表現會可能受到由菌根菌所提供的氮源影響。成熟CEP2胜肽表現在細胞核、細胞質與細胞膜，並且CEP2胜肽可能並不會被運輸到植物的地上部。菌根菌共生與CEP2Hyp胜肽在側根原基形成上具有相反的功能。在根部施用IAA可以減輕CEP2Hyp所造成的側根形成缺陷。相反的，在地上部施用NAA卻不能恢復因CEP2Hyp處理而下降的植物側根密度，表示CEP2Hyp胜肽主要影響是在側根發育扮演重要角色且是來自根部的生長素。與病毒誘導的CEP2基因靜默 (CEP2-VIGS) 植物相反，CEPR1-VIGS植物的側根密度仍會被菌根菌共生誘導增加，顯示CEP2的基因表現量對菌根菌共生促進的側根形成可能更為重要。大量表現CEP3會抑制菌根菌增加側根形成的能力，雖然其確切機制仍然未知。在我們的系統中，CEP2、CEPR1和CEP3對於菌根菌的生長發育非常微弱或無明顯影響。這些結果有助於了解菌根菌共生是如何通過調節CEP胜肽來增進番茄側根形成。

關鍵字

叢枝菌根菌；胜肽荷爾蒙；胜肽受體；側根形成；生長素

並列摘要

Plants often have increased lateral root (LR) formation under symbiosis with arbuscular mycorrhizal (AM) fungi. In previous study, we found that SlCEP2, one tomato C-terminally encoded peptide (CEP), was downregulated by AM symbiosis. The defective of lateral root formation under synthetic CEP2 peptide with hydroxylation proline (CEP2Hyp) peptide treatment was mitigated by application of auxin on root, suggesting that CEP2 might negatively regulate LR formation through affecting auxin-related pathway in roots. SlCEPR1 (CEP receptor 1) may be the receptor of CEP2 peptide. Also, AM symbiosis may enhance LR formation through mitigating the negative effect of CEP2 peptide. The aim of this study is to further investigate the role of CEP2, CEPR1 and another AM-repressed CEP3 in AM-induced LR formation. This study found that the expression of CEP2 might be influenced by nitrogen supply from AM fungi. The subcellular localization of mature CEP2 peptide is at nucleus, cytoplasm and plasma membrane, and CEP2 peptide may not be transported to shoot. AM symbiosis and CEP2Hyp peptide had a contrary effect on the formation of unemerged lateral root primordia (LRP). Applying IAA on tomato root could mitigate the CEP2Hyp- affected LR defect. In contrast, application of NAA on the shoot apex did not recover LR density of CEP2Hyp- treated plants, suggesting that CEP2Hyp peptide mainly influence root-derived auxin essential for LR formation. Contrary to CEP2-VIGS (virus-induced gene silencing) plants, the LR density of CEPR1-VIGS plants were still increased by AM fungi inoculation, implying that the expression of CEP2 might be more crucial for AM-enhanced LR formation. Overexpressing CEP3 impacted AM-induced LR formation although the clear mechanism is still unknown. In our system, the influence of CEP2, CEPR1 and CEP3 on AM fungal development was very subtle or no significant influence. These results could help us to clarify how AM symbiosis enhance tomato LR formation through CEP peptide.

並列關鍵字

arbuscular mycorrhizal symbiosis ； C-terminally encoded peptide (CEP) ； lateral root formation ； peptide hormone ； auxin

參考文獻

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探討番茄的CEP2/3胜肽參與叢枝菌根菌促進側根形成之作用

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