There are many different interactions existing between microorganisms and plants. Microorganisms are distinguished into pathogen and probiotics based on their behaviors with the host plant. The plant diseases are caused by pathogens, whereas probiotics trigger the plant defense and help the plant growth. One of the research interests in our lab is to study and reveal the mechanisms of interaction between pathogen/probiotics and plants. To address this research interest, the various approaches, such as big-data of bioinformatics, microbiology, biotechnology, and molecular biology, are being used. These findings provide novel information and knowledge for our lab as well as to the world, helping us to create innovative ideas like designing a new drug for plant diseases or novel biologics for promoting plant growth and defense responses.
微生物與植物之間有各種不同的相互作用。根據微生物對宿主植物的行為,其可被稱為病原或益生原。病原導致植物病害而益生原觸動植物防疫機制並促進植物生長。我們實驗室其中的研究興趣是探討病原/益生原與植物之間的相互作用。為了深入研究這個領域,我們利用了生物資訊的大數據、微生物學、生物科技及分子生物學等領域。這些研究發現對我們實驗室及世界都提供了新的資訊及知識,提供我們創新的想法,像是研發植物病害的新藥物或者製造新型生物製劑來促進植物生長及防禦反應。
In our lab, we developed a ContigViews system that can help researchers to analyze next-generation sequencing (NGS) data and understand the mechanism of plant’s disease or defense through data mining. For example, bolting at high temperature in Lettuce (Lactuca sativa) is a big problem in the market. To understand the mechanism of heat-induced bolting in Lettuce, we performed transcriptomic analysis in ContigViews system (Fig.1). Through data mining, we found that Cyclic nucleotide-gated ion channels 4 (CNGC4) might play an important role in the heat-induced bolting.
We also investigate the regulatory role of small RNAs (sRNAs) in Arabidopsis thaliana, Solanum lycopersicum. Micro RNA (miRNA) and short interfering RNA (siRNA), which are 18 to 25 nucleotides (nt) non-coding RNAs, play important roles in controlling the gene expression of target mRNA in plants. In order to understand the overall regulatory networks of miRNA and siRNA, NGS is used. First, small RNA sequencing was performed to identify new microRNA (miRNA) and short interfering RNA (siRNA). Second, complementory base-pairing of small RNAs was performed by computer programming to predict potential target genes. Third, the predicted results were confirmed by degradome sequencing. These analyzed results will help scientists understand more about the regulatory networks of small RNAs in plants.
我們實驗室團隊研發了ContigViews 軟體。此軟體可協助研究人員分析次世代定序 (NGS) 及進行資料探勘,進而了解植物的疾病與防禦機制。例如,萵苣 (Lactuca sativa) 在高溫下抽苔是市場上的一個大問題。為了理解萵苣熱誘導抽苔的機制,我們透過 ContigViews 軟體進行轉錄組分析(圖1)。透過資料探勘,我們發現 Cyclic nucleotide-gated ion channels 4 (CNGC4) 可能在熱誘導抽苔中扮演了重要的角色。
我們也研究了小核糖核酸 (sRNAs) 在阿拉伯芥 (Arabidopsis thaliana, Solanum lycopersicum) 的調控角色。微核糖核酸 (miRNA) 和小干擾核糖核酸 (siRNA) 都是長18-25個核甘酸的非編碼核糖核酸,並且在控制植物目標 mRNA 的基因表現扮演重要的角色。我們透過 NGS,深入了解 miRNA 及 siRNA 的調控系統。首先,小片段的 RNA 序列用來辨認新的 miRNA 及 siRNA。第二,小 RNAs 的互補鹼基配對透過電腦程式來預測潛在的目標基因。第三,利用降解體定序來證實預測的結果。這些分析出來結果可以幫助科學家更加理解小 RNAs 在植物中的調控系統。
To understand the function of P1 and HC-Pro of potyvirus in PTGS suppression. We generated many plasmids containing P1, HC-Pro and P1/HC genes of TuMV, ZYMV and TEV (Fig. A) and transgenic plants (Fig. B). The HC-Pro and P1/HC-Pro expression in plants induce serrated leaf phenotypes, but the P1/HCTu plant phenotype were stronger than HCTu plant, indicating HC-Pro alone have the ability to suppress plant PTGS and when P1 together with HC-Pro expresses in a plants can show enhanced HC-Pro-mediated PTGS suppression ability. In addition, we also found TuMV P1/HC-Pro specifically triggered AGO1 posttranslational degradation (Fig. C), but not in AGO2 (Fig. D). In the IP profiles, showed P1 proteins from TuMV, ZYMV and TEV viruses all can interact with VERNALIZATION INDEPENDENCE 3/ SUPERKILLER8 (VIP3/SKI8) protein. These findings can further understand how viral suppressor interfere plant gene silencing mechanism.
為了探討馬鈴薯Y病毒 (Potyvirus) 在 PTGS 抑制時,其 P1 及 HC-Pro 的功能。我們製造了許多質體,含有 P1,HC-Pro 及 P1/HC 基因的 TuMV, ZYMV, TEV (圖A) 及轉基因植物 (圖B)。植物中的 HC-Pro 和 P1/HC-Pro 表現會誘導葉子呈鋸齒狀,P1/HCTu 植物比 HCTu 植物的葉子呈更多鋸齒,這代表單單 HC-Pro 就有能力抑制植物PTGS,而 P1 及 HC-Pro 都在植物中表現顯示增強的 HC-Pro 介導 PTGS 的抑制能力。我們也發現 TuMV P1/HC-Pro 會專門誘發 AGO1 後轉譯降解 (圖C),AGO2 則不會 (圖D)。IP 位址顯示,來自TuMV, ZYMV 及TEV 病毒的 P1 蛋白質都與 VERNALIZATION INDEPENDENCE 3 / SUPERKILLLER 8 (VIP3/SKI8) 蛋白質相互作用。這些發現可用來更深入研究病毒抑制基因如何干擾植物基因靜默機制。
We investigated that how effectors of pathogens interfere gene silencing pathway. The PHYL1 effector of phytoplasma inhibits miR396 expression, resulting in mis-regulation of miR396 on the target mRNA SVP, which is an important negative flowering regulator. Mis-regulation on miR396-SVP mRNA causes leafy flower formation (Fig. 3). We thus created miR396 knockout plants through CRISPR/Cas9 method and miR396 overexpression transgenic Arabidopsis through T-DNA insertion to clarify whether miR396 could have impact on SVP expression level.
Besides, through bioinformatic prediction, we identified several potential proteins that interacted with PHYL1. In vivo immuno-precipitation experiments showed that IMP have physical interaction with PHYL1 among the candidates. However, no interaction was found during in vitro assay, implying other bridging proteins was involved in the interaction. Tracing back to the bioinformatic prediction, we considered some candidate proteins which might be the key connection of IMP and PHYL1 that it is still under investigation.
Meanwhile, we found that PHYL1 can interact with SEP3, the MADS transcription factor, to form a complex and caused MADS box degradation. We also found the amino acid sequence in a-helix of PHYL1 and SEP3_K were similar, implying their interaction (Fig. 4). Therefore, the interaction of SEP3_K and PHYL1 was examined by mutating the α-helix of PHYL1 and performing pull-down assays. The results showed that PHYL1 mutant did not interact with SEP3_K, proving that α-helix plays a critical role in PHYL1 and SEP3_K interaction.
我們探討病原的效應蛋白如何干擾基因靜默路徑。植物菌質體的 PHYL1 效應蛋白抑制 miR396 表現,導致 miR396 對於目標 mRNA SVP 調控失調,SVP 則是一個重要的負開花調控。miR396-SVP mRNA的失調導致葉化花形成 (圖3)。我們透過 CRISPR/Cas9 製造了剔除 miR396 基因的植物,也通過插入 T-DNA 使基轉阿拉伯芥 miR396 過度表現,確認 miR396 是否影響 SVP 表現程度。
此外,透過生物資訊的推測,我們已辨別幾個可能與 PHYL1 相互作用的蛋白質。活體免疫沉澱實驗顯示 IMP 蛋白與 PHYL1 有相互作用。但是,試管實驗並沒有顯示任何相互作用,這代表其他橋接蛋白也牽涉在這個作用中。再回推生物資訊的預測,我們發現並研究一些可能是 IMP 與 PHYL2 的橋接蛋白。另外,我們發現 PHYL1 會與 MADS 轉錄因子 SEP3 一起形成複合體並導致 MADS 盒子降解。我們也發現 PHYL1 與 SEP3_K 在α-螺旋有相似的氨基酸序列,圖4顯示他們的相互作用。因此,突變 PHYL1 的α-螺旋及進行拉下實驗可以檢驗 SEP3_K 與 PHYL1 之間的相互作用。實驗結果顯示突變的 PHYL1 沒有與 SEP3_K 互動,證明α-螺旋對 PHYL1 與 SEP3_K 之間的互動扮演重要的角色。
Marchantia polymorpha, also known as common liverwort, is the basal land plant lineage in a grade of bryophytes. This plant has been studied for more than 200 years to investigate plant evolution, life cycle, morphology and physiological responses. Now, it is considered as an excellent model plant because of the development of easy-to-use technical tools and with the establishment and release of genome sequences. To understand small RNA evolution in basal land plants, we identified MpMIR genes by comprehensive sequencing approaches and all of the information has been annotated in the genome database. In M. polymorpha, it is thought most of the miRNA species were novel and showed unique regulation, and only seven miRNA families have conserved targets in plants. We have cooperated with Laboratory of Plant Molecular Biology in Kyoto University for many years to perform CRISPR/Cas9 gene editing for genetic research (Fig. 5). We produced precise mutagenesis on MIRs and those core genes mediating RNA silencing pathway. Besides, we survey the MpAGO1-associated small RNA and try to figure out the characteristics of small RNA in M. polymorpha RISC complex. To better understand the roles of MpAGOs and two MpPIWI proteins on epigenetic regulation and phase transition, we also collected Mpago4, Mpago9, Mppiwia and Mppiwib mutants for further assay. We are happy to be in M. polymorpha research community and to share our findings to the worldwide.
Marchantia polymorpha 也就是地錢,屬於陸生植物中的地錢門。這個植物200多年前就被用來研究植物的演化、生命週期、型態及生理反應。如今,地錢是一個非常好的模式植物,其研究工具技術亦有一定發展及基因體序列也已完成。為了瞭解小核糖核酸在地錢門植物的演化,我們透過全面的定序識別了 MpMIR 基因,此基因的所有資料也已含在基因資料庫裡。M. polymorpha 大部分的 miRNA 都被認為是新種類且展示獨特的調控,只有7種 miRNA 家族在植物中有保守的目標。我們也與京都大學植物分子生物實驗室有多年的合作,利用 CRISPR/Cas9 進行基因編輯研究 (圖5)。我們製造出 MIRs 上準確的突變與調解 RNA 靜默途徑的主要基因。此外,我們調查有關 MpAGO1 的小核糖核酸並嘗試找出小核糖核酸在 M. polymorpha RISC 複合體的特質。為了更理解 MpAGOs 與兩個 MpPIWI 蛋白在表觀遺傳調控與轉變過程扮演的角色,我們收集了MpAGO4, MpAGO9, Mppiwia 及 Mppiwib 的突變來進行更多測試。我們非常高興可以在地錢的研究團隊中及向全球分享我們的發現。
1. Lin, S.S.*, Chen, Y., Lu, M.J.* (2019) Degradome Sequencing in Plants. In: de Folter S. (eds) Plant MicroRNAs. Methods Molecular Biology, vol 1932. pp197-213. Humana Press, New York, NY. (First & co-correspond author).