Abstract
摘要:由細菌Ralstonia solanacearum (Rs) 引起之致死青枯病 (bacterial wilt,簡稱BW) 造成番茄等許多重要經濟作物的嚴重損失,而目前最有效的防治策略為抗病作物育種,故深入瞭解並善用作物天然抗病資源便至關重要。Hawaii 7996 (H7996) 為目前最穩定之青枯病抗病番茄品系,然其防禦機制與關鍵主導基因仍未明。本研究室已致力於茄科作物青枯病研究多年,針對H7996與其抗BW主控QTL Bwr12,目前已有以下突破性研究成果: (1) 全基因組序列分析結果發現H7996與感病品系Heinz1706在特定區域具高歧異度; (2)已建立高效之番茄葉與根pathogen-associated molecular patterns (PAMPs)-triggered immunity (PTI)反應分析系統,並指出H7996具強PTI與廣效抗病菌力; (3) Bwr12與H7996之PTI具強關連性,且位於Bwr12之receptor like kinases/proteins (RLKs/RLPs) 基因序列在 H7996與感病品系中具差異; (4)短暫基因靜默/過量表現與基因表現分析結果顯示Bwr12主導之BW抗性是由多個基因共同調控,其中12g520與12g550是BW抗性與PTI之關鍵正調控者,且12g520蛋白質產物可能座落在細胞膜,而12g690在BW抗性是負調控者且不參與PTI; (5)已培育出過量表現12g520或12g550之轉殖植物。 以上皆是首次報導之重要揭示,但箇中調控機制卻尚未解,故此三年計畫將針對上述三個抗病具關鍵RLK基因進行以下研究,以期深入闡明其機制與應用潛力: (I)分析在不同抗感病番茄品系中其序列歧異性與表現特性; (II)以轉殖植物深入探討其功能與特性; (III)以蛋白質體與轉錄體探討其具體調控機制; (IV)試驗基因標記(gene-based markers)以提高抗病育種之篩選精準度與效率。
Abstract: Bacterial wilt (BW) caused by Ralstonia solanacearum (Rs) is a deadly soil-borne vascular disease, leading to tremendous production losses of a wide range of economically important crops worldwide, including tomato. The most effective means for disease control is breeding for durable resistance. Exploring and using natural plant defense resources to develop efficient BW control strategies are therefore necessary but still very insufficient. Tomato cultivar Hawaii 7996 (H7996) is currently the most durable resistance source against bacterial wilt; however, the involved defense mechanism and crucial defense genes remain undetermined. We have been studying H7996 and its major BW-resistance QTL Bwr12 for many years and currently have accomplished the following: (1) Genome-wide sequence comparison analyses showed high sequence variations on several chromosomes between H7996 and the announced BW-susceptible cultivar Heniz 1706. (2) Using our newly established assay systems for pathogen-associated molecular patterns (PAMPs)-triggered immunity (PTI), we found that H7996 confers stronger PTI and tolerance to a wide range of pathogens. (3) Bwr12 correlates with stronger root PTI responses, and some of the Bwr12-associated receptor like kinases/proteins (RLKs/proteins) have significant sequence differences between H7996 and susceptible cultivars. (4) Results of transient gene silencing/overexpression and gene expression assays suggest that Bwr12-mediated BW-resistance involves multiple RLK/RLP genes. Furthermore, 12g520 and 12g550 are suggested to be positive regulators for BW-resistance and PTI, while 12g690 could be a negative regulator for BW-resistance and not involved in PTI. Moreover, 12g520 protein is probabaly localize on the plasma membrane. (5) Multiple independent transgenic tobacco lines containing CaMV35S::12g520/12g550-GFP have been generated. These noteworthy findings highlight the importance and novelty of H7996 defense nature and Bwr12; however, the involved regulatory mechanisms remained to be further elucidated. Building on the above bases, this three-year study aims to systematically decipher the involved regulatory mechanisms of three crucial RLK genes (12g520/12g550/12g690) and explore potential applications for disease control. To achieve this goal, the following specific aims will be pursued using the highly efficient functional genetic approaches and bioassay systems well-established in our group: (I) To further explore the sequence diversity and characteristics of these RLKs in H7996 and BW-susceptible cultivars; (II) To verify the functions of these RLKs in disease defense and their properties in transgenic plants. (III) To decipher the regulatory mechanisms underlying the functions of these RLKs by identifying their interactors and regulated targets; (IV) The reliability and efficiency of gene-based markers for high-precision selection will be evaluated.
Keyword(s)
番茄
初級免疫
PTI
青枯病
青枯病菌
QTL
RLK
tomato
innate immunity
PTI
bacterial wilt
Ralstonia solanacearum
QTL
RLK