小麥赤黴病菌與番茄萎凋病菌之PSD2基因影響磷脂質組成、生長與產孢

"PSD2 gene affects phospholipid composition, growth and conidiation in Fusarium graminearum and F. oxysporum f. sp. lycopersici"

"許多種類之鐮孢菌具危害植物之能力，其中Fusarium graminearum（Fg）species complex之鐮孢菌可造成小麥赤黴病，其孢子可利用風傳播感染地上部之穗，並作為二次感染源在當季循環感染。Fg有性世代產生之子囊孢子與無性世代之分生孢子皆可做為感染源。番茄萎凋病菌F. oxysporum f. sp. lycopersici（Fol）曾於高雄的番茄田區造成三分之一以上之番茄受害。臺灣育成之番茄品種至今仍強調耐萎凋病之性狀，足見其重要性，然而臺灣目前針對鐮孢菌防治之推薦化學或生物農藥較少。磷脂質為構成生物個體細胞膜的主要成分，包含phosphatidylethanolamine（PE）、phosphatidylserine（PS）或phosphatidylcholine（PC）等不同種類。PE與其他磷脂質相比，較易增加膜的非雙層形成（nonbilayer-forming）特性，此特性在生物膜的分裂、融合、內嵌蛋白質的移動等時機扮演重要角色。酵素PS decarboxylase（Psd）參與真菌中，以PS為基質，經脫羧作用合成PE之過程。Psd2為酵素Psd的其中一種，本研究探討PSD2基因對Fg與Fol PE生合成、菌絲生長、孢子產生與毒力等功能之影響。在薄層層析試驗中可見Fg與Fol psd2突變株之PE生成量較野生株少。比較添加ethanolamine前後，突變株在微量元素培養基（minimal medium, MM）之生長情形，發現ethanolamine可恢復Fg與Fol psd2突變株之營養缺陷。Fg與Fol之psd2突變株在MM和PDA培養基之生長較野生株緩慢，而於大麥麥麩培養基則呈現相似之生長速率。在產孢方面，PSD2基因影響Fg分生孢子的型態，也影響Fol之分生孢子發芽率、厚膜孢子之產孢與其在菌絲上的著生形式。PSD2基因影響Fg胞外酵素分泌，但不影響Fg與Fol對小麥或番茄寄主之毒力。"

"Many members of the genus Fusarium can infect plants. Fusarium graminearum ( F g ) s p e c i e s c o m p l e x s u c h a s F. graminearum that can cause Fusarium head blight. Fg conidia can serve as secondary inoculum, spread by wing and infect plant parts above ground (e.g. head of wheat) repeatedly. Ascospores or conidia produced from sexual or asexual reproduction in Fg can both serve as inoculum. Fusarium oxysporum f. sp. lycopersici (Fol) used to cause damage up to one-third of tomato fields in 1982 in Kaohsiung, Taiwan. Many tomato cultivars bred in Taiwan emphasize the trait of resistance to Fusarium wilt. Currently, there are few recommended fungicides for controlling Fusarium infections in Taiwan. Phospholipids are main material of biological membranes, including phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylcholine (PC) and others. Compare to other kinds of phospholipids, PE can increase the nonbilayer-forming ability of membrane easily. This ability plays an important role in fusion and fission of membrane, and movement of embedded protein in membrane. Phosphatidylserine decarboxylase (Psd) including Psd2 takes part in PE formation of fungi. In this study, two independent Δpsd2 mutants each from F. graminearum PH-1 or F. oxysporum f. sp. lycopersici 4287 were constructed. The function of PSD2 on PE production, growth, production of conidia or chlamydospores, and virulence in the plant hosts were carefully examined. Comparing the strains grown in the absence or presence of ethanolamine (Etn) in minimal medium (MM), Δpsd2 mutants from either Fg or Fol exhibited Etn auxotrophy. Δpsd2 mutants of both Fg and Fol grew slower on MM and PDA media, while similar on barley bran media compared with their respective wild types. Meanwhile, PSD2 gene affected conidiation of Fg in addition to regulating the germination rate of conidia and formation of chlamydospores of Fol. Although PSD2 gene affected secretion of extracellular enzymes of Fg but not Fol, it is dispensable to virulence on wheat or tomato."