李佳穎 胡利華 周海連 魏曉雙 王艷婷 王令強(qiáng)
摘要:果膠是植物細(xì)胞壁的主要組分,存在于胞間層與中間層,影響細(xì)胞的流變性與黏附性能。果膠的甲酯化程度影響果膠形態(tài),對(duì)穩(wěn)定細(xì)胞壁性質(zhì)以及植物生長發(fā)育過程具有重要作用。果膠甲酯酶(PME)是果膠去甲酯化修飾的關(guān)鍵酶類,果膠甲酯酶抑制子(PMEI)可特異地結(jié)合PME,調(diào)節(jié)其活性,共同決定果膠的去甲脂化。本文綜述了PME與PMEI的結(jié)構(gòu)及生化作用機(jī)制、相關(guān)基因家族和表達(dá)模式,并進(jìn)一步對(duì)二者介導(dǎo)的果膠去甲酯化過程對(duì)細(xì)胞壁的影響及其與花粉管發(fā)育、根器官形成等植物生長發(fā)育過程和逆境響應(yīng)關(guān)系的最新研究進(jìn)展做了介紹,并進(jìn)行了展望。
關(guān)鍵詞:果膠;果膠甲酯酶;果膠甲酯酶抑制子;細(xì)胞壁;逆境響應(yīng)
中圖分類號(hào):S188+.3文獻(xiàn)標(biāo)志碼: A
文章編號(hào):1002-1302(2021)08-0049-07
收稿日期:2020-07-27
基金項(xiàng)目:國家自然科學(xué)基金(編號(hào):31771775)。
作者簡介:李佳穎(1993—),女,河南開封人,博士研究生,主要從事果膠甲酯化修飾對(duì)細(xì)胞壁結(jié)構(gòu)影響研究。E-mail:jiayingli@webmail.hzau.edu.cn。
通信作者:王令強(qiáng),博士,教授,主要從事植物細(xì)胞壁合成調(diào)控機(jī)理研究。E-mail:lqwang@gxu.edu.cn。
果膠是由半乳糖醛酸(D-galacturonic acids,D-Gal-A)以α-1,4-糖苷鍵連接形成的酸性雜多糖[1],它可以改變細(xì)胞的流變性與黏附性能,對(duì)植物組織形態(tài)、器官建成、果實(shí)發(fā)育以及激素和逆境響應(yīng)等具有重要作用[2]。在工業(yè)中果膠也可作為食品添加劑、化妝品原料等被廣泛用于食品、醫(yī)療保健化學(xué)化工行業(yè)。
根據(jù)側(cè)鏈基團(tuán)不同,果膠主要分為同聚半乳糖醛酸聚糖(HG)、鼠李Ⅰ型半乳糖醛酸聚糖(RG-Ⅰ)和鼠李Ⅱ型半乳糖醛酸聚糖(RG-Ⅱ)。HG是由半乳糖醛酸共價(jià)連接的線性長鏈,RG-Ⅰ是由α-1,2-L-鼠李糖與α-1,4-D-半乳糖醛酸結(jié)合的聚合體,RG-Ⅱ的復(fù)雜多糖組成則包括D-半乳糖、L-半乳糖、L-鼠李糖和D-木糖等至少12種單糖,并通過硼酯鍵形成二聚體[3]。
除了單糖組成的差異外,果膠還受到各種修飾。在高爾基體合成的果膠高度甲酯化,通常在HG的C-6位高度甲酯化,O-2、O-3位部分乙?;痆1,4]。果膠的甲酯度可達(dá)70%,乙酰化程度為40%~85%,不同組織器官間存在差異。高爾基體合成的高甲酯化的果膠經(jīng)分泌小泡運(yùn)輸至細(xì)胞壁后,被果膠酶修飾,其中包括果膠甲酯酶(pectin methylesterases,PME)[3,5]。PME屬于碳水化合物酯酶CE8家族,是果膠發(fā)生水解反應(yīng)的第1個(gè)關(guān)鍵酶,目前發(fā)現(xiàn)和研究較多[6]。PME的活性可特異地被果膠甲酯酶抑制子(pectin methylesterases inhibitor,PMEI)調(diào)控。二者對(duì)于果膠的性質(zhì)、維持細(xì)胞形態(tài)及中間層的穩(wěn)定具有重要作用[7-8]。本研究綜述PME、PMEI的結(jié)構(gòu)和作用機(jī)制及其在植物生長發(fā)育中的作用。
1 PME和PMEI蛋白的結(jié)構(gòu)與生化作用機(jī)制
1.1 PME和PMEI的序列和結(jié)構(gòu)
根據(jù)N端有無PRO結(jié)構(gòu)域(PF04043),PME可分為Group Ⅰ 和Group Ⅱ 2類。Group Ⅰ(type Ⅱ)無PRO,分子量27~45ku。Group Ⅱ (type Ⅰ)有 1~3個(gè)PRO,分子量52~105 ku[2]。對(duì)來自微生物和植物的127個(gè)PME氨基酸序列比對(duì)后發(fā)現(xiàn),PME有5個(gè)特征序列片段(GxYxE、QAVAL、QDTL、DFIFG和LGRPW)[9]。
PME蛋白的三維結(jié)構(gòu)在細(xì)菌中首次被解析,此后在植物中也被闡明(圖1)[10-11]。番茄的PME為右旋β-螺旋蛋白,呈三股螺旋,其N端主要由一個(gè)α-螺旋與第1個(gè)β-折疊后的β-轉(zhuǎn)角構(gòu)成,C端由4個(gè)α-螺旋從與β-折疊側(cè)面平行的β-轉(zhuǎn)角處伸出,內(nèi)部芳香族氨基酸殘基形成較長的裂縫區(qū)域,為PME活性結(jié)合區(qū)域[12]?;钚越Y(jié)合區(qū)域內(nèi)的保守殘基預(yù)測為Phe80、Tyr135、Phe156、Tyr218、Trp223和Trp248,在植物中具保守性,在菊歐文式菌(Erwinia chrysanthemi)中Tyr135、Phe156、Trp223仍具保守性[11-12]。Dorokhov等也證明了天冬氨酸殘基(Asp136、Asp157)與谷氨酰胺殘基(Gln113、Gln135)在PME活性位點(diǎn)中的作用[13]。從三維(3D)模型看,植物的PME間活性位點(diǎn)殘基和序列相似度高,與細(xì)菌的PME有差異[2]。
按蛋白的基序分類,PMEI屬于隱馬爾科夫模型PF04043。typeⅠ型PME中的PRO結(jié)構(gòu)域與PMEI蛋白的序列具有相似性[7]。PMEI中保守性最強(qiáng)的為4個(gè)半胱氨酸殘基位點(diǎn),兩兩結(jié)合形成二硫鍵。獼猴桃PMEI的三維結(jié)構(gòu)中,4個(gè)α螺旋(α1、α2、α3、和α4)反向平行排列形成螺旋束,5個(gè)半胱氨酸殘基中前4個(gè)即Cys74、Cys114、Cys9和Cys18兩兩形成二硫鍵。其中,第1個(gè)二硫鍵與螺旋束內(nèi)部的疏水作用對(duì)蛋白結(jié)構(gòu)和穩(wěn)定性起到支撐作用,第2個(gè)二硫鍵連接αa與αb,αa、αb與αc分別是構(gòu)成N末端的3個(gè)短而彎曲的螺旋,與α1、α4構(gòu)成的平面平行并延伸至外側(cè),N末端所構(gòu)成的區(qū)域?qū)MEI蛋白結(jié)構(gòu)的穩(wěn)定性具有重要作用[14]。與PMEI均具有保守的半胱氨酸殘基不同的是,PME 除了部分植物外,真菌和細(xì)菌中均未發(fā)現(xiàn)有保守性半胱氨酸殘基[9]。
1.2 PME和底物的作用機(jī)制
PME的去甲脂化催化過程:PME中Asp225與Asp157二者以氫鍵結(jié)合,親核攻擊羧甲基酯鍵,與Phe160距離較近的Asp136充當(dāng)質(zhì)子供體,2個(gè)谷氨酰胺可以穩(wěn)定帶有負(fù)電荷的中間體,從而釋放甲醇,后Asp136與H2O中的質(zhì)子結(jié)合,致使催化底物與Asp157間氫鍵裂解,活性位點(diǎn)得以恢復(fù)(圖1)[11]。PME與底物形成多聚嵌合結(jié)構(gòu),有3種作用方式:(1)多鏈機(jī)制(multiple-chain mechanism)。在多條HG鏈上,PME催化底物去甲酯化后與底物解離,每次只有1個(gè)甲酯化的殘基被攻擊。(2)單鏈機(jī)制(single-chain mechanism)。在單條HG鏈上,PME將甲酯化的基團(tuán)連續(xù)去甲酯化。(3)多重攻擊機(jī)制(multiple-attack mechanism)。PME對(duì)底物中多個(gè)甲酯化基團(tuán)去甲酯化[15]。
PMEs的活性受溫度、pH值等植物所處內(nèi)外環(huán)境影響[16-17]。Denès等在蘋果中發(fā)現(xiàn),在pH值=7.0時(shí),PME的作用機(jī)制為單鏈多重攻擊機(jī)制,在pH值=4.5時(shí),則為多鏈多重攻擊機(jī)制[18]。Bonnin等用熒光標(biāo)記對(duì)PME的擴(kuò)散進(jìn)行追蹤發(fā)現(xiàn),纖維素存在的凝膠結(jié)構(gòu)中PME的擴(kuò)散更加明顯,且擴(kuò)散能力受到PME活性調(diào)控[19]。
type Ⅰ 型PME中的PRO也和PME活性調(diào)節(jié)有關(guān)。PRO與PMEI蛋白序列相似,可作為分子內(nèi)抑制子抑制PME活性,避免PME分泌至細(xì)胞壁前過早發(fā)揮去甲酯化作用;另外PRO還與PME在細(xì)胞壁上的錨定有關(guān)。研究表明,表達(dá)type Ⅰ型PME基因后,在生長發(fā)育前期可檢測到酸性PRO結(jié)構(gòu)域蛋白的活性,抑制PME活性防止果膠過早去甲酯化。而將PRO表達(dá)抑制后,PME活性積累增加,果膠的去甲酯化時(shí)期提前。再將PRO超表達(dá)后可恢復(fù)由于超表達(dá)PME引起的花粉管長度的改變[20-21]。
1.3 PMEI對(duì)PME的作用機(jī)制
PMEI主要結(jié)合PME的活性區(qū)域,與PME 以 1 ∶1 形成非共價(jià)可逆復(fù)合體(圖2)[12]。PMEI與PME中和底物結(jié)合有關(guān)殘基位點(diǎn)形成接觸面,使底物無法進(jìn)入PME活性區(qū)域。PME保守殘基位點(diǎn)Phe80、Tyr135和Trp223與底物間的相互作用同時(shí)受到阻礙。復(fù)合體的結(jié)合區(qū)域可形成較多氫鍵,提高其穩(wěn)定性。
PMEI和PME復(fù)合物的穩(wěn)定性受pH值影響。酸性條件下的解離常數(shù)低于中性條件下的10倍。當(dāng)處于接近生理pH值環(huán)境時(shí),PMEI與PME間的親和力最高。有趣的是,植物的PMEI對(duì)于真菌的PME抑制效果卻不大。獼猴桃PMEI蛋白對(duì)植物PME活性有抑制作用,但對(duì)細(xì)菌和真菌的PME無抑制作用[7,22-24]。原因包括:一是細(xì)菌PME的活性區(qū)域裂縫較深,PMEI無法深入覆蓋其活性區(qū)域;二是植物中的PME序列保守性較強(qiáng),而真菌中無類似的保守性位點(diǎn)[25-26]。
PMEs的活性受PMEI調(diào)控已有較多的分子生物學(xué)研究。在擬南芥種皮黏液釋放機(jī)制中,類枯草桿菌蛋白酶(subtilisin-like Ser protease,SBT)激活PMEI活性從而抑制PME活性[27]。轉(zhuǎn)錄因子LEUNIG_HOMOLOG/MUCILAGE MODIFIED1(LUH/MUM1)、SEEDSTICK(STK)與MYB52分別通過調(diào)控PMEI6、SBT1.7和PMEI14的表達(dá)而調(diào)控PME活性,影響種皮黏液釋放[28-30]。SBT3.5和PME17表達(dá)模式一致,SBT3.5可靶向結(jié)合type Ⅰ型PME的2個(gè)堿性基序位點(diǎn),對(duì)PME加工進(jìn)而將其釋放到胞質(zhì)中[27]。
PMEI可同時(shí)對(duì)多個(gè)PME產(chǎn)生抑制作用,具體互作模式仍需深入研究。水稻的PMEI12和PMEI8與小麥的TaPMEI對(duì)于外源性的PME活性都有抑制作用[31];棉花中的GhPMEI3對(duì)GhPME13和GhPME2均有抑制作用[32]。擬南芥的AtPMEI4與AtPMEI9和獼猴桃的PMEI可對(duì)柑橘和番茄的PME表現(xiàn)出活性抑制。植物的PMEI對(duì)植物PME有抑制作用,但對(duì)真菌PME無影響[28,33-34]。
2 PME和PMEI基因家族和表達(dá)模式
植物中PME是一類較大基因家族,在擬南芥(Arabidopsis thaliana)、水稻(Oryza sativa)、亞麻(Linum usitatissimum)、楊樹(Poplus trichocarpa)、番茄(Lycoperscicon esculentum)、梨(Pyrus bretschneideri)中已發(fā)現(xiàn)66、43、105、89、79、81個(gè)家族成員[35-37]。PMEI基因家族成員眾多,目前在擬南芥、高粱(Sorghum bicolor)、亞麻、短柄草(Brachypodium distachyon)、甘藍(lán)(Brassica oleracea)和蕓薹屬物種白菜(Brassica campestris ssp. chinensis)中鑒定的PMEI成員分別有79、54、55、95、38、95、100個(gè)[38-39]。
PME和PMEI家族成員具有特異表達(dá)模式,傾向于在幼嫩組織中表達(dá)。擬南芥的66個(gè)PME成員中,85%在花蕾發(fā)育期有表達(dá),表明PME可能參與花粉發(fā)育及花粉管伸長。PMEI基因與PME類似,在花粉中的表達(dá)最高,在花藥中表達(dá)數(shù)量最多[21]。部分PMEI基因存在組織特異表達(dá),且大多在花、花藥和幼根等幼嫩組織中表達(dá)。薺菜(Capsella rubella)與擬南芥等中的PMEI轉(zhuǎn)錄本數(shù)的比例相對(duì)較高,而與禾本科植物較低[35]。亞麻中有77.4%的PME在花蕾中有表達(dá),在成熟組織中分別有19個(gè)PME及24個(gè)PMEI表達(dá)。在水稻中也發(fā)現(xiàn)部分PMEI基因的組織表達(dá)特異性,如OsPMEI28和OsPMEI49分別在幼根和花中特異表達(dá)[33]。PME和PMEI存在互作表達(dá)模式,在亞麻早期纖維發(fā)育中PMEI表達(dá)數(shù)量最少,活性最弱,自次生細(xì)胞壁合成開始至停止沉積期間PMEI的活性較高,調(diào)控PME活性[35]。
逆境可誘導(dǎo)PME與PMEI的表達(dá)。在茉莉酸甲酯(MeJA)、水楊酸(SA)、脫落酸(ABA)、過氧化物、干旱、乙烯和冷害等脅迫下,PME與PMEI的表達(dá)均變化[32]。Chen等研究發(fā)現(xiàn),AtPMEI13與CbPMEI13受低溫誘導(dǎo),而受鹽脅迫和ABA處理抑制[40]。在水稻43個(gè)PME基因中,有27個(gè)在細(xì)胞伸長期如營養(yǎng)生長期以及幼莖中有較高表達(dá),且對(duì)逆境脅迫有不同表達(dá)響應(yīng)[36]。水稻中不同的PMEI成員對(duì)逆境的響應(yīng)在轉(zhuǎn)錄水平上存在調(diào)控差異[33]。
此外,研究發(fā)現(xiàn),過氧化物酶與PMEI有類似的表達(dá)模式。Paynel等研究發(fā)現(xiàn),鎘誘導(dǎo)下細(xì)胞壁中果膠糖醛酸的共價(jià)交聯(lián)增加且過氧化物酶活性和PME均有所增加[41]。在擬南芥中發(fā)現(xiàn)的PRX36與PMEI6均定位于細(xì)胞壁結(jié)構(gòu)域,且存在共表達(dá)。最近,利用免疫熒光共振能量轉(zhuǎn)移-熒光壽命成像,確定擬南芥中PMEI6和與其有共表達(dá)關(guān)系的過氧化物酶PRX36存在互作,PMEI介導(dǎo)的去甲酯化果膠平臺(tái)在PRX36錨定細(xì)胞壁結(jié)構(gòu)過程中具有重要作用[42]。這些與其他酶之間的互作表明PME與PMEI在植物生長發(fā)育過程中發(fā)揮作用的復(fù)雜性,其中關(guān)系值得進(jìn)一步研究。
3 PME和PMEI對(duì)植物生長發(fā)育的影響
大量研究表明,PME和PMEI介導(dǎo)的果膠去甲酯化修飾對(duì)植物的生長發(fā)育有重要影響。果膠的去甲酯化與細(xì)胞壁硬度密切相關(guān),去甲酯化的HG產(chǎn)生帶負(fù)電的羧基基團(tuán)可結(jié)合陽離子(如與Ca2+螯合)形成 “蛋箱結(jié)構(gòu)”,或固定Al3+。細(xì)胞快速擴(kuò)張時(shí)需要高甲酯化的果膠,當(dāng)停止生長后在PMEs作用下,低甲酯化的果膠排列在細(xì)胞外壁使細(xì)胞壁硬度改變[35,43]。PME和PMEI的調(diào)控和互作,介導(dǎo)的果膠甲酯度改變,對(duì)植物細(xì)胞壁性質(zhì)有重要影響,在植物種子萌發(fā)與花粉管發(fā)育、根部發(fā)育過程以及逆境響應(yīng)中均扮演了重要角色(圖3)[44]。
3.1 PME與PMEI影響種子萌發(fā)與花粉管發(fā)育
植物花粉管細(xì)胞壁主要由胼胝質(zhì)和纖維素組成,頂端花粉管壁的組成則幾乎完全是呈片層狀的單層果膠。在花粉管中,果膠的去甲酯化使細(xì)胞壁變硬,在分生組織及葉片中,去甲酯化的果膠分布較多影響細(xì)胞壁延展性[45-47]。
PME與PMEI對(duì)花粉管發(fā)育有重要影響。Bosch等研究發(fā)現(xiàn),在施加外源PME之后,煙草的發(fā)芽率與花粉管生長顯著降低,生長速度與PME濃度成反比[21]。Zhang等將甘藍(lán)BoPMEI1異源反義表達(dá)后發(fā)現(xiàn),擬南芥花粉管伸長受到抑制,且部分表現(xiàn)為雄性不育和結(jié)實(shí)率下降。體外試驗(yàn)表明,AtPMEI2在花粉管頂端特異表達(dá)抑制PME活性,且抑制AtPME1活性,從而調(diào)節(jié)花粉管外壁穩(wěn)定性[48]。在擬南芥的基因表達(dá)分析中,大量PME和PMEI特異地在花器官中表達(dá),這與其功能是相一致的。
黏液釋放是擬南芥種子在萌發(fā)過程中的重要過程,與去甲酯化的果膠有較大關(guān)聯(lián)。PME58是首個(gè)被確定對(duì)種皮黏液釋放有直接影響的PME基因。利用Ca2+螯合劑乙二胺四乙酸(EDTA)處理擬南芥種子,發(fā)現(xiàn)種皮周圍黏液釋放層擴(kuò)大[49]。PMEI6是控制種皮黏液釋放的關(guān)鍵基因,擬南芥PMEI6突變體中黏液釋放的初生壁與次生壁的交聯(lián)處變薄,使得種子在吸漲萌發(fā)后更易于將種皮黏液異常釋放[42]。
3.2 PME和PMEI影響根部和果實(shí)發(fā)育
PME與PMEI介導(dǎo)的果膠去甲酯化影響細(xì)胞壁結(jié)構(gòu),對(duì)果實(shí)發(fā)育、軟化、成熟過程均有影響。蘋果果實(shí)成熟過程中,乙烯和低溫可顯著提高PME活性,加速果實(shí)軟化。在番茄果實(shí)中,PME酶活性的降低對(duì)果實(shí)的果膠代謝產(chǎn)生影響,改變植物果實(shí)中可溶性糖和可溶性固形物含量[50]。此外,木質(zhì)部中高度甲酯化的果膠為蔗糖轉(zhuǎn)運(yùn)提供運(yùn)輸通道,從而影響光合產(chǎn)物積累與碳源分配[51]。草莓轉(zhuǎn)錄組數(shù)據(jù)表明,F(xiàn)vPME38和FvPME39均在成熟期高度表達(dá),且受到ABA調(diào)控,且二者的超表達(dá)植株與RNAi植株果實(shí)發(fā)育均受到影響[52]。果膠去甲酯化會(huì)影響根部發(fā)育,擬南芥中AtPME3參與不定根的形成,突變體的根部對(duì)Zn2+表現(xiàn)出敏感性。同時(shí),萌發(fā)提前、根毛減少、種子黏液釋放異常,且部分受體激酶以及GA相關(guān)基因表達(dá)下降,說明AtPME3參與調(diào)控了植物生長發(fā)育的多個(gè)過程[53]。研究發(fā)現(xiàn),在缺磷時(shí),粳稻日本晴中PME活性升高,難溶態(tài)磷釋放增加,根尖中果膠去甲酯化程度與難溶態(tài)磷的活化程度趨勢一致[54-55]。
3.3 PME和PMEI影響植物逆境響應(yīng)
PME介導(dǎo)的去甲酯化過程中釋放的甲醇可作為信號(hào)分子引起植物對(duì)逆境的響應(yīng)。產(chǎn)生的質(zhì)子引起胞內(nèi)pH值的改變?yōu)榧?xì)胞壁提供酸性環(huán)境,從而改變果膠降解酶如多聚半乳糖醛酸酶(polygalacturonase,PG)的活性。當(dāng)植物遭受病原體攻擊時(shí),PGs作用HG的裂解產(chǎn)物寡聚半乳糖醛酸(oligogalacturonide,OGA)可作為信號(hào)分子誘發(fā)植物防御機(jī)制(圖4)[56]。
在水稻中超表達(dá)OsPME14,植株根的生長受到抑制,表現(xiàn)出對(duì)鋁脅迫的敏感性[57]。將水稻中PME活性降低后發(fā)現(xiàn),細(xì)胞壁中鋁含量降低[58]。Liu等研究發(fā)現(xiàn),在GhPMEI3的基因沉默植株中,GhPME2、GhPME31與VdPG1的活性有所升高,抗病性減弱;而異源超表達(dá)植株下胚軸根毛增多,伸長區(qū)細(xì)胞形態(tài)改變,抗病性增強(qiáng)[32]。類似地,在AtPMEI2與AtPMEI3超表達(dá)植株中根長顯著增加,半乳糖醛酸總含量未變,但甲酯化水平提高約16%,對(duì)灰霉的抗性增強(qiáng)。反之,AtPMEI10、AtPMEI11、AtPMEI12的突變體植株均表現(xiàn)灰霉病抗性降低[48]。將楊樹PtoPME35在擬南芥異源超表達(dá)后,在甘露醇脅迫處理下可控制葉片氣孔開合,進(jìn)而調(diào)控植物抗逆性[59]。
4 展望
果膠影響細(xì)胞間的黏附性、流變性,其合成與修飾途徑影響著植物根部發(fā)育、花粉管萌發(fā)、器官建成以及逆境響應(yīng)。由果膠甲酯酶與果膠甲酯酶抑制子所介導(dǎo)的果膠去甲酯化修飾影響植物生長發(fā)育的多個(gè)過程,在種子萌發(fā)、花器官建成、根部與果實(shí)發(fā)育、逆境與脅迫響應(yīng)及細(xì)胞壁結(jié)構(gòu)中發(fā)揮重要作用。但在植物中,PME與PMEI均為多基因編碼家族蛋白,在發(fā)揮作用過程中的冗余現(xiàn)象目前仍需進(jìn)一步探討。另外,果膠的本身性質(zhì)受到PME和PMEI作用而改變,但越來越多的研究表明,果膠的改變造成整個(gè)細(xì)胞壁的性質(zhì)和結(jié)構(gòu)變化,而這一點(diǎn)在以前并沒有得到足夠的認(rèn)識(shí)[60-61]。由于去甲酯化的果膠與其他多種物質(zhì)存在交聯(lián),如果膠與細(xì)胞壁大分子纖維素間的交聯(lián)主要與果膠的甲酯度有關(guān)。而PME與PMEI是否參與這些交聯(lián)從而改變細(xì)胞壁結(jié)構(gòu)影響植物生長發(fā)育值得研究。此外,PMEI可同時(shí)對(duì)多個(gè)PME產(chǎn)生活性抑制作用,對(duì)于PME的抑制作用是否皆為廣譜性的抑制,其間的關(guān)聯(lián)機(jī)制分析可為未來的研究提供方向。
參考文獻(xiàn):
[1]Atmodjo M A,Hao Z,Mohnen D. Evolving views of pectin biosynthesis[J]. Annual Review of Plant Biology,2013,64:747-779.
[2]Pelloux J,Rusterucci C,Mellerowicz E J. New insights into pectin methylesterase structure and function[J]. Trends in Plant Science,2007,12:267-277
[3]Mohnen D. Pectin structure and biosynthesis[J]. Current Opinion in Plant Biology,2008,11(3):266-277.
[4]Harholt J,Suttangkakul A,Scheller H V. Biosynthesis of pectin[J]. Plant Physiology,2010,153(2):384-395.
[5]Wolf S,Mouille G,Pelloux J. Homogalacturonan methyl-esterification and plant development[J]. Molecular Plant,2009,2(5):851-860.
[6]Jolie R P,Duvetter T,van Loey A M,et al. Pectin methylesterase and its proteinaceous inhibitor:a review[J]. Carbohydrate Research,2010,345(18):2583-2595.
[7]Giovane A,Servillo L,Balestrieri C,et al. Pectin methylesterase inhibitor[J]. Biochimica et Biophysica Acta -Proteins and Proteomics,2004,1696(2):245-252.
[8]Lionetti V,Cervone F,Bellincampi D. Methyl esterification of pectin plays a role during plant-pathogen interactions and affects plant resistance to diseases[J]. Journal of Plant Physiology,2012,169(16):1623-1630.
[9]Markovicˇ O,Janecˇek Sˇ. Pectin methylesterases:sequence-structural features and phylogenetic relationships[J]. Carbohydrate Research,2004,339(13):2281-2295.
[10]Kohli P,Kalia M,Gupta R. Pectin methylesterases:a review[J]. Journal of Bioprocessing & Biotechniques,2015,5(5):1.
[11]Johansson K,El-Ahmad M,F(xiàn)riemann R,et al. Crystal structure of plant pectin methylesterase[J]. FEBS Letters,2002,514(2/3):243-249.
[12]di Matteo A,Giovane A,Raiola A,et al. Structural basis for the interaction between pectin methylesterase and a specific inhibitor protein[J]. The Plant Cell,2005,17(3):849-858.
[13]Dorokhov Y L,Skurat E V,F(xiàn)rolova O Y,et al. Role of the leader sequence in tobacco pectin methylesterase secretion[J]. FEBS Letters,2006,580(13):3329-3334.
[14]Hothorn M,Wolf S,Aloy P,et al. Structural insights into the target specificity of plant invertase and pectin methylesterase inhibitory proteins[J]. The Plant Cell,2004,16(12):3437-3447.
[15]Grasdalen H,Andersen A K,Larsen B. NMR spectroscopy studies of the action pattern of tomato pectinesterase:generation of block structure in pectin by a multiple-attack mechanism[J]. Carbohydrate Research,1996,289:105-114.
[16]Cameron R G,Luzio G A,Goodner K,et al. Demethylation of a model homogalacturonan with a salt-independent pectin methylesterase from citrus:Ⅰ. Effect of pH on demethylated block size,block number and enzyme mode of action[J]. Carbohydrate Polymers,2008,71(2):287-299.
[17]Duvetter T,F(xiàn)raeye I,Sila D N,et al. Mode of de-esterification of alkaline and acidic pectin methyl esterases at different pH conditions[J]. Journal of Agricultural and Food Chemistry,2006,54(20):7825-7831.
[18]Denès J M,Baron A,Renard C M G C,et al. Different action patterns for apple pectin methylesterase at pH 7.0 and 4.5[J]. Carbohydrate Research,2000,327(4):385-393.
[19]Bonnin E,Alvarado C,Crépeau M J,et al. Mobility of pectin methylesterase in pectin/cellulose gels is enhanced by the presence of cellulose and by its catalytic capacity[J]. Scientific Reports,2019,9(1):1-10.
[20]Micheli F. Pectin methylesterases:cell wall enzymes with important roles in plant physiology[J]. Trends in Plant Science,2001,6(9):414-419.
[21]Bosch M,Cheung A Y,Hepler P K. Pectin methylesterase,a regulator of pollen tube growth[J]. Plant Physiology,2005,138(3):1334-1346.
[22]Giovane A,Balestrieri C,Quagliuolo L,et al. A glycoprotein inhibitor of pectin methylesterase in Kiwi fruit:purification by affinity chromatography and evidence of a ripening‐related precursor[J]. European Journal of Biochemistry,1995,233(3):926-929.
[23]Jiang C M,Li C P,Chang J C,et al. Characterization of pectinesterase inhibitor in jelly fig (Ficus awkeotsang Makino) achenes[J]. Journal of Agricultural and Food Chemistry,2002,50(17):4890-4894.
[24]Dedeurwaerder S,Menu-Bouaouiche L,Mareck A,et al. Activity of an atypical Arabidopsis thaliana pectin methylesterase[J]. Planta,2009,229(2):311-321.
[25]梅曉宏,陳燕卉,高紅巖,等. 果膠甲酯酶抑制劑的研究進(jìn)展[J]. 食品科技,2008,33(6):64-68
[26]DAvino R,Camardella L,Christensen T M I E,et al. Tomato pectin methylesterase:modeling,fluorescence,and inhibitor interaction studies-comparison with the bacterial (Erwinia chrysanthemi) enzyme[J]. Proteins(Structure,F(xiàn)unction,and Bioinformatics),2003,53(4):830-839.
[27]Sénéchal F,Graff L,Surcouf O,et al. Arabidopsis PECTIN METHYLESTERASE17 is co-expressed with and processed by SBT3. 5,a subtilisin-like serine protease[J]. Annals of Botany,2014,114(6):1161-1175.
[28]Sénéchal F,Mareck A,Marcelo P,et al. Arabidopsis PME17 activity can be controlled by pectin methylesterase inhibitor4[J]. Plant Signaling & Behavior,2015,10(2):e983351.
[29]Turbant A,F(xiàn)ournet F,Lequart M,et al. PME58 plays a role in pectin distribution during seed coat mucilage extrusion through homogalacturonan modification[J]. Journal of Experimental Botany,2016,67(8):2177-2190.
[30]Shi D,Ren A,Tang X F,et al. MYB52 negatively regulates pectin demethylesterification in seed coat mucilage[J]. Plant Physiology,2018,176(4):2737-2749.
[31]Hong M J,Kim D Y,Lee T G,et al. Functional characterization of pectin methylesterase inhibitor (PMEI) in wheat[J]. Genes & Genetic Systems,2010,85(2):97-106.
[32]Liu N N,Sun Y,Pei Y K,et al. A pectin methylesterase inhibitor enhances resistance to Verticillium wilt[J]. Plant Physiology,2018,176(3):2202-2220.
[33]Nguyen H P,Jeong H Y,Kim H,et al. Molecular and biochemical characterization of rice pectin methylesterase inhibitors (OsPMEIs)[J]. Plant Physiology and Biochemistry,2016,101:105-112.
[34]Hocq L,Pelloux J,Lefebvre V. Connecting homogalacturonan-type pectin remodeling to acid growth[J]. Trends in Plant Science,2017,22(1):20-29.
[35]Pinzón-Latorre D,Deyholos M K. Characterization and transcript profiling of the pectin methylesterase (PME) and pectin methylesterase inhibitor (PMEI) gene families in flax (Linum usitatissimum)[J]. BMC Genomics,2013,14(1):742.
[36]Jeong H Y,Nguyen H P,Lee C. Genome-wide identification and expression analysis of rice pectin methylesterases:implication of functional roles of pectin modification in rice physiology[J]. Journal of Plant Physiology,2015,183:23-29.
[37]Tang C,Zhu X X,Qiao X,et al. Characterization of the pectin methyl-esterase gene family and its function in controlling pollen tube growth in pear (Pyrus bretschneideri)[J]. Genomics,2020,112(3):2467-2477.
[38]Ren A,Ahmed R I,Chen H,et al. Genome-wide identification,characterization and expression patterns of the pectin methylesterase inhibitor genes in Sorghum bicolor[J]. Genes,2019,10(10):755.
[39]Liu T,Yu H,Xiong X,et al. Genome-wide identification and characterization of pectin methylesterase inhibitor genes in Brassica oleracea[J]. International Journal of Molecular Sciences,2018,19(11):3338.
[40]Chen J,Chen X H,Zhang Q F,et al. A cold-induced pectin methyl-esterase inhibitor gene contributes negatively to freezing tolerance but positively to salt tolerance in Arabidopsis[J]. Journal of Plant Physiology,2018,222:67-78.
[41]Paynel F,Schaumann A,Arkoun M,et al. Temporal regulation of cell-wall pectin methylesterase and peroxidase isoforms in cadmium-treated flax hypocotyl[J]. Annals of Botany,2009,104(7):1363-1372.
[42]Francoz E,Ranocha P,Le Ru A,et al. Pectin demethylesterification generates platforms that anchor peroxidases to remodel plant cell wall domains[J]. Developmental Cell,2019,48(2):261-276.
[43]Carpin S,Crèvecoeur M,de Meyer M,et al. Identification of a Ca2+-pectate binding site on an apoplastic peroxidase[J]. The Plant Cell,2001,13(3):511-520.
[44]Wormit A,Usadel B. The multifaceted role of pectin methylesterase inhibitors (PMEIs)[J]. International Journal of Molecular Sciences,2018,19(10):2878.
[45]Palin R,Geitmann A. The role of pectin in plant morphogenesis[J]. Biosystems,2012,109(3):397-402.
[46]Hongo S,Sato K,Yokoyama R,et al. Demethylesterification of the primary wall by PECTIN METHYLESTERASE35 provides mechanical support to the Arabidopsis stem[J]. The Plant Cell,2012,24(6):2624-2634.
[47]Qi J,Wu B B,F(xiàn)eng S L,et al. Mechanical regulation of organ asymmetry in leaves[J]. Nature Plants,2017,3(9):724-733.
[48]Lionetti V,F(xiàn)abri E,de Caroli M,et al. Three pectin methylesterase inhibitors protect cell wall integrity for Arabidopsis immunity to Botrytis[J]. Plant Physiology,2017,173(3):1844-1863.
[49]Turbant A,F(xiàn)ournet F,Lequart M,et al. PME58 plays a role in pectin distribution during seed coat mucilage extrusion through homogalacturonan modification[J]. Journal of Experimental Botany,2016,67(8):2177-2190.
[50]Tieman D M,Harriman R W,Ramamohan G,et al. An antisense pectin methylesterase gene alters pectin chemistry and soluble solids in tomato fruit[J]. The Plant Cell,1992,4(6):667-679.
[51]Xu Y H,Sechet J,Wu Y B,et al. Rice sucrose partitioning mediated by a putative pectin methyltransferase and homogalacturonan methylesterification[J]. Plant Physiology,2017,174(3):1595-1608.
[52]Xue C,Guan S C,Chen J Q,et al. Genome wide identification and functional characterization of strawberry pectin methylesterases related to fruit softening[J]. BMC Plant Biology,2020,20(1):1-17.
[53]Guénin S,Hardouin J,Paynel F,et al. AtPME3,a ubiquitous cell wall pectin methylesterase of Arabidopsis thaliana,alters the metabolism of cruciferin seed storage proteins during post-germinative growth of seedlings[J]. Journal of Experimental Botany,2017,68(5):1083-1095.
[54]趙旭升,朱曉芳,吳 啟,等. 水稻根系果膠去甲酯化促進(jìn)細(xì)胞壁磷再利用的機(jī)制探究[J]. 土壤學(xué)報(bào),2018,55(5):1190-1198.
[55]Zhu X F,Wang Z W,Wan J X,et al. Pectin enhances rice (Oryza sativa) root phosphorus remobilization[J]. Journal of Experimental Botany,2015,66(3):1017-1024.
[56]Duan W K,Huang Z N,Song X M,et al. Comprehensive analysis of the polygalacturonase and pectin methylesterase genes in Brassica rapa shed light on their different evolutionary patterns[J]. Scientific
Reports,2016,6:25107.
[57]Yang X Y,Zeng Z H,Yan J Y,et al. Association of specific pectin methylesterases with Al‐induced root elongation inhibition in rice[J]. Physiologia Plantarum,2013,148(4):502-511.
[58]Zhu C Q,Cao X C,Bai Z G,et al. Putrescine alleviates aluminum toxicity in rice (Oryza sativa) by reducing cell wall Al contents in an ethylene‐dependent manner[J]. Physiologia Plantarum,2019,167(4):471-487.
[59]Yang W,Ruan M,Xiang M,et al. Overexpression of a pectin methylesterase gene PtoPME35 from Populus tomentosa influences stomatal function and drought tolerance in Arabidopsis thaliana[J]. Biochemical and Biophysical Research Communications,2020,523(2):416-422.
[60]Chung D,Pattathil S,Biswal A K,et al. Deletion of a gene cluster encoding pectin degrading enzymes in Caldicellulosiruptor bescii reveals an important role for pectin in plant biomass recalcitrance[J]. Biotechnology for Biofuels,2014,7(1):147.
[61]Biswal A K,Atmodjo M A,Li M,et al. Sugar release and growth of biofuel crops are improved by downregulation of pectin biosynthesis[J]. Nature Biotechnology,2018,36(3):249-257.