周 娟,范紅麗,白麗甜,鄭 蕊,岳思君
(寧夏大學(xué)生命科學(xué)學(xué)院,寧夏銀川 750021)
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模擬干旱脅迫對(duì)發(fā)狀念珠藻抗氧化酶系統(tǒng)和滲透調(diào)節(jié)物質(zhì)的影響
周 娟,范紅麗,白麗甜,鄭 蕊,岳思君
(寧夏大學(xué)生命科學(xué)學(xué)院,寧夏銀川 750021)
【目的】探討模擬干旱脅迫對(duì)發(fā)狀念珠藻抗氧化酶系統(tǒng)和滲透調(diào)節(jié)物質(zhì)的影響。【方法】以發(fā)狀念珠藻細(xì)胞為實(shí)驗(yàn)材料,用2%、4%、6%、8%、10%濃度的 PEG-6000模擬干旱脅迫,測(cè)定發(fā)狀念珠藻氧化物歧化酶(SOD)、過(guò)氧化氫酶(CAT)、過(guò)氧化物酶(POD)活性及胞外多糖(EPS)和脯氨酸(Pro)含量的變化?!窘Y(jié)果】與對(duì)照處理相比,隨著干旱脅迫程度的增加,發(fā)狀念珠藻細(xì)胞的超氧化物歧化酶(SOD)、過(guò)氧化氫酶(CAT)、過(guò)氧化物酶(POD)活性均呈現(xiàn)先上升后下降的趨勢(shì),細(xì)胞胞外多糖(EPS)和脯氨酸(Pro)含量呈增加趨勢(shì),但在高濃度的脅迫下,脯氨酸的含量呈現(xiàn)下降趨勢(shì)。【結(jié)論】發(fā)狀念珠藻在中度干旱脅迫下能夠激活自身的抗氧化酶類(lèi)以提高藻細(xì)胞的抗氧化能力,從而能消除或減輕活性氧毒害,而在重度干旱脅迫下,酶活降低,標(biāo)志活性氧清除機(jī)制受到破壞,抗氧化能力降低。在干旱脅迫下,作為滲透調(diào)節(jié)物質(zhì)的胞外多糖和脯氨酸表現(xiàn)出緩解干旱脅迫的效果,累積的脯氨酸和胞外多糖能夠維持細(xì)胞內(nèi)滲透平衡,保證細(xì)胞內(nèi)正常的物質(zhì)代謝,從而提高發(fā)狀念珠藻對(duì)干旱脅迫的適應(yīng)性。
發(fā)狀念珠藻;干旱脅迫;抗氧化酶系統(tǒng);滲透調(diào)節(jié)物質(zhì)
1.1 材 料
實(shí)驗(yàn)選用的藻種為人工培養(yǎng)的發(fā)狀念珠藻(Nostocflagelliforme)懸浮細(xì)胞,由實(shí)驗(yàn)室篩選。
1.2 方 法
1.2.1 試驗(yàn)設(shè)計(jì)
用聚乙二醇(PEG-6000)為脅迫介質(zhì)模擬干旱實(shí)驗(yàn),以BG110為基本培養(yǎng)基,設(shè)置PEG-6000的實(shí)驗(yàn)濃度分別為0、2%、4%、6%、8%、10%,取20 mL藻液接種于180 mL含有PEG-6000的BG110培養(yǎng)基中,以不含PEG-6000的培養(yǎng)液作為對(duì)照組。光照搖床培養(yǎng)至第8 d進(jìn)行各項(xiàng)指標(biāo)的測(cè)定。
1.2.2 測(cè)定指標(biāo)
培養(yǎng)8 d后,每組三個(gè)重復(fù),離心收集藻細(xì)胞(8 000 r,15 min),用分析天平稱(chēng)取鮮重。 采用NBT光還原法測(cè)定SOD活性,采用愈創(chuàng)木酚法測(cè)定POD活性、采用紫外吸收法CAT活性測(cè)定活性,具體步驟參考史明科等[10]方法。以能抑制 NBT 50%的光化還原反應(yīng)時(shí)加入的酶量為1個(gè)SOD酶單位。POD酶活性以1 min內(nèi)A470變化0.01為1個(gè)酶活力單位(U) ,CAT酶活性用1 min內(nèi)分解 H2O21 mg為1個(gè)酶活力單位(U) 。胞外多糖含量測(cè)定采用苯酚-硫酸法[11];脯氨酸含量測(cè)定采用磺基水楊酸法[12]。
2.1 干旱脅迫對(duì)發(fā)狀念珠藻抗氧化酶系統(tǒng)的影響
2.1.1 SOD活性的影響
PEG模擬干旱脅迫對(duì)發(fā)狀念珠藻中SOD活性影響明顯。結(jié)果表明,發(fā)狀念珠藻的SOD活性隨干旱程度加劇呈現(xiàn)先增加后下降的趨勢(shì),當(dāng)PEG濃度在2%~6%,SOD活性逐漸增大,說(shuō)明此時(shí)藻細(xì)胞內(nèi)清除自由基和抗氧化能力增加,在濃度為8%~10%,SOD活性呈現(xiàn)下降趨勢(shì),但酶活性均明顯高于對(duì)照測(cè)定結(jié)果,說(shuō)明此時(shí)干旱脅迫對(duì)細(xì)胞的傷害程度加劇,進(jìn)一步抑制了SOD活性,但SOD依然能夠有效緩解干旱誘導(dǎo)產(chǎn)生的氧化脅迫。圖1
圖1 干旱脅迫下發(fā)狀念珠藻細(xì)胞SOD活性變化
Fig.1 Effect of drought stress on activity of SOD in Nostoc flagelliforme cell
2.1.2 POD活性的影響
干旱脅迫下POD活性表現(xiàn)出雙峰變化,POD活性在2%和8%達(dá)到兩個(gè)峰值。在2%的低濃度干旱脅迫時(shí),POD 活性上升,說(shuō)明此時(shí)膜脂氧化作用較輕,膜相對(duì)通透性增加較小。在4%和6%濃度時(shí),POD活性緩慢下降,在干旱脅迫濃度為8%時(shí)達(dá)到另一個(gè)峰值,隨后POD活性下降,此時(shí)膜脂過(guò)氧化作用過(guò)強(qiáng),膜通透性增大,對(duì)細(xì)胞的傷害較大。圖2
2.1.3 CAT活性的影響
隨著PEG濃度的升高,干旱脅迫的加劇,CAT活性呈現(xiàn)先升高后下降的趨勢(shì),說(shuō)明CAT在有效清除活性氧中發(fā)揮了作用,而CAT活性下降說(shuō)明在高濃度的干旱脅迫下,細(xì)胞嚴(yán)重受損,同時(shí)CAT活性在一定程度上受到抑制,活力逐漸下降。圖3
圖2 干旱脅迫下發(fā)狀念珠藻細(xì)胞POD活性變化
Fig.2 Effect of drought stress on activity of POD in Nostoc flagelliformecell
圖3 干旱脅迫下發(fā)狀念珠藻細(xì)胞CAT活性變化
Fig.3 Effect of drought stress on activity of CAT in Nostoc flagelliforme cell
2.2 干旱脅迫對(duì)發(fā)狀念珠藻滲透調(diào)節(jié)物質(zhì)的影響
2.2.1 胞外多糖含量的影響
在實(shí)驗(yàn)濃度范圍內(nèi),脅迫處理的胞外多糖含量明顯高于對(duì)照,且胞外多糖的含量隨著干旱脅迫濃度的增大而增大,胞外多糖含量隨干旱脅迫強(qiáng)度的變化說(shuō)明,胞外多糖可能是發(fā)狀念珠藻抵抗干旱逆境有關(guān)的物質(zhì),在干旱脅迫時(shí)對(duì)細(xì)胞起保護(hù)作用。圖4
2.2.2 脯氨酸(Pro)含量的影響
當(dāng)受到干旱脅迫時(shí),細(xì)胞中游離脯氨酸含量會(huì)有很大的變化。當(dāng)PEG濃度在2%~8%,脯氨酸含量呈現(xiàn)上升狀態(tài),隨著脅迫濃度的增大,脯氨酸含量呈現(xiàn)下降趨勢(shì)。說(shuō)明干旱脅迫條件下,細(xì)胞會(huì)積累脯氨酸保護(hù)細(xì)胞免受傷害,但當(dāng)脅迫濃度過(guò)高時(shí),細(xì)胞膜氧化作用加強(qiáng),膜系統(tǒng)進(jìn)一步受到傷害,細(xì)胞膜滲透性增強(qiáng),游離脯氨酸通過(guò)細(xì)胞膜滲透到培養(yǎng)液中,含量隨之下降。圖5
圖4 干旱脅迫下發(fā)狀念珠藻胞外多糖含量變化
Fig.4 Effect of drought stress on EPS content of Nostoc flagelliforme cell
圖5 干旱脅迫下發(fā)狀念珠藻脯氨酸含量變化
Fig.5 Effect of drought stress on Pro content of Nostoc flagelliforme
干旱脅迫下,生物體內(nèi)會(huì)產(chǎn)生大量的自由基,抗氧化酶能有效地清除細(xì)胞內(nèi)活性氧自由基[13]。SOD、POD 和CAT 是活性氧清除酶系統(tǒng)中最重要的保護(hù)酶,SOD 能夠催化氧自由基轉(zhuǎn)變?yōu)镠2O2,POD與CAT則能有效清除H2O2,減少細(xì)胞受到傷害[14]。在研究中,PEG起到水分脅迫作用,隨著PEG脅迫濃度的升高,SOD、POD、CAT活性呈現(xiàn)先升高后降低的趨勢(shì),說(shuō)明干旱脅迫誘導(dǎo)了發(fā)狀念珠藻抗氧化保護(hù)酶系統(tǒng)清除自由基能力,在低濃度PEG脅迫下,抗氧化酶酶活隨脅迫強(qiáng)度增加而提高,對(duì)活性氧具有防御作用,能有效清除活性氧,降低活性氧對(duì)細(xì)胞的損傷。但在高濃度PEG 脅迫下,細(xì)胞會(huì)產(chǎn)生更多的自由基,使細(xì)胞膜系統(tǒng)遭到破壞,加劇細(xì)胞受損程度,各類(lèi)抗氧化酶在一定程度上受到抑制,活力逐漸下降。
滲透調(diào)節(jié)是植物抗旱的一種重要的生理機(jī)制,與植物耐旱性有密切關(guān)系[15]。在干旱脅迫下,脯氨酸、多糖等滲透調(diào)節(jié)物質(zhì)能降低滲透勢(shì),還可以保護(hù)細(xì)胞許多重要代謝活動(dòng)所需的酶類(lèi),保證細(xì)胞內(nèi)正常生理功能[16]。研究結(jié)果表明,在模擬干旱脅迫下,胞外多糖和脯氨酸含量會(huì)隨著脅迫濃度的增加而增加,說(shuō)明干旱脅迫下細(xì)胞會(huì)通過(guò)促進(jìn)積累胞外多糖和脯氨酸來(lái)增強(qiáng)其滲透調(diào)節(jié)能力,進(jìn)而能夠降低細(xì)胞滲透勢(shì),維持細(xì)胞的正常水分平衡。但當(dāng)脅迫濃度過(guò)高時(shí),脯氨酸含量會(huì)逐漸下降,說(shuō)明高濃度PEG處理下細(xì)胞膜氧化作用加強(qiáng),細(xì)胞膜滲透性增強(qiáng)導(dǎo)致脯氨酸滲透到培養(yǎng)液中。而多糖在高濃度下會(huì)持續(xù)積累,也說(shuō)明脯氨酸和多糖之間存在相互補(bǔ)償作用。
4.1 干旱脅迫會(huì)導(dǎo)致植物體內(nèi)活性氧的累積,耐旱植物通過(guò)調(diào)節(jié)其抗氧化酶系統(tǒng)和滲透調(diào)節(jié)物質(zhì)來(lái)維持平衡,顯示出一定的耐旱能力。在干旱脅迫下發(fā)狀念珠藻抗氧化酶活性和滲透調(diào)節(jié)物質(zhì)的含量發(fā)生明顯變化,在中度干旱脅迫下,隨著PEG脅迫濃度的升高,發(fā)狀念珠藻SOD、POD、CAT活性均呈現(xiàn)增加趨勢(shì),SOD活性由459.41U/g增加到2 134.01 U/g,POD活性由22.83 U/g增加到262.64 U/g,CAT活性由5.78 U/g增加到47.58 U/g,這些抗氧化酶活性的增加有效維的持了活性氧積累與清除的平衡,在重度干旱脅迫下,酶活性呈現(xiàn)下降趨勢(shì),SOD、POD、CAT活性分別下降到634.74 U/g、52.64 U/g、5.58 U/g,說(shuō)明當(dāng)遭受干旱脅迫時(shí),發(fā)狀念珠藻能通過(guò)增強(qiáng)抗氧化酶活性的方式來(lái)有效清除活性氧,調(diào)節(jié)活性氧代謝的平衡,降低細(xì)胞受傷害的程度。然而,隨著細(xì)胞受傷害程度的加劇,活性氧大量累積會(huì)造成部分活性氧清除機(jī)制的破壞,抗氧化酶活性降低。同時(shí),脯氨酸和胞外多糖的含量也發(fā)生了很大變化,胞外多糖含量呈上升趨勢(shì),由0.002 mg/mL上升到0.09 mg/mL。脯氨酸含量呈先上升后下降趨,由20.89 μg/g上升到39.04 μg/g,隨后又下降到32.14 μg/g。胞外多糖和脯氨酸承擔(dān)起調(diào)節(jié)細(xì)胞滲透勢(shì)的作用,脯氨酸和多糖的累積可降低細(xì)胞水勢(shì)、減少細(xì)胞由于脫水造成的傷害,增強(qiáng)發(fā)狀念珠藻的耐旱能力。
4.2 干旱脅迫下的發(fā)狀念珠藻有較強(qiáng)的活性氧清除能力,而且能通過(guò)增加滲透調(diào)節(jié)物質(zhì)的含量來(lái)保持較高的滲透調(diào)節(jié)能力,因此滲透調(diào)節(jié)物質(zhì)的大量累積及抗氧化酶系統(tǒng)的調(diào)節(jié),是發(fā)狀念珠藻對(duì)干旱脅迫適應(yīng)的重要生理響應(yīng),也是發(fā)狀念珠藻長(zhǎng)期適應(yīng)干旱環(huán)境的結(jié)果。
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Fund project:Supported by NSFC (Grant No. 31360025 and No. 31560418)
Effect of Simulated Drought Stress on Antioxidant System and Osmotic Regulation in Cells ofNostocflagelliforme
ZHOU Juan, FAN Hong- li, BAI Li-tian, ZHENG Rui, YUE Si-jun
(CollegeofLifeSciences,NingxiaUniversity,Yinchuan750021,China)
【Objective】 The objective of this study is to explore the effect of different drought stress on antioxidant system activety and osmotic regulation substance contents ofNostocflagelliforme. 【Method】TheNostocflagelliformecells were used as experimental materials and PEG-6000 with different concertrations (0,2%, 4%, 6%, 8%, 10%) were used to simulate the water stress. And the change of superoxide dismutase (SOD),peroxidase (POD), catalase (CAT) activrty and the content of extracellular polysaccharide (EPS), proline (Pro) ofNostocflagelliformewere determined. 【Result】The results showed that the contents ofNostocflagelliformeSOD, POD, CAT activity first increased,and then declined.The content of proline(Pro) and extracellular polysaccharide(EPS) always increased under the low drought treatment, but the proline content showed a trend of decline under the servere drought reatment 【Conclusion】The research illustrated under medium drought treatment the antioxidant enzyme of nostoc flagelliforme adjusted itself to increase its antioxidant capability. This can avoid active oxygen species injury. But under severe drought treatment, the capability has already fallen down obviously because some active oxygen scavenging was destroyed. Under drought stress treatment, extracellular polysaccharide and proline of osmotic regulation substances showed the effect of alleviating drought stress, and the accumulation of proline and extracellular polysaccharide could maintain intracellular osmotic balance and ensure normal metabolism in cells, which is likely to improve the adaptability ofNostocflagelliformeunder drought stress.
Nostocflagelliforme;drought stress;antioxidant enzyme system;osmotic regulation
10.6048/j.issn.1001-4330.2016.05.018
2015-12-04
國(guó)家自然科學(xué)基金項(xiàng)目(31360025,31560418)
周娟(1989 -),女,寧夏人,碩士研究生,研究方向?yàn)槲⑸锛夹g(shù)與工程,(E-mail):zhoujuanlee@163.com
岳思君(1972-),男,寧夏人,副教授,碩士生導(dǎo)師,研究方向?yàn)槲⑸飳W(xué)、發(fā)酵工程,(E-mail):sijunyue@126.com
S188
A
1001-4330(2016)05-0915-06