三种转基因甘薯响应PEG-6000模拟干旱胁迫的生理性差异

Physiological differences of three transgenic sweet potatoes in response to PEG-6000-imitated drought stress

干旱是农作物生长的重要影响因子。通过综合比较3种转基因甘薯对干旱胁迫响应的差异,阐明它们应对干旱胁迫的生理响应机制,为后续培育抗旱性强的甘薯品种奠定基础。在15%PEG-6000模拟的干旱胁迫条件下,分别以氧化诱导型启动子SWPA2驱动的转Cu/Zn SOD&APX基因株系、组织特异型启动子SPO驱动的转IbMYB1基因株系和组成型启动子CaMV 35S驱动下的转IbOr基因株系及其各自的野生型对照为供试材料,研究了干旱胁迫条件下3种转基因甘薯的光合指标和抗氧化酶的变化特征,明确3种基因型的抗旱机理。结果表明:随着胁迫时间的延长,3种甘薯品种的净光合速率(Pn)、叶绿素含量和类胡萝卜素含量都持续降低,但3种转基因株系比非转基因对照降幅小,其中转Cu/Zn SOD&APX基因甘薯降幅最小。3种甘薯品种的花青素含量、H2O2和MDA含量都随胁迫时间的延长呈上升趋势,但转基因株系比非转基因对照的H_(2)O_(2)和MDA含量升幅小,其中转Ib MYB1基因甘薯花青素累积约为胁迫前的2.5倍左右。干旱胁迫后,甘薯叶片中类胡罗卜素含量随胁迫时间的延长而降低,转IbOr基因株系类胡萝卜素含量显著高于对照。甘薯的抗氧化酶(SOD、POD、APX、CAT)活性随胁迫时间的延长呈先升后降的趋势,其中,转Cu/Zn SOD&APX基因株系的抗氧化酶活性升高幅度最大,抗氧化能力最强。干旱胁迫后转IbMYB1甘薯DPPH清除能力一直维持在较高水平,表明非酶促抗氧化能力较强。综合分析表明转Cu/Zn SOD&APX株系抗旱性最强,转IbMYB1基因株系次之,转IbOr基因株系抗旱性较弱。转Cu/Zn SOD&APX基因甘薯通过较强的抗氧化酶活性以减轻氧化伤害作用,从而保持较高的叶绿素含量和类胡萝卜素含量,进而维持较高的净光合速率,提高抗旱性。转IbMYB1基因株系主要通过非酶促的抗氧化剂花青素含量的提高和较强的DPPH清除能力以保护叶绿体,从而增强光合能力,提高抗旱性。而转IbOr基因株系主要通过类胡萝卜素含量的累积来清除活性氧,保护叶绿体结构,减少膜脂氧化损伤,从而提高对干旱胁迫的抗性。

Drought is an important factor affecting crop growth.The physiological response mechanism of three transgenic sweet potatoes to drought stress was elucidated through comprehensive comparison of their responses to drought stress,which laid a foundation for the subsequent cultivation of sweet potato varieties with strong drought resistance.Under 15%PEG-6000 simulated drought stress conditions,transgenic lines of Cu/Zn SOD&APX gene driven by oxidation-induced promoter SWPA2,transgenic lines of Ib-MYB1 gene driven by tissue-specific promoter SPO,transgenic lines of IbOr gene driven by constitutive promoter CaMV 35S and their wild type controls were used as test materials,respectively.The changes of photosynthetic indexes and antioxidant enzymes of three transgenic sweet potatoes under drought stress were studied,and the drought resistance mechanism of three genes was clarified.The results indicate that,with the extension of stress time,the net photosynthetic rate(Ph),chlorophyll content and carotenoid content of the three sweet potato varieties continued to decrease,but the decrease of the three transgenic lines was less than that of the non-transgenic control,and the decrease of Cu/Zn SOD&APX gene sweet potato was the least.The anthocyanin content,H,O2 and MDA content of the three sweet potato varieties increased with the extension of stress time,but the increase of H,O2 and MDA contents of the transgenic line were less those that of the non-transgenic control,and the accumulation of anthocyanin in the transgenic sweet potato with IbMYB1 gene was about 2.5 times of that before stress.After drought stress,the carotenoid content in sweet potato leaves decreased with the extension of stress time,and the carotenoid content of IbOr transgenic lines was significantly higher than that of the control.The activities of antioxidant enzymes(SOD,POD,APX,CAT)of sweet potato varieties increased firstly and then decreased with the extension of stress time,among which,the activity of antioxidant enzymes increased the most and the antioxidant capacity was the strongest in Cu/Zn SOD&APX transgenic lines.DPPH scavenging capacity of transgenic IbMYB1 sweet potato was maintained at a high level after drought stress,indicating strong non-enzymatic antioxidant capacity.The comprehensive analysis showed that Cu/Zn SOD&APX and Ib-MYB1 lines had the highest drought resistance,followed by IbMYB1 gene lines,and IbOr gene lines had a weak drought resistance.The Cu/Zn SOD&APX transgenic sweet potato could reduce oxidative damage through stronger antioxidant enzyme activity,thus maintaining higher chlorophyll content and carotenoid content,and thus maintaining higher net photosynthetic rate and improving drought resistance.Transgenic lines with IbMYB1 gene protected chloroplasts by increasing the content of anthocyanin,a non-enzymatic antioxidant,and strong DPPH scavenging ability,thus enhancing photosynthetic capacity and drought resistance.However,the IbOr transgenic lines could eliminate reactive oxygen species(Ros),protect chloroplast structure,reduce membrane lipid oxidation damage,and improve the resistance to drought stress through the accumulation of carotenoid content.