S-腺苷甲硫氨酸脱羧酶基因对银腺杨84K抗旱性的影响

Effects of S-Adenosylmethionine Decarboxylase Gene on Drought Tolerance of Populus alba×P.glandulosa‘84K’

【目的】多胺广泛存在于植物体内,参与调节植物发育过程以及胁迫响应,S-腺苷甲硫氨酸脱羧酶(SAMDC)是多胺合成途径的关键限速酶。本研究以SAMDC转基因银腺杨84K为材料,分析在干旱胁迫下SAMDC对杨树生长的影响,探讨SAMDC在林木响应干旱中的作用,为揭示多胺在杨树抗逆性方面的作用提供参考。【方法】以生长3个月的银腺杨84K及其PagSAMDC4a过表达转基因株系的土培苗为试验材料进行干旱处理,观察植株表型,并对多胺含量、H2O_(2)含量、叶片相对含水量、叶片失水率、电解质渗透率等生理指标进行分析。【结果】PagSAMDC4a过表达银腺杨84K株系PagSAMDC4a-OE#3、PagSAMDC4a-OE#15、PagSAMDC4a-OE#17的内源亚精胺、精胺含量都显著高于未转基因植株,且PagSAMDC4a-OE#17株系内源腐胺、亚精胺、精胺含量分别是未转基因植株的1.95、3.43、1.32倍。正常条件下,过表达PagSAMDC4a植株的叶片表型、叶片相对含水量和电解质渗透率与未转基因植株无显著差异,而过表达株系PagSAMDC4a-OE#15和PagSAMDC4a-OE#17的叶片失水率显著低于未转基因植株。在干旱胁迫下,未转基因银腺杨84K叶片萎蔫,相对含水量比正常情况下降低26.44%,电解质渗透率升高27.68%,而PagSAMDC4a-OE#3、PagSAMDC4a-OE#15、PagSAMDC4a-OE#17植株叶片生长正常,相对含水量比正常条件下分别降低了10.9%、3.66%、1.33%,电解质渗透率较低、变化幅度较小。与未转基因植株相比,过表达PagSAMDC4a的转基因植株正常条件下H2O_(2)含量显著降低;在干旱胁迫后,H2O_(2)含量虽有增加但幅度显著低于未转基因植株,H2O_(2)含量由高到低为未转基因植株>PagSAMDC4a-OE#3>PagSAMDC4a-OE#15>PagSAMDC4a-OE#17。【结论】PagSAMDC4a可以调控银腺杨84K内源多胺含量,过表达PagSAMDC4a基因使植株内源多胺含量升高、H2O_(2)含量降低,减轻干旱胁迫引起的氧化损伤,进而有效缓解植株叶片所受水分胁迫,从而降低植株对干旱的敏感性。因此,可以通过调控SAMDC4a过表达影响内源多胺水平的变化从而调控干旱胁迫适应过程。

【Objective】Polyamines exist widely in plants,and are involved in the regulation of plant development and stress response.S-adenosylmethionine decarboxylase(SAMDC)is a key rate-limiting enzyme in the polyamine biosynthesis pathway.In this study,the role of SAMDC in poplar 84K(Populus alba×P.glandulosa‘84K’)under drought stress was analyzed using SAMDC overexpressing plants.This work will lay on important foundation for the elucidation of the role of polyamines in stress tolerance.【Method】The nontransgenic(control)and transgenic PagSAMDC4a overexpressing poplar 84K plants growing in soil for 3 months were used and subjected to drought treatment to analyze phenotypic and physiological changes,including polyamines content,H2O_(2) content,relative water content of leaves,water loss rate of leaves,electrolytic leakage and so on.【Result】The contents of endogenous spermidine and spermine in PagSAMDC4a-OE#3,PagSAMDC4a-OE#15 and PagSAMDC4a-OE#17 transgenic poplars were significantly higher than those in nontransgenic control,and the contents of endogenous putrescine,spermidine and spermine in PagSAMDC4a-OE#17 transgenic plant were 1.95,3.43 and 1.32 times higher than those in control,respectively.Under normal conditions,compared with nontransgenic control,leaf phenotype,leaf relative water content and electrolytic leakage of overexpressing plants had no significant differences,while the water loss rate of PagSAMDC4a-OE#15 and PagSAMDC4a-OE#17 plants were significantly lower than that of control.Under drought stress,the leaves of nontransgenic plants were wilted,the relative water content decreased by 26.44%and the electrolytic leakage increased by 27.68%.However,PagSAMDC4a-OE plants grew normally,and the relative water content of overexpressing PagSAMDC4a-OE#3,PagSAMDC4a-OE#15 and PagSAMDC4a-OE#17 plants decreased by 10.9%,3.66%and 1.33%,respectively.The overexpressing plants had low electrolytic leakage and a small variation.Under normal conditions,H2O_(2) contents of PagSAMDC4a transgenic plants were significantly reduced.Under the drought stress,the increase of H2O_(2) content of PagSAMDC4a overexpressing plants was significantly lower than that of nontransgenic plants,and the content variation from high to low was nontransgenic plant>PagSAMDC4a-OE#3>PagSAMDC4a-OE#15>PagSAMDC4a-OE#17.【Conclusion】Overexpression of PagSAMDC4a gene can increase endogenous polyamines and decrease H2O_(2) content in poplar 84K,which can reduce the oxidative damage caused by drought stress and effectively alleviate the water stress damage suffered by the plant leaves,contributing to relieving the sensitivity of poplar to drought stress.Therefore,SAMDC4a could affect the changes of endogenous polyamines in response to drought stress.