干旱胁迫下外源ABA对甘蔗幼苗生理特性和基因表达的影响

Effects of Exogenous ABA on Physiological Characteristics and Gene Expression in Sugarcane Seedlings under Drought Stress

甘蔗是世界上重要的糖料作物,但我国甘蔗主产区多数为丘陵旱坡地,季节性干旱频繁,已严重影响我国甘蔗糖业的可持续发展。植物激素脱落酸(ABA)不仅调节植物生长发育,在植物应对逆境胁迫的生理生化响应中更不可或缺。本研究选用甘蔗品种‘桂糖42号’为材料,桶栽土培方式,设置对照(CK)、CK+ABA、干旱、干旱+ABA等4个处理,探讨干旱胁迫下叶面喷施ABA对苗期甘蔗生理生化特性和相关基因表达的影响,为应用ABA提高甘蔗抗旱性提供理论基础。结果表明,正常淋水条件下甘蔗叶面喷施ABA处理(CK+ABA)的主要生理生化参数与基因表达量变化与CK差异不显著;甘蔗叶片相对含水量随着干旱胁迫程度加剧而逐渐下降,丙二醛(MDA)、过氧化氢(H2O2)含量显著上升,而干旱+ABA处理能提高甘蔗的保水能力,并减少MDA的积累,使其含量处于较低水平;干旱胁迫显著降低甘蔗叶绿素含量,而干旱+ABA处理能防止叶绿素降解并对干旱胁迫引起的光系统Ⅱ实际光化学效率(ΦPSⅡ)下降有明显的缓解作用;干旱胁迫下,甘蔗内源ABA合成限速酶9-顺式-环氧类胡萝卜素双加氧酶(NCED)编码基因、脯氨酸(Pro)合成关键酶Δ1-吡咯啉-5-羧酸合成酶(P5CS)编码基因及过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、过氧化物酶(POD)编码基因的表达量显著增加,内源ABA含量、Pro含量和CAT、SOD、APX、POD活性显著提高,而干旱+ABA处理能更进一步增强上述基因的表达,使ABA含量、Pro含量及相关抗氧化酶活性的增幅更显著,从而提高干旱胁迫下甘蔗清除过量活性氧的能力,降低H2O2含量,提高甘蔗抗旱性。

Sugarcane is an important sugar crop in the world,but the main sugarcane producing areas in China are hilly and dry slopes,and seasonal droughts occur frequently due to the uneven distribution of rainfall.Droughts do great harm to yield and quality and the sustainable development of sugarcane industry in China.The plant hormone abscisic acid(ABA)not only regulates plant growth and development,but also plays an important role in the physiological and biochemical responses of plants environmental stresses.In this study,we used sugarcane(Saccharum officinarum L.)variety‘Guitang 42’as the material to investigate the effects of exogenous ABA on leaf physiological characteristics and gene expressions under water stress condition in treatments control(normal irrigation),control+ABA,drought(stop irrigation),drought+ABA.The foliar application of 15μmol/L ABA was sprayed twice in two days before drought stress given.The results showed that the changes of main physiological and biochemical parameters and gene expression in control+ABA treatment were not significantly different from those of the control.The leaf relative water content(RWC)was gradually decreased by drought treatment but it could maintain higher in drought+ABA treatment.The drought treatment could result in an increase in malondialdehyde(MDA)and hydrogen peroxide(H2O2)content,but the plants applied with ABA were found to resist the excessive accumulation of MDA.Drought stress significantly reduced the leaf chlorophyll content in sugarcane,but the exogenous ABA application decreased the degradation of chlorophyll,counteracted,at least in part,the decrease in quantum efficiency of PSII(ΦPSII).The expression of gene encoding 9-cis-epoxycarotenoid dioxygenase(NCED)for ABA biosynthesis,the genes encodingΔ1-pyrroline-5-carboxylate syn-thase(P5CS)for proline biosynthesis,and the antioxidant enzymes catalase(CAT),superoxide dismutase(SOD),ascorbate peroxidase(APX),peroxidase(POD)encoding genes was significantly increased in the leaf under water stress condition,following the significantly higher endogenous ABA content,proline content and CAT,SOD,APX and POD activities in water stress treatment as compared to the control.But exogenous ABA application under water stress could further enhance the expression of the genes,hence further improved the ABA content,proline content and related antioxidant enzyme activity.The results clearly suggests that the foliar ABA application could triggering the over expression of antioxidative defense system,and improve drought tolerance of sugarcane under water stress condition.