The aim of this study was to contrast the effects of drought stress on polyamine oxidases gene expression and activity as well as photosynthetic efficiency in relatively tolerant (Karoon) and sensitive (260) maize genotype.d Reduction in leaf relative water content as a result of drought led to increase in root growth, but diminished shoot growth indices. Under drought stress, activity of antioxidant enzyme, catalase, significantly increased in both genotypes, whereas significant higher activity of superoxide dismutase and peroxidase was only observed in Karoon genotype. Expression of polyamine oxidase (PAO) genes (zmPAO1, zmPAO2, zmPAO3, zmPAO4, zmPAO5, zmPAO6) and activity of enzymatic polyamine oxidation was increased in both genotypes under drought stress. The enhancement in PAO gene expression and enzyme activity was more prominent in Karoon cultivar compared to 260. Chlorophyll a fluorescence and fast induction kinetics were negatively influenced by drought stress. These parameters were more affected in 260 cultivar compared with Karoon. Our results suggest that under drought stress, higher activity of polyamine oxidase pathway in back-conversion of Spermine and spermidine to putrescine (protectant of photosynthetic apparatus) as well as higher antioxidant enzymes activity in Karoon cultivar, may play a role in higher efficiency of photosynthetic process in this cultivar.

中文翻译：

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干旱胁迫下玉米（Zea mays L.）基因型多胺氧化酶基因表达模式变化与光合效率对比

本研究的目的是对比干旱胁迫对相对耐受 (Karoon) 和敏感 (260) 玉米基因型中多胺氧化酶基因表达和活性以及光合效率的影响。干旱导致根系生长增加，但枝条生长指数下降。在干旱胁迫下，两种基因型的抗氧化酶、过氧化氢酶的活性均显着增加，而仅在 Karoon 基因型中观察到超氧化物歧化酶和过氧化物酶的活性显着升高。在干旱胁迫下，两种基因型的多胺氧化酶 (PAO) 基因 (zmPAO1、zmPAO2、zmPAO3、zmPAO4、zmPAO5、zmPAO6) 的表达和酶促多胺氧化的活性均增加。与 260 相比，Karoon 品种中 PAO 基因表达和酶活性的增强更为突出。叶绿素 a 荧光和快速诱导动力学受到干旱胁迫的负面影响。与 Karoon 相比，这些参数在 260 品种中受到的影响更大。我们的研究结果表明，在干旱胁迫下，多胺氧化酶途径在精胺和亚精胺向腐胺（光合装置保护剂）的反向转化中的更高活性以及 Karoon 品种更高的抗氧化酶活性，可能在更高的光合效率中发挥作用。在这个品种的过程中。