Drought tolerance in apple seedlings through abscisic acid (ABA) regulation

本研究研究了一种ABA 8′-羟化酶（AHI）抑制剂对苹果幼苗抗旱性的影响。研究了干旱条件下叶片ABA代谢、气孔开度、水势和自由基清除活性。我们的观察结果表明，与未经处理的对照样品相比，施用AHI的幼苗叶片气孔孔径明显减小。然而，给AHI处理过的植物浇水后，它又恢复到原来的水平。此外，干旱期间，ahi处理叶片的水势仍然高于未处理叶片的水势。干旱条件增加了AHI处理和未处理植物标本中的ABA浓度。值得注意的是，干旱条件下，ahi处理叶片的ABA浓度高于未处理叶片。虽然9-顺式环氧类胡萝卜素二氧合酶（MdNCED）基因的表达随干旱胁迫处理天数的增加而增加，但在ahi处理的叶片中，这些基因的表达量显著低于未处理的对照样品。这些结果表明，在相对较长的干旱条件下，植物可能需要通过ABA 8′-羟化酶的调节来迅速关闭气孔。

In this study, we examined the effect of an inhibitor of ABA 8'-hydroxylase (AHI) on drought tolerance in apple seedlings (Malus domestica Borkh.). ABA metabolism, stomatal aperture, water potential, and radical scavenging activity in leaves were all investigated under drought conditions. The result of our observation had shown that the AHI application to seedlings greatly decreased the stomatal aperture in the leaves as in contrast to untreated control samples.However, watering of AHI treated plants re-increased it to the original level. In addition, water potential in AHI-treated leaves remained higher than the one measured in untreated-leaves during the exposure to drought. Drought conditions increased ABA concentrations in both, AHI treated-plants and untreated-plant specimens. Notably, ABA concentrations in AHI-treated leaves were higher than those in untreated-leaves under drought conditions. Although the expression of 9-cis-epoxycarotenoid dioxigenase (MdNCED) genes increased with days of drought stress treatment, in AHI-treated leaves the expression of those genes was significantly lower than in untreated control samples.These results suggest that the prompt stomatal closure through the regulation of ABA 8'-hydroxylase may be required for the plants to survive under relatively long drought conditions.