Abstract

Most land plant species have the ability to establish a symbiosis with arbuscular mycorrhizal (AM) fungi. These fungi penetrate into root cortical cells and form branched structures (known as arbuscules) for nutrient exchange. We cloned the MdIAA24 from apple (Malus domestica) following its up-regulation during AM symbiosis. Results demonstrate the positive impact of the overexpression (OE) of MdIAA24 in apple on AM colonization. We observed the strigolactone (SL) synthesis genes, including MdD27, MdCCD7, MdCCD8a, MdCCD8b and MdMAXa, to be up-regulated in the OE lines. Thus, the OE lines exhibited both a higher SL content and colonization rate. Furthermore, we observed that the OE lines were able to maintain better growth parameters under AM inoculation conditions. Under drought stress with the AM inoculation, the OE lines were less damaged, which was demonstrated by a higher relative water content, a lower relative electrolytic leakage, a greater osmotic adjustment, a higher reactive oxygen species scavenging ability, an improved gas exchange capacity and an increased chlorophyll fluorescence performance. Our findings demonstrate that the OE of MdIAA24 in apple positively regulates the synthesis of SL and the formation of arbuscules as a drought stress coping mechanism.

中文翻译：

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MdIAA24的过表达通过积极调节strigolactone生物合成和菌根，提高了苹果的抗旱性。

摘要

大多数陆地植物物种都具有与丛枝菌根（AM）真菌共生的能力。这些真菌渗透到根皮层细胞中，并形成分支结构（称为丛枝）以进行营养交换。我们在苹果共生期间上调了MdIAA24，从苹果（Malus domestica）中克隆了它。结果表明，苹果中MdIAA24的过表达（OE）对AM定植具有积极影响。我们观察到了strigolactone（SL）合成基因，包括MdD27，MdCCD7，MdCCD8a，MdCCD8b和MdMAXa，将在OE行中上调。因此，OE系显示出更高的SL含量和定殖率。此外，我们观察到在AM接种条件下OE品系能够保持更好的生长参数。在AM接种的干旱胁迫下，OE系受到的损害较小，这表现为较高的相对含水量，较低的相对电解泄漏，较大的渗透调节，较高的活性氧清除能力，改进的气体交换能力和叶绿素荧光性能增强。我们的发现表明，MdIAA24在苹果中的OE调控干旱胁迫应对机制，正调控SL的合成和丛枝的形成。