State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A & F University, No.3 Taicheng Road, Yangling 712100 Shaanxi, China.
Tree Physiol. 2021 Jan 9;41(1):134-146. doi: 10.1093/treephys/tpaa109.
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.
大多数陆地植物物种都有能力与丛枝菌根（AM）真菌建立共生关系。这些真菌穿透根皮层细胞，并形成分支结构（称为丛枝）进行养分交换。我们从苹果（Malus domestica）中克隆了 MdIAA24，它在 AM 共生过程中被上调。结果表明，MdIAA24 在苹果中的过表达（OE）对 AM 定殖有积极影响。我们观察到 Strigolactone（SL）合成基因，包括 MdD27、MdCCD7、MdCCD8a、MdCCD8b 和 MdMAXa，在 OE 系中上调。因此，OE 系表现出更高的 SL 含量和定殖率。此外，我们观察到在 AM 接种条件下，OE 系能够更好地维持生长参数。在 AM 接种的干旱胁迫下，OE 系受到的损伤较小，这表现为相对含水量较高、相对电导率较低、渗透调节能力较强、活性氧清除能力较强、气体交换能力提高和叶绿素荧光性能增强。我们的研究结果表明，在苹果中过表达 MdIAA24 可以正向调节 SL 的合成和丛枝的形成，作为一种应对干旱胁迫的机制。
