Key Laboratory of Forest Genetics & Biotechnology of Ministry of Education, Nanjing Forestry University, Nanjing, Jiangsu, 210037, China; Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu, 210037, China.
Plant Physiol Biochem. 2022 Nov 1;190:1-10. doi: 10.1016/j.plaphy.2022.08.020. Epub 2022 Aug 28.
Strigolactones (SLs) play prominent roles in regulating shoot branching and root architecture in model plants. However, their roles in non-model (particularly woody) plants remain unclear. Liriodendron chinense is a timber tree species widely planted in southern China. The outturn percentage and wood quality of L. chinense are greatly affected by the branching characteristics of its shoot, and the rooting ability of the cuttings is key for its vegetative propagation. Here, we isolated and analyzed the function of the MORE AXILLARY GROWTH 1 (LcMAX1) gene, which is involved in L. chinense SL biosynthesis. RT-qPCR showed that LcMAX1 was highly expressed in the roots and axillary buds. LcMAX1 was located in the endoplasmic reticulum (ER) and nucleus. LcMAX1 ectopic expression promoted primary root growth, whereas there were no phenotypic differences in shoot branching between transgenic and wild-type (WT) A. thaliana plants. LcMAX1 overexpression in the max1 mutant restored them to the WT A. thaliana phenotypes. Additionally, AtPIN1, AtPIN2, and AtBRC1 expressions were significantly upregulated in transgenic A. thaliana and the max1 mutant. It was therefore speculated that LcMAX1 promotes primary root growth by regulating expression of auxin transport-related genes in A. thaliana, and LcMAX1 inhibits shoot branching by upregulating expression of AtBRC1 in the max1 mutant. Altogether, these results demonstrated that the root development and shoot branching functions of LcMAX1 were similar to those of AtMAX1. Our findings provide a foundation for obtaining further insights into root and branch development in L. chinense.
独脚金内酯（SLs）在调节模式植物的分枝和根系结构方面起着重要作用。然而，它们在非模式（特别是木本）植物中的作用尚不清楚。鹅掌楸是一种广泛种植在中国南方的用材树种。鹅掌楸的出材率和木材质量受其枝条分枝特性的影响很大，插条的生根能力是其营养繁殖的关键。本研究中，我们分离并分析了参与鹅掌楸 SL 生物合成的 MORE AXILLARY GROWTH 1（LcMAX1）基因的功能。RT-qPCR 结果显示，LcMAX1 在根和腋芽中表达量较高。LcMAX1 定位于内质网（ER）和细胞核。LcMAX1 异位表达促进了主根的生长，而转基因和野生型（WT）拟南芥植物的分枝表型没有差异。在 max1 突变体中过表达 LcMAX1 使其恢复到 WT 拟南芥表型。此外，在转基因拟南芥和 max1 突变体中，AtPIN1、AtPIN2 和 AtBRC1 的表达明显上调。因此，推测 LcMAX1 通过调节拟南芥中生长素运输相关基因的表达来促进主根的生长，而在 max1 突变体中通过上调 AtBRC1 的表达来抑制分枝。总之，这些结果表明 LcMAX1 的根发育和分枝功能与 AtMAX1 相似。本研究结果为进一步了解鹅掌楸的根和枝发育提供了基础。
