Uddin Saleem, Munir Muhammad Zeeshan, Larriba Eduardo, Pérez-Pérez José Manuel, Gull Sadia, Pervaiz Tariq, Mahmood Umer, Mahmood Zahid, Sun Yuhan, Li Yun
State Key Laboratory of Tree Genetics and Breeding, Engineering Technology Research Center of Black Locust of National Forestry and Grassland Administration, National Engineering Research Center of Tree Breeding and Ecological Restoration, College of Biological Sciences and Technology, Beijing Forestry University, Beijing, 100083, People's Republic of China.
College of Horticulture and Landscape Architecture, Southwest University, Chongqing, 400716, China.
Planta. 2024 Feb 8;259(3):66. doi: 10.1007/s00425-024-04341-1.
Optimal levels of indole-3-butyric acid (IBA) applied at the stem base promote adventitious root (AR) initiation and primordia formation, thus promoting the rooting of leafy micro-cuttings of tetraploid Robinia pseudoacacia. Tetraploid Robinia pseudoacacia L. is a widely cultivated tree in most regions of China that has a hard-rooting capability, propagated by stem cuttings. This study utilizes histological, physiological, and transcriptomic approaches to explore how root primordia are induced after indole butyric acid (IBA) treatment of micro-cuttings. IBA application promoted cell divisions in some cells within the vasculature, showing subcellular features associated with adventitious root (AR) founder cells. The anatomical structure explicitly showed that AR initiated from the cambium layer and instigate the inducible development of AR primordia. Meanwhile, the hormone data showed that similar to that of indole-3-acetic acid, the contents of trans-zeatin and abscisic acid peaked at early stages of AR formation and increased gradually in primordia formation across the subsequent stages, suggesting their indispensable roles in AR induction. On the contrary, 24-epibrassinolide roughly maintained at extremely high levels during primordium initiation thoroughly, indicating its presence was involved in cell-specific reorganization during AR development. Furthermore, antioxidant activities transiently increased in the basal region of micro-cuttings and may serve as biochemical indicators for distinct rooting phases, potentially aiding in AR formation. Transcriptomic analysis during the early stages of root formation shows significant downregulation of the abscisic acid and jasmonate signaling pathways, while ethylene and cytokinin signaling seems upregulated. Network analysis of genes involved in carbon metabolism and photosynthesis indicates that the basal region of the micro-cuttings undergoes rapid reprogramming, which results in the breakdown of sugars into pyruvate. This pyruvate is then utilized to fuel the tricarboxylic acid cycle, thereby sustaining growth through aerobic respiration. Collectively, our findings provide a time-course morphophysiological dissection and also suggest the regulatory role of a conserved auxin module in AR development in these species.
在茎基部施加最佳水平的吲哚 - 3 - 丁酸（IBA）可促进不定根（AR）的起始和原基形成，从而促进四倍体刺槐带叶微插条的生根。四倍体刺槐是中国大部分地区广泛种植的一种树木，具有难生根的特性，通常通过茎插条进行繁殖。本研究利用组织学、生理学和转录组学方法，探究吲哚丁酸（IBA）处理微插条后根原基是如何被诱导的。施加IBA促进了维管系统内一些细胞的细胞分裂，显示出与不定根（AR）起始细胞相关的亚细胞特征。解剖结构明确显示，不定根从形成层开始，并促使不定根原基的诱导发育。同时，激素数据表明，与吲哚 - 3 - 乙酸类似，反式玉米素和脱落酸的含量在不定根形成的早期阶段达到峰值，并在随后阶段的原基形成过程中逐渐增加，表明它们在不定根诱导中发挥着不可或缺的作用。相反，24 - 表油菜素内酯在原基起始过程中总体上大致维持在极高水平，表明其存在参与了不定根发育过程中的细胞特异性重组。此外，微插条基部区域的抗氧化活性短暂增加，可能作为不同生根阶段的生化指标，潜在地有助于不定根的形成。根形成早期阶段的转录组分析表明，脱落酸和茉莉酸信号通路显著下调，而乙烯和细胞分裂素信号似乎上调。对参与碳代谢和光合作用的基因进行网络分析表明，微插条的基部区域经历了快速重编程，导致糖类分解为丙酮酸。然后利用该丙酮酸为三羧酸循环提供能量，从而通过有氧呼吸维持生长。总的来说，我们的研究结果提供了一个时间进程的形态生理剖析，并表明了一个保守的生长素模块在这些物种不定根发育中的调控作用。
