Chen Weili, Niu Tingting, Lian Wenxu, Ye Tao, Sun Qinyu, Zhang Jiaxia
Tea Research Institute, Anhui Academy of Agricultural Sciences, Huangshan, 245000, China.
BMC Plant Biol. 2024 Dec 27;24(1):1266. doi: 10.1186/s12870-024-05955-z.
Adventitious root (AR) formation is the key step for successful cutting propagation of tea plants (Camellia sinensis L.). Studies showed that arbuscular mycorrhizal fungus (AMF) can promote the rooting ability, and auxin pathway in basal stem of cuttings was involved in this process. However, auxin and abscisic acid (another important regulator on AR formation) in the other parts of cuttings at different rooting stages responding to AMF inoculation are not well studied. Therefore, in this paper, contents, enzymes and genes related to these two plant hormones were comprehensively determined aiming to unveil how endogenous indole-3-acetic acid (IAA) and abscisic acid (ABA) involve in the AMF regulating AR development of tea cuttings.
Inoculating with AMF significantly increased the proportion of cuttings at S2 stage (AR formation), which was more than twice as much as the control. And the total rooting rate in mycorrhizal treatment was also higher than that in the control with an increase of 8.66%. Enzyme activity assays showed that except for decreased polyphenol oxidase (PPO) activity at the S3 stage and peroxidase (POD) activity in middle stem of S3 stage, AMF inoculation increased activities of POD, PPO, superoxide dismutase (SOD) and catalase (CAT) to varying degrees in leaf, middle stem and basal stem of tea cuttings. After inoculation with AMF, the indoleacetic acid oxidase (IAAO) activity decreased to a certain extent in the first three stages of tea cuttings, which showed a trend of 'low-high-low' in the basal stem of all treatments. Besides, there was a significantly positive correlation between SOD activity and AR formation, especially for the proportion of cuttings at S2 and S3 stages. Higher IAA level and IAA/ABA ratio was found in basal stem of cuttings at S1 stage induced by AMF, which promoting the AR formation as revealed by correlation analysis. At the same time, AMF significantly elevated the level of IAA in leaf at S1 stage. By screening differentially expressed genes (DEGs) related to IAA and ABA pathways, together with redundant analysis, it was indicated that auxin biosynthesis and transport, as well as ABA transport and signal transduction, were involved in AMF regulating the rooting of tea cuttings.
Overall, both endogenous IAA and ABA played roles in the regulation of AR formation of tea cuttings by AMF inoculating, enriching the theoretical basis of AMF regulating rooting of cuttings and providing foundations for cutting propagation of tea plants.
不定根（AR）形成是茶树（Camellia sinensis L.）扦插繁殖成功的关键步骤。研究表明，丛枝菌根真菌（AMF）能促进生根能力，且插穗基部茎中的生长素途径参与了这一过程。然而，不同生根阶段插穗其他部位的生长素和脱落酸（另一种对AR形成的重要调节因子）对AMF接种的响应尚未得到充分研究。因此，本文综合测定了与这两种植物激素相关的含量、酶和基因，旨在揭示内源性吲哚 - 3 - 乙酸（IAA）和脱落酸（ABA）如何参与AMF调节茶树插穗的AR发育。
接种AMF显著提高了S2阶段（AR形成阶段）插穗的比例，比对照高出两倍多。菌根处理的总生根率也高于对照，提高了8.66%。酶活性测定表明，除S3阶段多酚氧化酶（PPO）活性降低以及S3阶段中间茎中过氧化物酶（POD）活性降低外，接种AMF使茶树插穗叶片、中间茎和基部茎中的POD、PPO、超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性不同程度增加。接种AMF后，茶树插穗前三个阶段的吲哚乙酸氧化酶（IAAO）活性有一定程度降低，在所有处理的基部茎中呈“低 - 高 - 低”趋势。此外，SOD活性与AR形成之间存在显著正相关，尤其是S2和S3阶段插穗的比例。AMF诱导的S1阶段插穗基部茎中IAA水平和IAA/ABA比值较高，相关性分析表明这促进了AR形成。同时，AMF显著提高了S1阶段叶片中IAA的水平。通过筛选与IAA和ABA途径相关的差异表达基因（DEG），并结合冗余分析表明，生长素生物合成和运输以及ABA运输和信号转导参与了AMF调节茶树插穗生根。
总体而言，内源性IAA和ABA在AMF接种调节茶树插穗AR形成中均发挥作用，丰富了AMF调节插穗生根的理论基础，并为茶树扦插繁殖提供了依据。
