Chen Weili, Shan Wenshu, Niu Tingting, Ye Tao, Sun Qinyu, Zhang Jiaxia
Tea Research Institute, Anhui Academy of Agricultural Sciences, Huangshan, China.
Front Plant Sci. 2023 Sep 18;14:1258410. doi: 10.3389/fpls.2023.1258410. eCollection 2023.
Adventitious root (AR) development, affected by various biotic and abiotic factors, is the most important procedure in tea plant ( L.) cutting propagation. Establishing symbiotic relationships with most terrestrial plants, AMF (Arbuscular mycorrhizal fungus) can mediate the AR formation of several herbaceous and woody plants in previous studies.
In this paper, effects of combined application of AMF and exogenous auxin on AR formation of cuttings from different tea plant varieties ('Pingyangtezao', 'Longjing 43' and 'Longjingchangye') were studied. Then we also performed RNA-Seq analysis with 'Pingyangtezao' cuttings aiming to find the possible auxin-related pathway of AM fungal regulation on AR formation. To accurately uncover the regulatory mechanism of AMF on AR formation of tea cuttings, rooting process were separated into four stages (S0, non-rooting; S1, AR protrusion; S2, AR formation and S3, AR elongation) at the same sampling time.
Results showed that IBA treatment increased the mycorrhizal colonization rate, especially in 'Pingyangtezao' variety (from 37.58% to 46.29%). Both inoculating AMF and addition of IBA promoted the AR formation, and rooting of different tea plant varieties showed different dependence on auxin. AMF could alleviate the effect of auxin-related inhibitors (2,3,5-triiodobenzoic acid, L-α-(Aminooxy)-β-phenylpropionic acid and α-(phenylethyl-2-oxo)-IAA) on rooting of tea cuttings, even though the colonization of AMF was hindered at various degrees. Transcriptomic analysis showed that different numbers of differentially expressed genes (DEGs) at various rooting stages of tea cuttings with the most at S2 stage (1360 DEGs), indicating the increasing regulation by AMF with the development of AR. Similar trend was found in auxin-related DEGs, and family genes of , , , , , , and involved in the AM fungal regulation on AR formation of tea cuttings. Additionally, AMF strongly mediated auxin transport and signal transduction pathways in tea cuttings as showed by the results of correlation analysis. Overall, interaction of AMF and exogenous auxin in promoting rooting and the preliminary mechanism of AMF regulating AR formation of tea cuttings was deciphered in this paper, which may provide a basis for further deep mechanistic research and cutting propagation of tea production.
不定根（AR）发育受多种生物和非生物因素影响，是茶树扦插繁殖中最重要的过程。丛枝菌根真菌（AMF）与大多数陆生植物建立共生关系，在先前的研究中，它可以介导几种草本和木本植物的不定根形成。
本文研究了AMF与外源生长素联合应用对不同茶树品种（‘平阳特早’、‘龙井43’和‘龙井长叶’）插条不定根形成的影响。然后，我们对‘平阳特早’插条进行了RNA测序分析，旨在寻找AM真菌调控不定根形成可能的生长素相关途径。为了准确揭示AMF对茶树插条不定根形成的调控机制，在同一采样时间将生根过程分为四个阶段（S0，未生根；S1，不定根突出；S2，不定根形成；S3，不定根伸长）。
结果表明，吲哚丁酸（IBA）处理提高了菌根定殖率，尤其是在‘平阳特早’品种中（从37.58%提高到46.29%）。接种AMF和添加IBA均促进了不定根形成，不同茶树品种的生根对生长素表现出不同的依赖性。AMF可以减轻生长素相关抑制剂（2,3,5-三碘苯甲酸、L-α-（氨基氧基）-β-苯丙酸和α-（苯乙基-2-氧代）-吲哚乙酸）对茶树插条生根的影响，尽管AMF的定殖在不同程度上受到了阻碍。转录组分析表明，茶树插条在不同生根阶段有不同数量的差异表达基因（DEGs），其中S2阶段最多（1360个DEGs），表明随着不定根的发育，AMF的调控作用增强。在生长素相关的DEGs中也发现了类似的趋势，以及参与AM真菌调控茶树插条不定根形成的、、、、、、和家族基因。此外，相关性分析结果表明，AMF强烈介导了茶树插条中的生长素运输和信号转导途径。总体而言，本文解析了AMF与外源生长素在促进生根方面的相互作用以及AMF调控茶树插条不定根形成的初步机制，这可能为进一步深入的机制研究和茶叶生产中的扦插繁殖提供依据。
