Arbuscular Mycorrhizal Fungus Alters Root System Architecture in Camellia sinensis L. as Revealed by RNA-Seq Analysis

Abstract

Arbuscular mycorrhizal fungus (AMF), forming symbiosis with most terrestrial plants, strongly modulates root system architecture (RSA), which is the main characteristic of root in soil, to improve plant growth and development. So far, the studies of AMF on tea plant seedlings are few and the relevant molecular mechanism is not deciphered. In this study, the 6-month-old cutting seedlings of tea plant cultivar “Wancha No.4” were inoculated with an AMF isolate, Rhizophagus intraradices BGC JX04B and harvested after 6 months of growth. The indexes of RSA and sugar contents in root were determined. The transcriptome data in root tips of mycorrhizal and non-mycorrhizal cutting seedlings were obtained by RNA-sequence (Seq) analysis. The results showed that AMF significantly decreased plant growth, but increased the sucrose content in root and the higher classes of lateral root (LR) formation (third and fourth LR). We identified 2047 differentially expressed genes (DEGs) based on the transcriptome data, and DEGs involved in metabolisms of phosphorus (42 DEGs), sugar (39), lipid (67), and plant hormones (39) were excavated out. Variation partitioning analysis showed all these four categories modulated the RSA. In phosphorus (P) metabolism, the phosphate transport and release (DEGs related to purple acid phosphatase) were promoted by AMF inoculation, while DEGs of sugar transport protein in sugar metabolism were downregulated. Lipid metabolism might not be responsible for root branching but for AMF propagation. With respect to phytohormones, DEGs of auxin (13), ethylene (14), and abscisic acid (5) were extensively affected by AMF inoculation, especially for auxin and ethylene. The further partial least squares structural equation modeling analysis indicated that pathways of P metabolism and auxin, as well as the direct way of AMF inoculation, were of the most important in AMF promoting root branching, while ethylene performed a negative role. Overall, our data revealed the alterations of genome-wide gene expression in tea plant roots after inoculation with AMF and provided a molecular basis for the regulatory mechanism of RSA (mainly root branching) changes induced by AMF.

Commercial Bioinoculants Increase Root Length Colonization and Improve Petiole Nutrient Concentration of Field-grown Grapevines

“…The prevalence of significant positive correlations between RD, RL, SRL, specifically with products 4 and 2 (Table 7), corroborate these effects and reveal that AMF colonization alone (for product 2, which contained only an inorganic carrier of clay) affected grapevine plasticity by inducing morphological changes in the root system. Our results are consistent with those of previous studies that focused on AMF effects on grapevines and other crops (Agu ın et al 2004;Chen et al 2021), indicating that roots of AMF-inoculated plants can improve their ability to absorb and use nutrients and water in the soil under different environmental stresses (Comas et al 2013;McCormack and Iversen 2019).…”

“…Root colonization by AMF also affects root characteristics of host plants (Chen et al 2021); however, there is limited information about how AMF affects diverse traits of grapevine root morphology (Agu ın et al 2004). These changes may alter the morphology of the root system in a structural, quantitative, spatial, and temporal manner (Kapoor et al 2008), but impacts seem to vary according to specific plant-fungal combinations and environment (Holland et al 2018).…”

Arbuscular mycorrhizal fungus alleviates anthracnose disease in tea seedlings

“…Another aliquot of extracted RNA was used for the quantitative real-time PCR (qRT-PCR) to validate the RNA-seq results according to a previous protocol ( Chen et al., 2021 ). With the extracted RNA as template, cDNA was synthesized using iScriptTM cDNA Synthesis Kit (Bio-Rad, USA).…”

“…The growth substrate (1-kg substrate in each pot) was a mixture of autoclaved (121°C, 2 h) soils and peat (1:1, v:v). As described in the paper of Chen et al (2021), the soils were collected from the tea plant garden of the Tea Research Institute, Anhui Academy of Agricultural Sciences, Huangshan, China (29°41'18"E, 118°15'33"N), and the soil chemical properties were determined as follows: pH 5.13, organic matter content 5.17 g•kg −1 , available N 31.40 mg•kg −1 , available P 2.52 mg•kg −1 , and available K 76.20 mg•kg −1 . The substrate was additionally applied with 200 mg•kg −1 N [(NH 4 ) 2 SO 4 ], 100 mg•kg −1 K (KNO 3 ), and 50 mg•kg −1 P (KH 2 PO 4 ).…”

Comparative transcriptome analysis of molecular mechanisms underlying adventitious root developments in Huangshan Bitter tea (Camellia gymnogyna Chang) under red light quality

“…Tea is the most widely consumed non-alcoholic beverage in the world ( Chen et al., 2021 ), which offers a plethora of health benefits such as anti-oxidant, anti-cancer, anti-cardiovascular disease, anti-allergic activities and even memory improvement ( Brickman et al., 2014 ; Yu et al., 2020 ). Huangshan Bitter tea ( Camellia gymnogyna Chang ) is a precious ancient tea plant discovered in 2021 at Yibin City, Sichuan Province, China.…”