The Role of Root Tissue Membrane Proteins in Replanting Stress in Rehmannia glutinosa

The perennial herbaceous plant, Rehmannia glutinosa Libosch, is one of traditional Chinese medicines with a long history of cultivation and medicinal use. However, in production of R. glutinosa, replanting disease severely affected its yield and medicinal quality. Replanting disease is the special stress including biotic and abiotic factors. The membrane proteins system plays the important role in process of plants responding to stress factors. In this study, the differentially expressed root tissue membrane proteins between first planted and replanted R. glutinosa were identified through the isobaric tag for relative and absolute quantitation (iTRAQ). As a result, the membrane protein extraction kit could highly effectively extract the membrane proteins from R. glutinosa root tissue. A total of 698 differential membrane proteins between first planted and replanted R. glutinosa were obtained. Functional analysis revealed that the differential membrane proteins were involved in various metabolic pathways, including transport and breakdown, signal transduction, membrane trafficking and environmental response. Two important molecular events that occurred in cellular membrane of replanted R. glutinosa including the imbalance of ROS (Reactive Oxygen Species) metabolism and immune response were identified in this study. When replanted R. glutinosa plants faced the complex environment factors in rhizosphere, the proteins located in cellular membrane were often first activated to response to stress stimulus, resulted in the upregulated expression of a large number of LRR-RLKs (Leucine-rich repeat receptor-like kinases) receptor proteins. Meanwhile, the Ca2+ signal proteins and related receptor proteins transmitted and responded to the replanting stress, which induced severe oxidative stress response in the cell membrane of R. glutinosa, membrane peroxidation, intracellular signal disorder, and eventually produce replanting disease. Our findings provided the theoretical and data foundation for elucidating the key mechanisms associated with replanting stress. © 2021 Friends Science Publishers

Bio-Fertilizer Amendment Alleviates The Replanting Disease By Reshaping Leaf And Root Microbiome

A growing problem in intensive agricultural systems is replanting disease. Application of bio-fertilizer containing beneficial microbes contributes to disease suppression and is a promising strategy to control replanting disease. However, the effect of both replanting disease and bio-fertilizer amendment on the assembly of crop microbiota in leaves and roots and their relationships to crop yield and quality remains elusive. In these experiments, roots and leaves of Radix pseudostellariae were collected from different consecutive monoculture and bio-fertilizer amended fields and characterized the associated microbiota by bacterial 16S rRNA gene sequencing and qRT-PCR. Consecutive monoculture altered the bacterial community structure and composition and significantly increased the abundance of pathogenic Ralstonia and Fusarium oxysporum in leaves and roots. Furthermore, bio-fertilizer application alleviated replanting disease by decreasing the pathogen load, increasing the beneficial genera Pseudomonas, Streptomyces, Paenibacillus, and Bradyrhizobium, and enhancing positive connections of the bacterial community across the two compartments. Bio-fertilizer had a positive and indirect effect as indicated by a structural equation models on both yield and quality by shaping the leaf microbiota rather than the root microbiota. Our findings highlight the role of leaf and root microbiota on replanting disease, showing that bio-fertilizer contributes to alleviating replanting disease by improving the plant-microbe interactions.

RgC3H Involves in the Biosynthesis of Allelopathic Phenolic Acids and Alters Their Release Amount in Rehmannia glutinosa Roots

Rehmannia glutinosa production is affected by replanting disease, in which autotoxic harm to plants is mediated by endogenous phenolic acids as allelopathic compounds found in root exudates. These phenolic acids are mostly phenylpropanoid products of plants’ secondary metabolisms. The molecular mechanism of their biosynthesis and release has not been explored in R. glutinosa. P-coumarate-3-hydroxylase (C3H) is the second hydroxylase gene involved in the phenolic acid/phenylpropanoid biosynthesis pathways. C3Hs have been functionally characterized in several plants. However, limited information is available on the C3H gene in R. glutinosa. Here, we identified a putative RgC3H gene and predicted its potential function by in silico analysis and subcellular localization. Overexpression or repression of RgC3H in the transgenic R. glutinosa roots indicated that the gene was involved in allelopathic phenolic biosynthesis. Moreover, we found that these phenolic acid release amount of the transgenic R. glutinosa roots were altered, implying that RgC3H positively promotes their release via the molecular networks of the activated phenolic acid/phenylpropanoid pathways. This study revealed that RgC3H plays roles in the biosynthesis and release of allelopathic phenolic acids in R. glutinosa roots, laying a basis for further clarifying the molecular mechanism of the replanting disease development.