Abstract
Tea plant (Camellia sinensis (L.) O. Kuntze) is one of the most important economic crops with multiple mutants. Recently, we found a special tea germplasm that has an aberrant tissue on its branches. To figure out whether this aberrant tissue is associated with floral bud (FB) or dormant bud (DB), we performed tissue section, transcriptome sequencing, and metabolomic analysis of these tissues. Longitudinal sections indicated the aberrant tissue internal structure was more like a special bud (SB), but was similar to that of DB. Transcriptome data analysis showed that the number of heterozygous and homozygous SNPs was significantly different in the aberrant tissue compared with FB and DB. Further, by aligning the unmapped sequences of the aberrant tissue to the Non-Redundant Protein Sequences (NR) database, we observed that 36.13% of unmapped sequences were insect sequences, which suggested that the aberrant tissue might be a variation of dormant bud tissue influenced by the interaction of tea plants and insects or pathogens. Metabolomic analysis showed that the differentially expressed metabolites (DEMs) between the aberrant tissue and DB were significantly enriched in the metabolic pathways of biosynthesis of plant hormones and biosynthesis of phenylpropanoids. Subsequently, we analyzed the differentially expressed genes (DEGs) in the above mentioned two tissues, and the results indicated that photosynthetic capacity in the aberrant tissue was reduced, whereas the ethylene, salicylic acid and jasmonic acid signaling pathways were activated. We speculated that exogenous infection induced programmed cell death (PCD) and increased the lignin content in dormant buds of tea plants, leading to the formation of this aberrant tissue. This study advanced our understanding of the interaction between plants and insects or pathogens, providing important clues about biotic stress factors and key genes that lead to mutations and formation of the aberrant tissue.
Highlights
Tea is a traditional beverage that has been consumed for thousands of years in China
We initially assumed that the structural features of special bud (SB) tissues combine the characteristics of floral bud (FB) and dormant bud (DB) represent a combination of the characteristics of FB and DB (Figures 1B,C)
The longitudinal sections showed that FB and DB had typical internal structures
Summary
Tea is a traditional beverage that has been consumed for thousands of years in China. In terms of external morphological characteristics, the aberrant tissue appears to combine the characteristics of FB and DB of tea plants. We found that the morphological features of the popular “Yabao tea” in the tea market are similar to the aberrant tissue (Supplementary Figure 1D). It was reported that the vast majority of the raw materials of “Yabao tea” did not come from tea plants (Xin, 2013), this raises very interesting and important questions: What is this aberrant tissue and why does it appear on tea plants (C. sinensis (L.) O. Gall development can be divided into four processes, including secretion of signaling molecules from insects, perception of the signals by plants, plant cell regeneration and differentiation, and organization of gall tissue (Giron et al, 2016). The molecular mechanism of gall development is still unclear
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