Genome-wide identification of tea plant (Camellia sinensis) BAHD acyltransferases reveals their role in response to herbivorous pests

Abstract

Background: BAHD acyltransferases are among the largest metabolic protein domain families in the genomes of terrestrial plants and play important roles in plant growth and development, aroma formation, and biotic and abiotic stress responses. Little is known about the BAHDs in the tea plant, a cash crop rich in secondary metabolites.

Results: In this study, 112 BAHD genes (CsBAHD01-CsBAHD112) were identified from the tea plant genome, with 85% (98/112) unevenly distributed across the 15 chromosomes. The number of BAHD gene family members has significantly expanded from wild tea plants to the assamica type to the sinensis type. Phylogenetic analysis showed that they could be classified into seven subgroups. Promoter cis-acting element analysis revealed that they contain a large number of light, phytohormones, and stress-responsive elements. Many members displayed tissue-specific expression patterns. CsBAHD05 was expressed at more than 500-fold higher levels in purple tea leaves than in green tea leaves. The genes exhibiting the most significant response to MeJA treatment and feeding by herbivorous pests were primarily concentrated in subgroups 5 and 6. The expression of 23 members of these two subgroups at different time points after feeding by tea green leafhoppers and tea geometrids was examined via qPCR, and the results revealed that the expression of CsBAHD93, CsBAHD94 and CsBAHD95 was significantly induced after the tea plants were subjected to feeding by both pricking and chewing pests. Moreover, based on the transcriptome data for tea plants being fed on by these two pests, a transcriptional regulatory network of different transcription factor genes coexpressed with these 23 members was constructed.

Conclusions: Our study provides new insights into the role of BAHDs in the defense response of tea plants, and will facilitate in-depth studies of the molecular function of BAHDs in resistance to herbivorous pests.

Keywords: Camellia sinensis; Acyltransferase; HIPVs; Tea geometrid; Tea green leafhopper.

Fig. 1

Collinearity of CsBAHD gene pairs. (A) Collinearity analysis of the CsBAHD gene family. The identified CsBAHD gene pairs are connected by red lines. (B) and (C) Collinearity analysis of CsBAHD genes between SCZ and LJ43, SCZ and TGY, SCZ and YK10, and SCZ and DASZ. The collinear gene pairs are connected by red lines, and their details are shown in Table S3

Fig. 2

Phylogenetic analysis of the BAHD genes in tea plants and other plants. The accession numbers of the other plant BAHD proteins used for the evolutionary tree construction are listed in Table S4

Fig. 3

Phylogenetic tree, gene structure and conserved motifs of CsBAHDs

Fig. 4

Statistics for the light responsive, hormone responsive and stress-related cis-regulatory elements identified in the promoter regions of the CsBAHD genes

Fig. 5

The expression patterns of CsBAHDs in tea plants based on public transcriptome data. (A) The expression patterns of CsBAHDs in eight different tissues of tea plants. The numbers on the phylogenetic tree represent the seven subgroups in Fig. 2. (B) The expression patterns of CsBAHDs in tea leaves from five different months. (C) The expression patterns of CsBAHDs in green and purple tea leaves. (D) The expression patterns of CsBAHDs in tea plants under cold acclimation. (E) The expression patterns of CsBAHDs in tea plants at different time points after MeJA treatment. (F) The expression patterns of CsBAHDs in tea plants at different time points after feeding by tea green leafhoppers

Fig. 6

The relative expression levels of the CsBAHDs in tea leaves at different time points after feeding by tea green leafhoppers. M6, M24, and M48 represent samples taken 6, 24,48 h after feeding, while CK6, CK24, and CK48 represent control samples at the corresponding time points. The expression levels were calculated based on the 2^−ΔCT method relative to the internal reference gene. The bars represent the mean ± SD (n = 3). Significant differences between the treatments and CK were determined by Student’s t test (*p < 0.05, **p < 0.01, ns: no significant difference)

Fig. 7

The relative expression levels of the CsBAHDs in tea leaves at different time points after feeding by tea geometrids. E3, E6, E9, E12, and E24 represent samples taken 3, 6, 9, 12, and 24 h after feeding, while CK3, CK6, CK9, CK12, and CK24 represent control samples at the corresponding time points. The expression levels were calculated based on the 2^−ΔCT method relative to the internal reference gene. The bars represent the mean ± SD (n = 3). Significant differences between the treatments and CK were determined by Student’s t test (*p < 0.05, **p < 0.01, ns: no significant difference)

Fig. 8

Transcriptional regulation of CsBAHD genes in response to feeding by herbivorous pests. The correlations between the expression of CsBAHD genes and that of different transcription factors are shown with colored lines (Pearson’s correlation test, P ≤ 0.01). The gene correlation expression networks were visualized using Cytoscape v3.7.1 software. The detailed expression correlations used for network construction are listed in Table S6