Genome-wide identification, and phylogenetic and expression profiling analyses, of XTH gene families in Brassica rapa L. and Brassica oleracea L

Identification and expression analysis of the Xyloglucan transglycosylase/hydrolase (XTH) gene family under abiotic stress in oilseed (Brassica napus L.)

XTH genes are key genes that regulate the hydrolysis and recombination of XG components and plays role in the structure and composition of plant cell walls. Therefore, clarifying the changes that occur in XTHs during plant defense against abiotic stresses is informative for the study of the plant stress regulatory mechanism mediated by plant cell wall signals. XTH proteins in Arabidopsis thaliana was selected as the seed sequences in combination with its protein structural domains, 80 members of the BnXTH gene family were jointly identified from the whole genome of the Brassica napus ZS11, and analyzed for their encoded protein physicochemical properties, phylogenetic relationships, covariance relationships, and interoperating miRNAs. Based on the transcriptome data, the expression patterns of BnXTHs were analyzed in response to different abiotic stress treatments. The relative expression levels of some BnXTH genes under Al, alkali, salt, and drought treatments after 0, 6, 12 and 24 h were analyzed by using qRT-PCR to explore their roles in abiotic stress tolerance in B. napus. BnXTHs showed different expression patterns in response to different abiotic stress signals, indicating that the response mechanisms of oilseed rape against different abiotic stresses are also different. This paper provides a theoretical basis for clarifying the function and molecular genetic mechanism of the BnXTH gene family in abiotic stress tolerance in rapeseed.

Argon non-thermal plasma treatment promotes the development of rice (Oryza sativa L.) in saline alkali environments

Soil salinization leads to a reduction in arable land area, which seriously endangers food security. Developing saline-alkali land has become a key measure to address the contradiction between population growth and limited arable land. Rice is the most important global food crop, feeding half of the world's population and making it a suitable choice for planting on saline-alkali lands. The traditional salt-alkali improvement method has several drawbacks. Currently, non-thermal plasma (NTP) technology is being increasingly applied in agriculture. However, there are few reports on the cultivation of salt/alkali-tolerant rice. Under alkaline stress, argon NTP treatment significantly increased the germination rate of Longdao 5 (LD5) rice seeds. In addition, at 15 kV and 120 s, NTP treatment significantly increased the activity of antioxidant enzymes such as catalase and SOD. NTP treatment induced changes in genes related to salt-alkali stress in rice seedlings, such as chitinase and xylanase inhibitor proteins, which increased the tolerance of the seeds to salt-alkali stress. This experiment has expanded the application scope of NTP in agriculture, providing a more cost-effective, less harmful, and faster method for developing salt-alkali-tolerant rice and laying a theoretical foundation for cultivating NTP-enhanced salt-alkali-tolerant rice.

Genome-Wide Analysis of the Xyloglucan Endotransglucosylase/Hydrolase (XTH) Gene Family: Expression Pattern during Magnesium Stress Treatment in the Mulberry Plant (Morus alba L.) Leaves

Mulberry (Morus alba L.), a significant fruit tree crop, requires magnesium (Mg) for its optimal growth and productivity. Nonetheless, our understanding of the molecular basis underlying magnesium stress tolerance in mulberry plants remains unexplored. In our previous study, we identified several differential candidate genes associated with Mg homeostasis via transcriptome analysis, including the xyloglucan endotransglucosylase/hydrolase (XTH) gene family. The XTH gene family is crucial for plant cell wall reconstruction and stress responses. These genes have been identified and thoroughly investigated in various plant species. However, there is no research pertaining to XTH genes within the M. alba plant. This research systematically examined the M. alba XTH (MaXTH) gene family at the genomic level using a bioinformatic approach. In total, 22 MaXTH genes were discovered and contained the Glyco_hydro_16 and XET_C conserved domains. The MaXTHs were categorized into five distinct groups by their phylogenetic relationships. The gene structure possesses four exons and three introns. Furthermore, the MaXTH gene promoter analysis reveals a plethora of cis-regulatory elements, mainly stress responsiveness, phytohormone responsiveness, and growth and development. GO analysis indicated that MaXTHs encode proteins that exhibit xyloglucan xyloglucosyl transferase and hydrolase activities in addition to cell wall biogenesis as well as xyloglucan and carbohydrate metabolic processes. Moreover, a synteny analysis unveiled an evolutionary relationship between the XTH genes in M. alba and those in three other species: A. thaliana, P. trichocarpa, and Zea mays. Expression profiles from RNA-Seq data displayed distinct expression patterns of XTH genes in M. alba leaf tissue during Mg treatments. Real-time quantitative PCR analysis confirmed the expression of the MaXTH genes in Mg stress response. Overall, this research enhances our understanding of the characteristics of MaXTH gene family members and lays the foundation for future functional genomic study in M. alba.

Genome-wide identification of XTH gene family in Musa acuminata and response analyses of MaXTHs and xyloglucan to low temperature

Banana (Musa spp.) production is seriously threatened by low temperature (LT) in tropical and subtropical regions. Xyloglucan endotransglycosylase/hydrolases (XTHs) are considered chief enzymes in cell wall remodelling and play a central role in stress responses. However, whether MaXTHs are involved in the low temperature stress tolerance in banana is not clear. Here, the identification and characterization of MaXTHs were carried out, followed by prediction of their cis-acting elements and protein-protein interactions. In addition, candidate MaXTHs involved in banana tolerance to LT were screened through a comparison of their responses to LT between tolerant and sensitive cultivars using RNA-Seq analysis. Moreover, immunofluorescence (IF) labelling was employed to compare changes in the temporal and spatial distribution of different types of xyloglucan components between these two cultivars upon stress. In total, 53 MaXTHs have been identified, and all were predicted to be located in the cell wall, 14 of them also in the cytoplasm. Only 11 MaXTHs have been found to interact with other proteins. Among 16 MaXTHs with LT responsiveness elements, MaXTH26/29/32/35/50 (Group I/II members) and MaXTH7/8 (Group IIIB members) might be involved in banana tolerance to LT stress. IF results suggested that the content of xyloglucan components recognized by CCRC-M87/103/104/106 antibodies might be negatively related to banana chilling tolerance. In conclusion, we have identified the MaXTH gene family and assessed cell wall re-modelling under LT stress. These results will be beneficial for banana breeding against stresses and enrich the cell wall-mediated resistance mechanism in plants to stresses.

Genome-wide characterization of the xyloglucan endotransglucosylase/hydrolase family genes and their response to plant hormone in sugar beet

Xyloglucan endotransglucosylase/hydrolases (XTHs) play a crucial role in plant growth and development. However, their functional response to phytohormone in sugar beet still remains obscure. In this study, we identified 30 putative BvXTH genes in the sugar beet genome. Phylogenetic and evolutionary relationship analysis revealed that they were clustered into three groups and have gone through eight tandem duplication events under purifying selection. Gene structure and motif composition analysis demonstrated that they were highly conserved and all contained one conserved glycoside hydrolase family 16 domain (Glyco_hydro_16) and one xyloglucan endotransglycosylase C-terminus (XET_C) domain. Transcriptional expression analysis exhibited that all BvXTHs were ubiquitously expressed in leaves, root hairs and tuberous roots, and most of them were up-regulated by brassinolide (BR), jasmonic acid (JA), abscisic acid (ABA) and gibberellic acid (GA3). Further mutant complementary experiment demonstrated that expression of BvXTH17 rescued the retarded growth phenotype of xth22, an Arabidopsis knock out mutant of AtXTH22. The findings in our work provide fundamental information on the structure and evolutionary relationship of the XTH family genes in sugar beet, and reveal the potential function of BvXTH17 in plant growth and hormone response.

Genome-wide identification and expression analysis of xyloglucan endotransglucosylase/hydrolase genes family in Salicaceae during grafting

BACKGROUND

Poplar (Populus cathayana)and willow (Salix rehderiana) are important fast-growing trees in China. Grafting plays an important role in improving plant stress resistance and construction of ornamental plants. It is found that willow scions grafted onto poplar rootstocks can form ornamental plants. However, this grafted combination has a low survival rate. Many studies have reported that the xyloglucan endotransglucosylase/hydrolase (XTH) family plays an important role in the healing process of grafts.

RESULTS

A total of 38 PtrXTHs and 32 SpuXTHs were identified in poplar and willow respectively, and were classified into three subfamilies. Tandem duplication was the main reason for the expansion of the PtrXTHs. Grafting treatment and Quantitative real time PCR (RT-qPCR) analysis revealed that five XTH genes differentially expressed between self-grafted and reciprocal grafted combinations. Specifically, the high expression levels of SrXTH16, SrXTH17, SrXTH25, PcXTH22 and PcXTH17 may contribute to the high survival rate of the grafted combination with willow scion and poplar rootstock. Subcellular localization identified that the SrXTH16, SrXTH17, SrXTH25, PcXTH17 and PcXTH22 proteins were located on the cell walls. Transcription factors (NAC, MYB and DOF) may regulate the five XTH genes.

CONCLUSIONS

This study provides a new understanding of the roles of PcXTH and SrXTH genes and their roles in grafting. Our results will give some hints to explore the molecular mechanisms of PcXTH and SrXTH genes involved in grafting in the future.

A Surprising Diversity of Xyloglucan Endotransglucosylase/Hydrolase in Wheat: New in Sight to the Roles in Drought Tolerance

Drought has become a major limiting factor for wheat productivity, and its negative impact on crop growth is anticipated to increase with climate deterioration in arid areas. Xyloglucan endoglycosylases/hydrolases (XTHs) are involved in constructing and remodeling cell wall structures and play an essential role in regulating cell wall extensibility and stress responses. However, there are no systematic studies on the wheat XTH gene family. In this study, 71 wheat XTH genes (TaXTHs) were characterized and classified into three subgroups through phylogenetic analysis. Genomic replication promoted the expansion of TaXTHs. We found a catalytically active motif and a potential N-linked glycosylation domain in all TaXTHs. Further expression analysis revealed that many TaXTHs in the roots and shoots were significantly associated with drought stress. The wheat TaXTH12.5a gene was transferred into Arabidopsis to verify a possible role of TaXTHs in stress response. The transgenic plants possessed higher seed germination rates and longer roots and exhibited improved tolerance to drought. In conclusion, bioinformatics and gene expression pattern analysis indicated that the TaXTH genes played a role in regulating drought response in wheat. The expression of TaXTH12.5a enhanced drought tolerance in Arabidopsis and supported the XTH genes' role in regulating drought stress response in plants.

CiXTH29 and CiLEA4 Role in Water Stress Tolerance in Cichorium intybus Varieties

Drought causes massive crop quality and yield losses. Limiting the adverse effects of water deficits on crop yield is an urgent goal for a more sustainable agriculture. With this aim, six chicory varieties were subjected to drought conditions during seed germination and at the six week-old plant growth stage, in order to identify some morphological and/or molecular markers of drought resistance. Selvatica, Zuccherina di Trieste and Galatina varieties, with a high vegetative development, showed a major germination index, greater seedling development (6 days of growth) and a greater dehydration resistance (6 weeks of growth plus 10 days without water) than the other ones (Brindisina, Esportazione and Rossa Italiana). Due to the reported involvement, in the abiotic stress response, of xyloglucan endotransglucosylase/hydrolases (XTHs) and late embryogenesis abundant (LEA) multigene families, XTH29 and LEA4 expression profiles were investigated under stress conditions for all analyzed chicory varieties. We showed evidence that chicory varieties with high CiXTH29 and CiLEA4 basal expression and vegetative development levels better tolerate drought stress conditions than varieties that show overexpression of the two genes only in response to drought. Other specific morphological traits characterized almost all chicory varieties during dehydration, i.e., the appearance of lysigen cavities and a general increase of the amount of xyloglucans in the cell walls of bundle xylem vessels. Our results highlighted that high CiXTH29 and CiLEA4 basal expression, associated with a high level of vegetative growth, is a potential marker for drought stress tolerance.

Transcriptomic mechanisms of reduced PM2.5-Pb retention in the leaves of the low-Pb-accumulation genotype of Chinese cabbage

Atmospheric fine particulate matter (PM_2.5) mainly contributes to Pb accumulation in the edible leaves of Chinese cabbage in North China. It was found that a low-Pb-accumulation (LPA) genotype of Chinese cabbage contained less Pb in leaves than high-Pb-accumulation (HPA) genotype exposed to PM_2.5-Pb. However, there are no data on the transcriptional regulatory mechanisms of foliar PM_2.5-Pb uptake by Chinese cabbage. The present study investigated the retention of PM_2.5-Pb in foliar apoplast and symplasm and the underlying molecular mechanisms of reduced Pb in LPA leaves. It appeared more Pb in apoplast and less Pb in symplasm of LPA leaves, whereas the pattern was opposite in HPA. There were 2646 and 3095 differentially expressed genes (DEGs) in LPA and HPA leaves under PM_2.5-Pb stress with clearly genotype-specific function, respectively. Furthermore, mRNA levels of XTH16 regulating cell wall thickening, PME2 and PME6 involved in cell wall remodification were significantly expressed in LPA, but not in HPA. Meanwhile, foliar PM_2.5-Pb stress downregulated expression of ZIP1, YSL1, and CNGC3 responsible for Pb influx to cell, and upregulated expression of ABCG36 regulated Pb efflux from symplasm in LPA leaves. These results improve our understanding to the mechanisms underlying foliar Pb uptake from PM_2.5-Pb at transcriptomic level.

Genome-Wide Identification and Expression Analysis of the Xyloglucan Endotransglucosylase/Hydrolase Gene Family in Sweet Potato [Ipomoea batatas (L.) Lam]

The xyloglucan endotransglucosylase/hydrolase (XET/XEH, also named XTH) family is a multigene family, the function of which plays a significant role in cell-wall rebuilding and stress tolerance in plants. However, the specific traits of the XTH gene family members and their expression pattern in different tissues and under stress have not been carried out in sweet potato. Thirty-six XTH genes were identified in I. batatas, all of which had conserved structures (Glyco_hydro_16). Based on Neighbor-Joining phylogenetic analysis the IbXTHs can be divided into three subfamilies-the I/II, IIIA, and IIIB subfamilies, which were unevenly distributed on 13 chromosomes, with the exception of Chr9 and Chr15. Multiple cis-acting regions related to growth and development, as well as stress responses, may be found in the IbXTH gene promoters. The segmental duplication occurrences greatly aided the evolution of IbXTHs. The results of a collinearity analysis showed that the XTH genes of sweet potato shared evolutionary history with three additional species, including A. thaliana, G. max, and O. sativa. Additionally, based on the transcriptome sequencing data, the results revealed that the IbXTHs have different expression patterns in leaves, stems, the root body (RB), the distal end (DE), the root stock (RS), the proximal end (PE), the initiative storage root (ISR), and the fibrous root (FR), and many of them are well expressed in the roots. Differentially expressed gene (DEG) analysis of FRs after hormone treatment of the roots indicated that IbXTH28 and IbXTH30 are up-regulated under salicylic acid (SA) treatment but down-regulated under methyl jasmonate (MeJA) treatment. Attentionally, there were only two genes showing down-regulation under the cold and drought treatment. Collectively, all of the findings suggested that genes from the XTH family are crucial for root specificity. This study could provide a theoretical basis for further research on the molecular function of sweet potato XTH genes.

Genome-wide characterization of the xyloglucan endotransglucosylase/hydrolase gene family in Solanum lycopersicum L. and gene expression analysis in response to arbuscular mycorrhizal symbiosis

Xyloglucan endotransglucosylase/hydrolases (XTHs) are a glycoside hydrolase protein family involved in the biosynthesis of xyloglucans, with essential roles in the regulation of plant cell wall extensibility. By taking advantage of the whole genome sequence in Solanum lycopersicum, 37 SlXTHs were identified in the present work. SlXTHs were classified into four subfamilies (ancestral, I/II, III-A, III-B) when aligned to XTHs of other plant species. Gene structure and conserved motifs showed similar compositions in each subfamily. Segmental duplication was the primary mechanism accounting for the expansion of SlXTH genes. In silico expression analysis showed that SlXTH genes exhibited differential expression in several tissues. GO analysis and 3D protein structure indicated that all 37 SlXTHs participate in cell wall biogenesis and xyloglucan metabolism. Promoter analysis revealed that some SlXTHs have MeJA- and stress-responsive elements. qRT-PCR expression analysis of nine SlXTHs in leaves and roots of mycorrhizal colonized vs. non-colonized plants showed that eight of these genes were differentially expressed in leaves and four in roots, suggesting that SlXTHs might play roles in plant defense induced by arbuscular mycorrhiza. Our results provide valuable insight into the function of XTHs in S. lycopersicum, in addition to the response of plants to mycorrhizal colonization.

Identification of the Xyloglucan Endotransglycosylase/Hydrolase (XTH) Gene Family Members Expressed in Boehmeria nivea in Response to Cadmium Stress

Xyloglucan endotransglycosylase/hydrolase (XTH) genes play an important role in plant resistance to abiotic stress. However, systematic studies of the response of Boehmeria nivea (ramie) XTH genes (BnXTHs) to cadmium (Cd) stress are lacking. We sought to identify the BnXTH-family genes in ramie through bioinformatics analyses and to investigate their responses to Cd stress. We identified 19 members of the BnXTH gene family from the ramie genome, referred to as BnXTH1-19, among which BnXTH18 and BnXTH19 were located on no chromosomes and the remaining genes were unevenly distributed across 11 chromosomes. The 19 members were divided into four groups, Groups I/II/IIIA/IIIB, according to their phylogenetic relationships, and these groups were supported by analyses of intron-exon structure and conserved motif composition. A highly conserved catalytic site (HDEIDFEFLG) was observed in all BnXTH proteins. Additionally, three gene pairs (BnXTH6-BnXTH16, BnXTH8-BnXTH9, and BnXTH17-BnXTH18) were obtained with a fragment and tandem-repeat event analysis of the ramie genome. An analysis of cisregulatory elements revealed that BnXTH expression might be regulated by multiple hormones and abiotic and biotic stress responses. In particular, 17 cisregulatory elements related to abiotic and biotic stress responses and 11 cisregulatory elements related to hormone responses were identified. We also found that most BnXTH genes responded to Cd stress, and BnXTH1, BnXTH3, BnXTH6, and BnXTH15 were most likely to contribute to the Cd tolerance of ramie, as evidenced by the substantial increases in expression under Cd treatment. Heterologous expression of BnXTH1, BnXTH6, and BnXTH15 significantly enhanced the Cd tolerance of transgenic yeast cells. These results suggest that the BnXTH gene family is involved in Cd stress responses, laying a theoretical foundation for functional studies of BnXTH genes and the innovative breeding of Cd-tolerant ramie.

The Arabidopsis TETRATRICOPEPTIDE-REPEAT THIOREDOXIN-LIKE (TTL) family members are involved in root system formation via their interaction with cytoskeleton and cell wall remodeling

Lateral roots (LR) are essential components of the plant edaphic interface; contributing to water and nutrient uptake, biotic and abiotic interactions, stress survival, and plant anchorage. We have identified the TETRATRICOPEPTIDE-REPEAT THIOREDOXIN-LIKE 3 (TTL3) gene as being related to LR emergence and later development. Loss of function of TTL3 leads to a reduced number of emerged LR due to delayed development of lateral root primordia (LRP). This trait is further enhanced in the triple mutant ttl1ttl3ttl4. TTL3 interacts with microtubules and endomembranes, and is known to participate in the brassinosteroid (BR) signaling pathway. Both ttl3 and ttl1ttl3ttl4 mutants are less sensitive to BR treatment in terms of LR formation and primary root growth. The ability of TTL3 to modulate biophysical properties of the cell wall was established under restrictive conditions of hyperosmotic stress and loss of root growth recovery, which was enhanced in ttl1ttl3ttl4. Timing and spatial distribution of TTL3 expression is consistent with its role in development of LRP before their emergence and subsequent growth of LR. TTL3 emerged as a component of the root system morphogenesis regulatory network.

Genome-wide identification of biotin carboxyl carrier subunits of acetyl-CoA carboxylase in Brassica and their role in stress tolerance in oilseed Brassica napus

Background

Biotin carboxyl carrier protein (BCCP) is a subunit of Acetyl CoA-carboxylase (ACCase) which catalyzes the conversion of acetyl-CoA to malonyl-CoA in a committed step during the de novo biosynthesis of fatty acids. Lipids, lipid metabolites, lipid-metabolizing and -modifying enzymes are known to play a role in biotic and abiotic stress tolerance in plants. In this regard, an understanding of the Brassica napus BCCP genes will aid in the improvement of biotic and abiotic stress tolerance in canola.

Results

In this study, we identified 43 BCCP genes in five Brassica species based on published genome data. Among them, Brassica rapa, Brassica oleracea, Brassica nigra, Brassica napus and Brassica juncea had six, seven, seven, 10 and 13 BCCP homologs, respectively. Phylogenetic analysis categorized them into five classes, each with unique conserved domains. The promoter regions of all BCCP genes contained stress-related cis-acting elements as determined by cis-element analysis. We identified four and three duplicated gene pairs (segmental) in B. napus and B. juncea respectively, indicating the role of segmental duplication in the expansion of this gene family. The Ka/Ks ratios of orthologous gene pairs between Arabidopsis thaliana and five Brassica species were mostly less than 1.0, implying that purifying selection, i.e., selective removal of deleterious alleles, played a role during the evolution of Brassica genomes. Analysis of 10 BnaBCCP genes using qRT-PCR showed a different pattern of expression because of exposure of the plants to biotic stresses, such as clubroot and sclerotinia diseases, and abiotic stresses such as drought, low temperature and salinity stresses.

Conclusions

The identification and functional analysis of the Brassica BCCPs demonstrated that some of these genes might play important roles in biotic and abiotic stress responses. Results from this study could lay the foundation for a better understanding of these genes for the improvement of Brassica crops for stress tolerance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08920-y.

The XTH Gene Family in Schima superba: Genome-Wide Identification, Expression Profiles, and Functional Interaction Network Analysis

Xyloglucan endotransglucosylase/hydrolase (XTH), belonging to glycoside hydrolase family 16, is one of the key enzymes in plant cell wall remodeling. Schima superba is an important timber and fireproof tree species in southern China. However, little is known about XTHs in S. superba. In the present study, a total of 34 SsuXTHs were obtained, which were classified into three subfamilies based on the phylogenetic relationship and unevenly distributed on 18 chromosomes. Furthermore, the intron-exon structure and conserved motif composition of them supported the classification and the members belonging to the same subfamily shared similar gene structures. Segmental and tandem duplication events did not lead to SsuXTH gene family expansion, and strong purifying selection pressures during evolution led to similar structure and function of SsuXTH gene family. The interaction network and cis-acting regulatory elements analysis revealed the SsuXTH expression might be regulated by multiple hormones, abiotic stresses and transcription factors. Finally, expression profiles and GO enrichment analysis showed most of the tandem repeat genes were mainly expressed in the phloem and xylem and they mainly participated in glycoside metabolic processes through the transfer and hydrolysis of xyloglucan in the cell wall and then regulated fiber elongation.

Genome-wide identification and expression analysis of the xyloglucan endotransglucosylase/hydrolase gene family in poplar

Background

Xyloglucan endotransglucosylase/hydrolase (XTH) family plays an important role in cell wall reconstruction and stress resistance in plants. However, the detailed characteristics of XTH family genes and their expression pattern under salt stress have not been reported in poplar.

Results

In this study, a total of 43 PtrXTH genes were identified from Populus simonii × Populus nigra, and most of them contain two conserved structures (Glyco_hydro_16 and XET_C domain). The promoters of the PtrXTH genes contain mutiple cis-acting elements related to growth and development and stress responses. Collinearity analysis revealed that the XTH genes from poplar has an evolutionary relationship with other six species, including Eucalyptus robusta, Solanum lycopersicum, Glycine max, Arabidopsis, Zea mays and Oryza sativa. Based on RNA-Seq analysis, the PtrXTH genes have different expression patterns in the roots, stems and leaves, and many of them are highly expressed in the roots. In addition, there are11 differentially expressed PtrXTH genes in the roots, 9 in the stems, and 7 in the leaves under salt stress. In addition, the accuracy of RNA-Seq results was verified by RT-qPCR.

Conclusion

All the results indicated that XTH family genes may play an important role in tissue specificity and salt stress response. This study will lay a theoretical foundation for further study on molecular function of XTH genes in poplar.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08134-8.

Identification and response analysis of xyloglucan endotransglycosylase/hydrolases (XTH) family to fluoride and aluminum treatment in Camellia sinensis

BACKGROUND

Xyloglucan endotransglycosylase/hydrolases (XTH) can disrupt and reconnect the xyloglucan chains, modify the cellulose-xyloglucan complex structure in the cell wall to reconstruct the cell wall. Previous studies have reported that XTH plays a key role in the aluminum (Al) tolerance of tea plants (Camellia sinensis), which is a typical plant that accumulates Al and fluoride (F), but its role in F resistance has not been reported.

RESULTS

Here, 14 CsXTH genes were identified from C. sinensis and named as CsXTH1-14. The phylogenetic analysis revealed that CsXTH members were divided into 3 subclasses, and conserved motif analysis showed that all these members included catalytic active region. Furthermore, the expressions of all CsXTH genes showed tissue-specific and were regulated by Al³⁺ and F^- treatments. CsXTH1, CsXTH4, CsXTH6-8 and CsXTH11-14 were up-regulated under Al³⁺ treatments; CsXTH1-10 and CsXTH12-14 responded to different concentrations of F^- treatments. The content of xyloglucan oligosaccharide determined by immunofluorescence labeling increased to the highest level at low concentrations of Al³⁺ or F^- treatments (0.4 mM Al³⁺ or 8 mg/L F^-), accompanying by the activity of XET (Xyloglucan endotransglucosylase) peaked.

CONCLUSION

In conclusion, CsXTH activities were regulated by Al or F via controlling the expressions of CsXTH genes and the content of xyloglucan oligosaccharide in C. sinensis roots was affected by Al or F, which might finally influence the elongation of roots and the growth of plants.