Cloning and characterization of a CCoAOMT gene involved in rapid lignification of endocarp in dove tree (Davidia involucrata Baill.)

Establishment and validation of a callus tissue transformation system for German chamomile (Matricaria chamomilla L.)

BACKGROUND

German chamomile (Matricaria chamomilla L.) is an important medicinal plant, and the essential oils in the flowers have various biological activities. Genetic transformation systems are important for plant quality improvement and molecular research. To the best of our knowledge, a genetic transformation system has not yet been reported for German chamomile.

RESULTS

In this study, we developed Agrobacterium-mediated transformation protocols for German chamomile callus tissues. This involved optimizing key parameters, such as hygromycin and cefotaxime concentrations, bacterial density, and infection and co-culture durations. We also performed gas chromatography-mass spectrometry analysis to identify volatile compounds in non-transgenic and transgenic callus and hairy root tissues. Furthermore, to compare and verify the callus transformation system of German chamomile, we transferred McFPS to the hairy roots of German chamomile. The results showed that the optimal conditions for Agrobacterium-mediated callus tissue transformation were as follows: explant, petiole; cefotaxime concentration, 300 mg/L; hygromycin concentration, 10 mg/L; and bacterial solution concentration, OD600 = 0.6; callus transformation efficiency was the highest when the co-culture time was 3 days.

CONCLUSIONS

Establishment of a high-efficiency callus transformation system will lay the foundation for gene function identification in German chamomile.

Mechanism of Stone (Hardened Endocarp) Formation in Fruits: An Attempt toward Pitless Fruits, and Its Advantages and Disadvantages

Stone (hardened endocarp) has a very important role in the continuity of plant life. Nature has gifted plants with various seed protection and dispersal strategies. Stone-fruit-bearing species have evolved a unique adaptation in which the seed is encased in an extremely hard wood-like shell called the stone. The lignification of the fruit endocarp layer produces the stone, a feature that separates drupes from other plants. Stone cells emerge from parenchyma cells after programmed cell death and the deposition of cellulose and lignin in the secondary cell wall. Generally, the deposition of lignin in primary cell walls is followed by secondary thickening of cell walls to form stone cells. This review article describes the molecular mechanisms and factors that influence the production of stone in the fruit. This is the first review article that describes the molecular mechanisms regulating stone (harden endocarp) formation in fruits. This article will help breeders understand the molecular and genetic basis for the stone formation in fruit, and this could lead to new and innovative directions to breed stoneless fruit cultivars in the future.

DiZF-C3H1, a zinc finger transcription factor from the dove tree (Davidia involucrata Baill.), plays a negative role in seed development and plant growth in Arabidopsis and tobacco

Low seed fertility seriously limits the survival and adaption of rare plant species. Here, we identified a seed-specific gene, DiZF-C3H1, from the dove tree and verified its function. Overexpression of DiZF-C3H1 caused retarded root development, delayed anthesis, abnormal floral organs, and deformed siliques in transgenic Arabidopsis lines. No offspring were obtained in transgenic Arabidopsis lines due to serious seed abortion. Therefore, we performed further verification in tobacco. Similarly, overexpression of DiZF-C3H1 retarded root development and reduced berry size and seed yield in transgenic tobacco lines. Moreover, although transgenic tobacco offspring were obtained, the viability of transgenic seeds was reduced and their germination was delayed. In addition, faded flowers were observed in transgenic tobacco lines. Taken together, DiZF-C3H1 was verified to play a negative role in root growth, floral organ development, and especially seed development in Arabidopsis and tobacco. This appears to be a deleterious gene for these model plants with high seed fertility. However, this function might be of special significance for Davidia, whose seed dormancy period is extremely long; DiZF-C3H1 might play a critical role in the distinctive reproduction strategy adopted by this rare and endangered species.

Genome-wide identification and characterization of caffeoyl-coenzyme A O-methyltransferase genes related to the Fusarium head blight response in wheat

Background

Lignin is one of the main components of the cell wall and is directly associated with plant development and defence mechanisms in plants, especially in response to Fusarium graminearum (Fg) infection. Caffeoyl-coenzyme A O-methyltransferase (CCoAOMT) is the main regulator determining the efficiency of lignin synthesis and composition. Although it has been characterized in many plants, to date, the importance of the CCoAOMT family in wheat is not well understood.

Results

Here, a total of 21 wheat CCoAOMT genes (TaCCoAOMT) were identified through an in silico genome search method and they were classified into four groups based on phylogenetic analysis, with the members of the same group sharing similar gene structures and conserved motif compositions. Furthermore, the expression patterns and co-expression network in which TaCCoAOMT is involved were comprehensively investigated using 48 RNA-seq samples from Fg infected and mock samples of 4 wheat genotypes. Combined with qRT-PCR validation of 11 Fg-responsive TaCCoAOMT genes, potential candidates involved in the FHB response and their regulation modules were preliminarily suggested. Additionally, we investigated the genetic diversity and main haplotypes of these CCoAOMT genes in bread wheat and its relative populations based on resequencing data.

Conclusions

This study identified and characterized the CCoAOMT family in wheat, which not only provided potential targets for further functional analysis, but also contributed to uncovering the mechanism of lignin biosynthesis and its role in FHB tolerance in wheat and beyond.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07849-y.

A Paeonia ostii caffeoyl-CoA O-methyltransferase confers drought stress tolerance by promoting lignin synthesis and ROS scavenging

Paeonia ostii is an emerging woody oil crop, but drought severely inhibits its growth and promotion in arid or semiarid areas, and little is known about the mechanism governing this inhibition. In this study, the full-length cDNA of a caffeoyl-CoA O-methyltransferase gene (CCoAOMT) from P. ostii was isolated, and determined to be comprised of 987 bp. PoCCoAOMT encoded a 247-amino acid protein, which was located in the nucleus and cytosol. Significantly higher PoCCoAOMT transcription was detected in P. ostii treated with drought stress. Subsequently, the constitutive overexpression of PoCCoAOMT in tobacco significantly conferred drought stress tolerance. Under drought stress, transgenic lines exhibited lower reactive oxygen species (ROS) accumulation, and higher antioxidant enzyme activities and photosynthesis. Moreover, the expression levels of senescence-associated genes were significantly downregulated, whereas the expression levels of lignin biosynthetic genes and PoCCoAOMT were significantly upregulated in transgenic lines. Similarly, transgenic lines produced significantly higher lignin, especially guaiacyl-lignin. These results suggest that PoCCoAOMT is a vital gene in promoting lignin synthesis and ROS scavenging to confer drought stress tolerance in P. ostii.

Isolation and functional identification of a Botrytis cinerea-responsive caffeoyl-CoA O-methyltransferase gene from Lilium regale wilson

In plants, genes involved in the Phenylpropanoid/monolignol pathway play important roles in lignin biosynthesis and plant immunity. However, their biological function in Lilium remains poorly characterized. Comparative RNA sequencing of the expression profiles of the monolignol pathway genes from fungi-resistant species Lilium regale after inoculation with Botrytis cinerea was performed. One upregulated caffeoyl-CoA O-methyltransferase gene, LrCCoAOMT, was cloned for functional characterization by reverse genetic methods. LrCCoAOMT encodes a putative protein of 246 amino acids and is highly expressed in stem tissues and responsive to salicylic acid (SA) signaling and B. cinerea infection. LrCCoAOMT was largely directed to the cytoplasm. LrCCoAOMT overexpression in Arabidopsis resulted in an increased lignin deposition in vascular tissues and conferred resistance to B. cinerea infection in transgenic plants. Transient transformation of LrCCoAOMT in nonresistant Lilium sargentiae leaves also identified the defense function to B. cinerea. In addition, transcript levels of genes involved in the monolignol and SA-dependent signaling pathways were altered in transgenic Arabidopsis, suggesting that LrCCoAOMT might play vital roles in the resistance of L. regale to B. cinerea related to the levels of lignin and the regulation of SA signaling. This is the first report to functionally characterize a CCoAOMT gene in Lilium, a potential molecular target for lily molecular improvement.

Cloning and functional analysis of three aphid alarm pheromone genes from German chamomile (Matricaria chamomilla L.)

German chamomile (Matricaria chamomilla L.) is one of the most ancient medicinal species in the world and terpenoids from their flowers have important medicinal value. We cloned three sesquiterpene synthase genes, McGDS1, McGDS2 and McGDS3, and performed sequence alignment and phylogenetic analysis. The encoded proteins possess three conserved structural features: an RRxxxxxxxxW motif, an RxR motif, and a DDxxD motif. McGDS1, McGDS2 and McGDS3 were confirmed to be (E)-farnesene synthase, germacrene D synthase, and germacrene A synthase, respectively. Subcellular localization revealed diffuse GFP reporter-gene signals in the cytoplasm and nucleus. qPCR indicated that McGDS1, McGDS2 and McGDS3, were more highly expressed in young flowers than in old flowers and the expression was highly correlated with amounts of the end-product essential oils ((E)-β-farnesene, germacrene D and β-elemene), with coefficients of 0.76, 0.83 and 0.68, respectively. We also established a transformation system for chamomile hairy roots. The overexpression of McGDS1, McGDS2 and McGDS3 resulted in γ-muurolene accumulation in hairy roots. The activity of three aphid alarm pheromones here forms the molecular basis for the study of the biosynthesis and regulation of volatile terpenes. Transformation of chamomile hairy roots provides a simple system in which to study terpene biosynthesis in chamomile.